Jeff Perrin

Oct 202007


Besides building a fast and cool looking 2008 WRX, we had a goal to showcase a turbo that I think should be the most popular for the normal guy thinking of a turbo kit for his 2.5L Turbo motor. The GT3071R!  This turbo gets overlooked quite often.  It easily makes 350WHP on an STI, and on race fuel/Water injection 400WHP can also be had easily.  The GT3076R (the more popular turbo) is also good for these numbers, but can easily support an extra 50WHP beyond those numbers. So why not just go with the bigger turbo, it makes more power???  Response!  The GT3076R turbo (given similar dyno loads and same turbine AR€™s) spool about 700RPM later than the GT3071R. For an Autocross guy that wants a nice responsive turbo, and doesn€™t care about making over 400WHP the GT3071R turbo is for them.

To add to all that, this test was done with a catalytic converter. While the stock car has two of them, and to keep it 100% legal it needs two, one cat is good enough to pass the tail pipe test and to keep the ECU happy.  But still not legal, just need to make that clear.  Also with the fuel pump issue we had, we would be putting the OEM fuel pump to the test.

The results below are for a GT3071R with a .82AR housing. The smaller .63AR housing will be tested at a later date to show the difference in HP and responsiveness.

We had just made a trip to LasVegas to attend the Street Tuner Shootout event at Spring Mountain. This was the debut of the car, and we had basically no time to tune the car, except driving it around the track.  Sounds scary but with the Hydra ECU on Autotune, the AFRs were stable and safe. With 4 good sessions of tuning at 16psi, the car was running great.  But how much power were we running?  After the car was setup on the dyno, the first runs were showing at 16.7PSI, we were hitting 320WHP and  340ft-lbs.  People were asking us at the track how much we thought we were making, and guess of 320 was right on!


Before we get too far, its important to mention that Hydra came through with a custom ECU for us for this event.  Hydra put together 2 special harnesses, one that uses the stock ECU to drive the dash and one that did completely away with the stock ECU.  The later didn€™t work as the ECU has an immobilizer built into it, and it wouldn€™t let the car start.   So the pass through version was used, and installed in the car.  The Hydra on this setup fits in the glove box which is a nice clean and tidy place for it.


Tuning Time

While I have tune a bunch of cars with the Hydra, I had Tim Bailey of Surgeline tuning to come by and help out.  Tim has been tuning cars across the country by himself for about 6 months, and turned it into a full time job. He is also supplying us with our custom tuned maps for our AccessPORT program.  Yes if you haven€™t seen that PERRIN is selling a COBB part, we are!  The AP is the best ECU flash tool, so why not sell it!  Anyway as seen above, the Dyno we bought is a Dynapack, which is a great tool for our R&D stuff.  Its great for repeatability and for providing HP numbers that don’t read too high or too low.

Base Run

The difference between these two runs was a couple three degrees of timing from 5500RPM on up.   40WHP with a few degrees is somewhat expect with the detuned nature it was in.  With further fueling/timing changes and adding boost along the way we easily got to our 350WHP goal. Ya, like we were going to stop there!

The fueling seemed to make the biggest difference in power, not timing.  Timing wasn€™t really messed with a whole lot until we turned the boost up to 20psi.


21PSI, and getting close to 400WHP!

Like I somewhat expected with this smaller turbo, we would get to a point where timing would really having be retarded and fueling would get richer. The sweet spot was right at the 19psi range, where we saw the most consistent and least noisey (knock) runs.  We turned up the boost to get some good numbers, and while these were reliable runs, the boost was turned back down to 19psi, and left alone.


The final results are pretty good in my opinion. We did start to run out of fuel with the pump. Anything above 20psi and about 6500 RPM were having to add a lot more fuel.  The Hydra€™s Fuel map had a €œFuel Nipple€ as Tim called it at these upper RPMS and boost ranges.  Now that we have more time, a Walbro will surely be dropped in there and retuned on the dyno.  Most likely this will wait for the water injection install and tune.



The boost curve of the GT3071R with .82AR is very good and responsive. The above graph shows the boost curve using the WG spring (16psi) and a PERRIN MBC for the increased boost.  18psi showed a near perfectly flat boost curve (I guess curve isn€™t the right term, boost flat??) As we increase the boost, the €œcurve€ became more of a slope showing the turbo€™s efficiency starting to drop and looking at a compressor map it makes sense.  Garrett says the turbo is good to 475 Crank HP which we were getting close to at the 380WHP mark.

Sure enough, from about 6200RPM on up and 21psi, power started to drop and it was harder to keep the engine quieter.  Interesting, torque peak occurred right where is should according to the graph, right in most efficient part of the map.


Here is the GT3076R .82 graph over laid from our shop Limited STI, and the GT3071R w/.82.  As you would expect from a slightly smaller turbo, more responsive, quicker spool, torque peak is earlier, but top end power not there.  As cool as it is, to have a big huge turbo on your car, I thinks it cooler to have a more drivable car!  This car feels great on the street.  Just the right amount of power, and the 5spd (with longer gearing) really likes this turbo.

Here is the list of parts installed on the car.


FMIC, Rotated turbo kit (GT3071R) with Cat Installed, 3€ Catback Exhaust, modded injectors, Fuel rails.

Other Contributing Brands

Tial 44mmWG, Hydra Custom 2008 ECU, H&R Custom coil overs, Konig Feather Wheels, Advan Neova tires

Look for the Water injection test soon!















 Posted by on October 20, 2007 Dyno Test & Tune, Project Builds, Turbocharger Testing Tagged with: , , , ,
Oct 172007

It’s a love hate relationship with any new model of car that comes out.  You either love it, or hate it, but eventually it grows on you.  I personally love the hatchback look from the side, and front, but the back is a little scary.  But a few simple things can fix that.  Getting rid of the chrome parts for painted or black out parts is a huge part of the formula.  Then lower it a bit with some nice wheels, and the car really starts to pop.

We have had our car for a couple months now, and we figure we would show you some of the progress we are making, and show our path to getting ready for its public debut at the 2008 Street tuner challenge.  So what would we be building for the 2008 WRX show car?? Well, everything!  The formula to build the show car is simple, turbo, FMIC, turbo back exhaust, fuel system that would support 500WHP, bigger swaybars, coilovers, and nice sticky wide tires, and good engine management.  While this list is easy to create in words, to create physical parts and do in about 2 weeks is the hard part.

Our car started life out as a 2008 WRX with the premium pack, and a whopping 14miles on the tripmeter.  Because they were hard to come by at the time, Subiesport Magazine used our hatchback and sedan for the latest Subiesport issue. Pics can be found HERE!

While we just moved into a nice big new building, our “Shop” was still at the old shop.  While this was a pain in the butt to drive back and forth, it was nice to have no distractions, and peace and quiet. While the shop was a little sparse, it had all the essentials to create everything we needed.



First off the exhaust. Not much to do here other than make a 3€ system thats quite!  Like our other exhaust systems, 3€ mandrel bent 304SS tubing was used, along with a straight through 3€ muffler.  Even though this was a prototype, it would be seen by many people so I end up polishing the tubing to represent what the final product would look like.


OEM midpipe bolted to PERRIN 2008 WRX Muffler.  This makes the car sound very mellow, but that cool Subaru Boxer sound finally starts to come out.


In some of the pics you will notice the system is bolted to an OEM exhaust.  This is a new feature we are trying to incorporate into a lot of our new exhausts.  This allows then end user to buy just the muffler, for some more sound, or buy just the center section to get some power, but keep things super quiet.



Another feature everyone will see in every exhaust system coming out is a V-band connection. This is a great way to make the system easier to package and provide an adjustable and gasketless connection.

The exhaust for the 2008 WRX is very different than any other Subaru in that the muffler transversely mounted.  While this adds some more complexity to the system, it adds a new look to the back of the car.  Now you can see the side of the muffler and the huge 3€ tubing.  Subaru obviously did this to cut down space needed behind the rear wheels to help shorten the car.




This shot represents what you might see driving down the road from behind.


From the back of the car, the muffler and the 3″ tubing really shows up.  Can’t wait to see what we can do with the STI!


On a side note, all the emissions related items (like the charcoal canister, and evap control solenoids) are moved to the inside of the car under the trunk’s floor.  Again Subaru moved this more toward the middle of the car to get more weight centrally located in the chassis.  One more note, the gas tank is under the back seat, not behind it!  Again more weight moved to the middle.  All of this starts to makes sense as the car (in stock form) seems to rotated better and handle better than previous models.


A set of PERRIN headers were used which are proven to gain HP across the RPM and increase spool RPM. The only difference is I coated the with VHT 2000 degree ceramic paint.  I have been using this product on the last few projects with great success.  Its simple, just clean the part really well, and spray it like paint.  And for $8 a can  you can€™t go wrong.  While I was coating the header, I figured I would coat the exhaust housing, and uppipe to the turbo kit.




Ya, who cares, no one will see it, but for a couple minutes of work, it made for a nice picture!


While Subaru has done some things to make the car handle better out of the box, Subaru has left some room for improvement.  Beauty with this car is there is lots of room to put some nice wide tires on it.  We could have gone with 255 easily with the correct offset and a little more time.  This is something we will be working on very soon. But 245 wide tires on this car is perfect for zero issues with rubbing.  Its kind of like 225s on the GD body. I just can€™t wait until the 2008 STI comes out!  Dare I say 265 or 275 with no issues???   So what kind of 245€™s would we use? We went with, what I feel to be the best street performance tire around, Advan Neova€™s.  They are not quite R compound, but very sticky, and good enough to drive on all year round, and good enough for some light track days.  Plus Yokohama hooked us up with set for this event.  The only problem was when the tires arrived.  To keep the tires connected to the car, we used some Konig Feather wheels. These are just over 17lbs for a 17″, and are very reasonably priced.

Starting at the front of the car, the front sway bar and end links fit perfect from the WRX/Legacy GT.  We chose to go with a 22mm front bar to help balance the rear sway bar we were building.  After driving the car, we might even be putting the 25mm on the front.  From there our Legacy GT PSRS plopped right into the control arms.  Yes, the 2008 WRX has those stupid super soft rubber rear control arm mounts.  This was a huge improvement to the handling as expected, and I think will be one of the most important suspension items for the new 2008 WRX/STI/LGT.  Those of you that have this part on their LGT will understand why I say that.

Onto the rear!  Of course we are going to build a rear sway bar, but what size???  Well the OEM bar is a whopping 15mm huge, so of course we are making one. But why did Subaru make it so small?  Many people will ask this question and thing that Subaru wants to make the car understeer more to suite more of the general public.  But after some measurements, Subaru was going the right way, more oversteer!  The OEM 19mm GD body rear sway bar, has an effective rate of 85lbs-in, compare this to our 22mm rear sway bar which has a rating of around 240lbs-in on the soft setting.  The new 2008 OEM 15mm bar is rated at around 130lbs-in, so its stiffer!  How can this be, simple the bar is shorter, and the leverage arms are shorter.  Going with a 17mm bar would make the effective rate about 215lbs-in, which might seem like enough.  But the STI is about to come out and I am sure it will have a larger(or stiffer) bar than the WRX, because it has in the past.  For us, this wouldn€™t be enough, so we went with a 19mm and made it with 3 holes. One hole stiffer, and one hole softer.  This made 3 rates, which vary from 260lbs-in, 340lbs-in and 440lbs-in.  This allows for settings that can be a mellow change from stock to a change that is more than 3 times stiffer than stock.  And the different settings are very noticeable.  The softer setting is a nice feature, as this will allow customers to work up toward the super stiff setting.

A prototype 2008 WRX rear swaybar was created, using the OEM bends, and some special laser cut ends.  This was sent off to be red powder coated and was had a couple of days later.  While installing the sway bar, we threw in one our larger volume diff covers.

All of these parts wouldn€™t really make much difference unless we could lower the car and stiffen up the suspension. This is the one thing that I don€™t like about the 2008 car, its€™ soft suspension.  This might be because I am used to driving cars with stiff suspension, and it had been a while since I had been in a WRX, but either way its too soft.  But that is a good thing as this gives us something to improve upon.  We are a long time dealer for H&R, so we turned to them for coilovers. Of course there is nothing off the shelf that would work so we had them send us a few kits to try to make something work. In the end the exact combination of parts is kept secret, but it worked out great. We could now lower the car to a level that was functional, and looked great.  This is when the car really started to look good, and really started to handle good.  The suspension was dialed in, except for an alignment.  While you should never lower a car and not get it aligned, time was becoming an issue, and it just wasn€™t going to happen.

build_08wrx_hrwrxrearcoilassemblyThe custom built H&R coilover all assembled and ready to drop in!

These really look sweet on the car!


I know, its not the most glorious picture, but this is a nice feature of the new 2008!  Now instead of lowering a car in under an hour, i am thinking under a half an hour.


So what would power our PERRIN show car?  Of course we would not be showing off our car with a stock turbo, or stock location turbo, so the obvious choice is a PERRIN rotated turbo kit. But which turbo is the question.  If look at the internet, everything is about the GT3582R turbo. While this is a great turbo to make big power with, and it gets lots of press because it is a widely used BIG turbo, its not my personal choice.  The last two cars i had were very responsive, and i had grown to love that.  There was no way I was going to go with some laggy GT3582R, that is no fun and makes for a crappy autocross/street car.  The GT3076R is another very popular turbo, and we have built plenty of these kits on cars, so that is a boring choice. The turbo for me is the GT3071R, a bit smaller, bit more responsive, and still able to make 400WHP.  We always tell people that buy the smallest turbo that supports your HP goals, and while our show cars never really follow these guidelines, this one would be!  We would showcase the power that can be made on pump fuel and then on water injection.


Installation of the turbo kit involved creating a new downpipe which is longer and modified to clear the fire wall. This change in the downpipe also makes for a turbo fitment for the Legacy GT, so be on the lookout for that also.  The single most important part of the turbo kit changes was adding a CARB approved catalytic converter to it.  Another important thing we like to do is prove that you can make power with cats.  Many people out there think that the only way to make power is by getting rid of cats.  This is not the case and with our last couple of PERRIN project cars, we had cats installed, and they both still made great power.


With the rotated turbo kit being installed on the 2008, we quickly discovered that the intake system had to be completely changed. So a few 3″ bends, welding, and more of that red wrinkle finish! Like our other new turbo kits, the filter was located in the fender well area to get the freshest coolest air possible. This is another theme you will see from us. More cold air intake systems.  But before we go and build that, we need to finish the front mounted intercooler pipe to ensure it all fits together.


The starting point to the FMIC is getting the intercooler mounted to the car.  Starting with a Legacy bumper beam from our LGT intercooler, I quickly found that this wouldn€™t, although it was close.   Couple of simple cuts, some welding, and beam done.


In order to get the intercooler to fit, I had to modify some of our WRX tanks to allow it to fit tighter to the beam.  I just grabbed a set with no holes and redrilled them where i needed it.


This is an angle most people don’t see with our intercooler tanks.  Notice the nice smooth insides, not gonna see those ever again!




With the core mounted to the chassis, plumbing was next.  Every tube on the 2008 WRX FMIC is completely different than any of our other FMIC€™s, and in an effort of time the prototypes we made would have to be made to look like the final product.  A little welding, grinding and off to the powder coaters they went.  But before they left we finished the turbo kit intake piping and sent all of it out at the same time.  A week goes by and they showed looking perfect, STI wrinkle red!





Now we can finish the intake system! Just like the boos tubes, the protos had to become the final product, so more welding and grinding!




Its a tight fit, but the filter does fit down there very nicely.


Of course to support the potential power, we need fuel.  We would be using our high flow fuel rails and modded injectors.  The modded injector thing still is not very well acknowledged in the Subaru world (even though they have been around for a few years).  We have had very good success with this simple and very effective way to increase the size of the injector, so like the last 5 cars I have built this one would be using them also.  The 2006 WRX+ injectors are a top feed style that in stock form flows 540CC/min of fuel.  But like all the other Subaru top feed injectors, these for 800cc/min when modded.   Many people claim that these injectors have bad spray patterns, and cause poor fuel economy. This is just not the case, and people that tell you this are people that have not used them before. Then of course the good old Walbro Fuel pump would be used in place of the OEM fuel pump which probably doesn€™t flow enough to make anywhere near 400WHP.

With the intake manifold removed, and rails installed, it was time to install the fuel pump.  Should only take an hour, right?   Above I mentioned that Subaru moved the tank under the seat but this was discovered during this part of the installation. First I pulled the back of the car apart to find that Subaru shoved all the emissions stuff where the fuel pump used to be. This is where I found the pump under the seat.  Take note that, before you install a fuel pump, make sure that you just didn€™t fill up the night before. This is messy!! But it does make the shop floor really clean under the car!

Now I have not done an install of a fuel pump on a legacy GT, but how hard could it be??


Well it all would have worked out just fine, but the only pump we had I broke off the nipple from the output fitting, while installing the o-ring adapter from the OEM pump.  Since we didn’t have one sitting around, and we were strapped for time, we would be putting the OEM fuel pump to the test!  Could it do 400WHP??


The only way this whole car will run is with some good engine management.  We turned to Hydra again for a custom made ECU for the 2008.  Andrew sent us 2 harness to try out on the car.  The first one was a harness that completely did away with the OEM ECU.  This would have worked fine, but all these new cars have immobilizers which will not let the ignition switch work without the OEM ECU being turned on.  So the second harness was a special pass through harness that kept the OEM ECU in place.  I created a base map using Hydra€™s 2006 WRX base map and a fuel map from tune a long time ago.  The car fired right up and it was time to take it for the maiden voyage!


The Hydra has a MAP Sensor built into the ECU itself, so it was necessary to run a hose into the car.





The Hydra is installed in the glove box, and the pass through connector is under the carpet.



The car was finally done, and with a couple days to spare. Now it was time to pack and get some sleep.  Wait, there still is the outside of the car!!  When ever we do graphics on a car, things just seem to work out.  Digital camo seemed to be a popular thing this year, so lets do something like that John Herring said.  This goes great with the shirts he just made and should be pretty cool looking.   John started cutting out random square shapes a few colors, and things just started falling into place.  We used matte black, glossy black, and red.  As shadows appear, and the lighting changes, the 3 different colors change and produce a totally different looking car.  While these pictures show the basic sceme, they don€™t show how cool it looks in person.


And just like most projects on a tight time schedule, we got her done just in time€¦..except for the tires.  While we carefully watched our tracking number for the tires the week prior to leaving, we started to wonder why they hadn€™t moved from California for a few days.  A quick call to Yokohama, and they said they screwed up and had to Next day air some tires.  No problem, it just meant the day before we left, we would be running down to Americas tire and getting some tires installed on our Konig Wheels. While we patiently watched the tracking number again, Monday comes and nothing!!   They didn€™t get picked up until Monday!! DAMN!  Ok, this just meant, we would be getting tires mounted the day we were leaving. Ok, its tomorrow, we are all stress out about the trip, and again we are watching the tracking number (not very confident in what its saying).  After the 3rd Fedex truck, finally tires!!  Wait, how many tires does a motorcycle take. Ya, TWO tires, that is what we got!!  Alright, this is not good.  Again there was a shipping issue with the tires and 2 more were shipped out but this time shipped to an Americas Tire in Las Vegas.  We would just have to have them installed there once we rolled into town.

Since we left about 12 hours later than we wanted to we decided to drive straight from Oregon to LV without stopping in Utah like we always do.  The rest of the story is pretty boring until we finally got to the track.  We went into this event knowing that we were not there to win, but rather test the 2008 WRX, and show it off to the public.  I think we did a good job, as finally I started to hear people say €œI can€™t belive that is the 2008 WRX!€.  Proof that we did a good job of building the car.   With the worry over regarding what the public might think, a new worry was starting to churn my stomach. TRACK TIME!!




You might think that we have time to do lots of track days every year, but this has not been the case for the last few years.  While I wasn€™t really worried about crashing or anything like that, I was worried about the car and how it would perform.  Mainly because there was no alignment, no one had a tire gauge or pump, and the ECU was only street tuned with a few full throttle runs.  Because of the state of tune the car was in, and those things said, overall the car felt great. It was pretty fast and running 16psi of boost it felt like a 350WHP car, and spooled around 3700RPM.  I was pretty happy as we  I could tell there needed to be an alignment.  With visually 0 to 1 degree of negative camber, and who knows what toe in or out it had, it had mild under steer in the tight twisty corners of Spring Mountain.  The car kept up with some of the faster EVO€™s and other random cars at the track.  For a session or 2, I was going faster than an Ariel Atom, but I think he was taking it easy, as this car should have blown everyone away.  Over all the car was pretty fast, but bringing the car to a haltNow with some seat time at the track, and a new alignment, this car might be somewhat competitive.  Maybe you will see it at the upcoming Redline Time Attack.

After the event, we felt great that the car was very well excepted by the public, and that it did just fine around the track.  But like all events, nothing ever goes perfect, and the only real issue we had, was a box in the trailer coming loose and landing on the car.  Bummer!  Our good buddy Jason can take care of this no problem.



So how much WHP did our car make at the track??  Just before we left, we took delivery of a dyno (yes its been a long time coming), but there just wasn€™t time to set the car up and do a base run, so it would have to wait until we get back.  Well we are back and the results were very surprising.  As expected the GT3071R makes a little less HP than a GT3076R, but spools quicker.  This was the reason why I chose this turbo, better response for autocrossing and normal driving.  The car makes almost 340Ft-lbs of torque, and 320WHP.  This was at the 16psi we ran at the track, and no wonder why we were keeping up with cars we thought were way faster.  When tuned to 18psi we made 365WHP, and 375ft-lbs of torque, while this is a good safe place to leave the car for engine durability issues, we have to push the car a little to see where this turbo starts to loose its breath.   At 21PSI, we made 385WHP, and 390FT-lbs.  Plenty of power for a street car!




Besides wait for an STI to come our way, this car needs a wing badly!!  Wait till you see what we have in store!!  Besides the wing, the car needs a little more love to get the suspension dialed, and I think its ready for more competitive track time.  We will just have to wait an see if it makes it to the Redline Time Attack!


While all these parts were created for our 2008 Show car, what would we be building for our catalog of parts??  Well, everything!!  All of these items along with our normal mix of parts are all in development and should be ready by the end of the year.  This is of course the new parts that had to be created, but there are many current parts that fit the 2008.

What did we have already for our build?

Front swaybar, front end links, fuel rails, injectors, PSRS, downpipe (for stock turbo, but not used), R160 diff cover, WRX short shifter, Shifter bushings, Crank pulley, EBCS, VTA and Recirc BOV€™s, gauge pods

What did we have to build?

FMIC, turbo kit, rear swabyar, rear endlinks, turbo back exhaust,

What parts we plan on making.

Sub frame brace, rear diff lockout, rear control arm bushing replacements, intake systems for OEM turbos, PERRIN custom tuned AccessPORT systems,

Parts installed on our show car.

FMIC, turbo kit, exhaust system, intake, PERRIN parts installed
PERRIN 2008 WRX GT3071R rotated turbo kit
PERRIN 2008 WRX Rotated turbo intake
PERRIN 2008 WRX 3€ Turbo back exhaust system
PERRIN 2008 WRX Positive Steering Response System
PERRIN 2008 WRX 19mm sway bar
PERRIN 2008 WRX Endlinks
PERRIN 2008 WRX Short shifter and Shifter bushings
TIAL 44mm Wastegate
Custom Hydra standalone ECU
Custom H&R Coilover
Konig Feather black wheels
Advan Neova 245/40/17s

Look for more information about the 2008 over the next few weeks!  Feel free to call us with any questions about 2008 Products or fittments.


 Posted by on October 17, 2007 Project Builds Tagged with: , , , , , ,
Aug 172007

This is an Nasioc Post we made regarding our older T31 turbo kits and changes we made to make the kit better.


First off fitment issues with the PERRIN turbo kit, are not common. While we have had issues time to time, we have taken care of those who had them.  I should say we have taken care of those who have called us and explained their problem.  There are a lot of our kits out there, and of course when there are problems, people say €œHey I have a problem€, weather by calling or by posting on forums. Those who don€™t have problems, generally go happily on their way, and never say a word. So while it seems like a lot of kits don€™t fit, this is just not the case.  We have many many satisfied customers and dealers who have complimented us on our kits, and how well they do fit.

While this is a hard part to install, we do get calls and comments about parts that are not fitting together well.  Generally the customer just hasn€™t adjusted something correctly, or installed things out of sequence.  To combat this we have changed instructions, and how the kit is €œpre-installed€, which has help quite a bit.  Secondly we have taken extra measures to ensure each kit fits together perfectly before it leaves the building. This means that the uppipe and DP have both bee fit together to a turbine housing and to the WG to ensure all pieces mate together properly.

Complaints of fitment with WG v-band are very common.  This is because this connection is very, very precise and it being off a little is very easy to spot.  This concern is easily fixed by customers following the directions and preassembling the kit outside the car. Then you are not dealing with trying to fit and align it in tight quarters.  As much as going to a 2 bolt type flange or WG would solve some problems, this is not something we are going to do.  The compactness, and performance benefit of the larger 44mm WG is well worth it.


Originally we made our kit somewhat universal to other FMICs.  While the connection from the turbo to the FMIC can be made, it was a little tricky to get just right.  With our current kits we are shipping we simplified this quite a bit with a single Silicone hose that goes from the turbo to the FMIC connection. This Jog eliminates extra couplers, and pipes that caused some issues.



Lets go over a couple things with the housings.  Like I have said many times before, and have shown many times before, there is no difference in the housings.  We choose to use the housing we did (a long time ago), as this housing was much more compact, and was readily available from our turbo supplier. These are the T31 exhaust housings people are referring to. These housings are a T3 inlet and have a short 2.5€ outlet.  The newer Garrett GT housing has the same T3 inlet but a longer 3€ outlet.  With out saying anymore, people jump to the conclusion that the 3€ is better as it is bigger, because in a turbo exhaust system bigger IS better.  You have to look at both housings and understand what makes them different, not better.  First off the turbine wheel inducer for all these turbos are smaller than 2.5€, which means that in order for it to get to 3€, some flaring is done.  Its in this flaring where things vary from the T31 to the Gt housing.

The T31 housing basically has no flare (inserter Office Space joke here).  The end of the turbine wheel is very close to the flange where the DP bolts to.  Our DP bolts to this and starts at 2.5€ then quickly is flared to 3€.

The GT housing is very long so it goes from the turbine wheel to the 3€ oulet in a couple of inches.  Basically accomplishing the 3€ OD in the same distance as our kit with the 2.5€ outlet.

Since we have a Garrett Engineer assigned to us of course I proposed the question whats the difference, his exact response below.
€œWe have never run a test between the two housings for that exact turbine
wheel.  (I asked hims specifically on the GT3582R ) We did do a test a different turbine wheel and the performance for the 2.5″ housing was slightly less (on the order of the uncertainty of the measurement).  I would suspect you would observe no performance difference.€

Add to that are some pictures showing the differences:




Proof is in the pudding!!!!!! (Not sure where that came from but I am sure Wikipedia has something on it) There are a couple of naysayers out there about this housing, but they are not comparing apples to apples.  If this housing was so bad, then we would see some HP or spool differences in cars with GT housings, but this is just not the case.  We have cars with Gt3076R w/.82 turbos and they spool around 4000, and make about 400WHP on pump gas, and 460 on race gas.  This is the same thing seen on the GT housings, and in fact a somewhat local customer had one our kits modded for the GT housing, and his car spooled just like others, and made about the same HP as others.  If this T31 exhaust housing was a choke, or a hindrance to the WRX€™s making power, I think there would be a lot more people complaining about how their car doesn€™t make enough power.


Regarding the support brace. This is a part we have developed a year or 2 after we release our kits. The brace is a very simple and effective brace that limits the €œpossibly€ damaging left and right vibrations.  We say possibly as there are many turbo kits out there with no brace and have no issues.  Because of the way the kit bolts to the car, it is somewhat braced in its self. This is why so far, there is no need for one.

We currently have braces in stock for the old GT35R, but since our kit is changing, we will not have braces for the other turbos for a while.

That should clear up peoples concerns about the kits performance and fitment issues.

The Changes!

Now onto the changes we have and are making.  We are switching to the GT housing!!  Since there are those who €œThink€ the T31 is not as good as the GT housing, what better way to satisfy everyone than to change to the GT housing!  While we feel there is ZERO benefit in HP or spool, the other benefits are supply issues.  Since the inception of our turbo kit, we have gone direct with Garrett, and getting the newer housings is much easier, as they are an off the shelf part.  So switching housings forces a few things like DP and uppipe changes, which we have added more room around the WG, and clearance around the chassis. While our kit will hang a little lower, it will eliminate any issues with clearance with different motor mounts or slight variation in cars.


Blow thru boost tube

This is a part we have been selling for a while now, but it is change to the new kit because you HAVE to have it (or a stand alone ECU).  We have found that this part makes tuning simpler, eliminates issues with stop and go traffic (making the MAF see high temps), nearly eliminates rich or lean conditions with leaks in boost tubes, or intake hose.

Intake system.

This is an item that was made for this future kit, as well as the old kit.  No more silicone!  Well at least big pieces of silicone.  The new intake system is now a cold air tube that fits down in the fender well.  While this part is a little trickier to install, it really cleans up the engine bay.


I like guys at Crawford performance, and in no way do we say they make a bad part.  Both of us have great parts that fit people€™s needs. Their kit requires their FMIC, ours fits with our FMIC and other OEM turbo fitment types.


Your spool characteristics are probably right in line with what you would have had, if you just got a new turbo from us.  Clark makes it seem like there is some huge difference, and this is just not the case. But going from a 4000-ish spool and adding 800-ish isn€™t that much different when it comes down to it. Also with the hit of power you have, it makes up for that loss of power right before the boost comes on.

Remember the T31 is a Garrett part, and its machined to fit the volute and the profile of the turbine wheel just like the GT housing.  I agree that it would be nice to put the T31 housing debate to rest, but it will go on forever, as long as people keep using them.  Your statement about why would Garrett come out with a new design is a good question. But the answer is simple. They had more demand from the gasoline performance world wanting bigger 3€ oulets to make it simpler to build exhaust systems.  Garrett didn€™t change it to increase spool or performance.  Yes, Garrett really pushes their new GT turbos as better spooling but this is because of change to Ball Bearings, not a change in the housings.

You definitely had a kit that wasn€™t correct. And like other people we would have taken care of you had you called us. I am sure you understand that, and I too understand that sometimes you just can€™t wait. You€™re in the middle of the project and something happens, and you just deal with it.  Especially on the weekend, this is not something that can get fixed and it can be frustrating.

Regarding some of your CONs of the PERRIN kit.
We will never use a bellows anywhere on the kit.  This is because they do not hold up to the temps and pressures seen before the turbo, or at the WG dump tube. We looked to using these a long time ago, and no one would guarantee theirs would hold up under 1600 degrees+ and deal with the pressure.  Using one after the WG dump is an ok place, but it is not needed as the catbacks contain the flex.

The filter is a tuff one.  If you understand how they work, there is no reason to have K&N on your mind.  If it is a looks thing, well we are changing something there.

The oil drain is pretty simple, a flange, fitting, and hose connecting it to your OEM drain.  Getting it nice and smooth is easy.  This is not something we have had issues with.

Flanges welded to the outside. This is something we well also not change.  Welds on the inside of the pipe or butted up to them, do not have very good support.  The tubes will have better support if fit tightly to the ID of the flange, then welded on the outside.  Welding on both sides is really bad with Stainless steel.  This is because SS shrinks when you weld it, and it can cause stress on the weld when welded on both sides.

Regards to no BOV. I know where they got this info.  At SEMA a couple years back Precision turbo was next to us and it came up in conversation. I thought they were nuts, but whatever.  I asked Garrett about this, and while their new turbo can take 10 times the force of the journal bearings, but that doesn€™t mean you shouldn€™t use a BOV.  Also they have as part of their warranty questions are they using a BOV or a functioning BOV.

Now a couple of situations come up when a BOV is not necessary.  A race car that does 99% of its shifting with flat foot shifting. In this situation, the throttle never closes during shifting, so there is no need for a BOV.  The other situation is low boost.  Say up to 5 or so PSI, a BOV is not that necessary. At this point the 5psi of back pressure trying to stop the turbo (during shifts) isn€™t that bad for the turbo. And generally an engine/turbo running 5psi is pretty responsive so re-spool isn€™t a problem.

But you still want to use one in any Subaru application. They run too much boost, and if you want your turbo to last as long as possible us a BOV.  While not running a BOV may be OK on a turbo, its not good for respool. That sound is the air backing up in the boost tube going through the turbo. At the same time, your turbo is either stopping or really really slowing down.  Also this rush of air going backwards through the system will cause bad MAF readings and poor drivability at low speeds.

Using Crawford as an example may not be the best as all of their shop cars are race cars. They don€™t even need a throttle plate!  But it is very interesting that they have gotten good life from their turbos.


 Posted by on August 17, 2007 Forum Posts, Part Design & Tech, Turbocharger Testing Tagged with: , , , , ,
Aug 172007

First let’s start with the car. I am not going to get into the stats of the car in stock form.  Its by no means is it the fastest car, or the highest G load car, but it does everything pretty well, especially handling and feel.  I have owned it for almost 2 years now and has been up for sale 2 times, but never sold.  Mainly because I didn’t really want to get rid of it!  Well I decided to sell to the STI as the new model was coming out, and there wasn’t much let to modify on it.

So I started looking at the little red car in the garage.  Over the years, my wife mainly drove it, and I put up with some of the little things I didn’t like.  There was really only 2 things I didn’t like, the power or lack of power, and the placement of the pedals.

I am big guy, 6’4″ and way more than 200lbs. So this little car isn’t something that really fits my physic.  When I was falling in love with the car, the only concern I had was can I fit.  Believe it or not, there is plenty of head room for me. Leg room…..  well its not perfect.  But most cars I have owned (except the Mini) don’t quite have enough leg room.  Over the next few months, I started to tweak the pedals, closer to the floor to allow for more room. Well after some simple adjustments, it was nearly perfect!  Nearly, as the clutch pedal wasn’t really adjustable.  I saw a way to adjust it, but I had to remove the clutch master cylinder and space it from the foot well. Sounds easy on a normal car, but on the Elise, it’s a little tricky.  The only way to get to it was to remove the front clamshell.

One thing I really found I love is how simple yet technical the car is.  Things like the body panels, suspension, chassis, are so simple in their construction, but at the same time they are very technical in the way they are made and designed to work together.  While removing the front clam might be easy and the clutch is something I want to adjust, I have Horsepower on the brain!

Like I said, it’s a fast car, but it could use another 50-100HP, and it would be perfect.  So, how to get 50-100HP??  There are supercharger kits and turbo kits available for the lotus, so which method??  Supercharger kits never really get me excited as they are expensive parts by them selves compared to turbos ($3000 vs. $1000) and they cost you HP to drive them.  A SC kit requires a lot of off the shelf parts, where a turbo kit requires more custom parts, all of which are things I can build myself.  Some argue a SC is more responsive, as they build instant boost.  For a light car like this, a SC would be a very good, but expensive option.  But, comparing an engine running the same boost, the turbo (when sized properly) can be just as responsive, and make more HP than a supercharger.  While the high compression engine is controlling the limit on HP, it also helps to make a turbo spool up quicker.  In the end, the right size turbo will build more boost at lower RPM than the SC, and it will not have the 20-30HP of drag on the engine.  I think the obvious choice is the turbo.

Like I am going to buy someone else’s kit, when I can make it myself!


With my experience with turbos, and a few calculations of engine air flow at different boost levels and RPM, I mapped out a few Garrett compressor maps.  There are about 3 turbos, or basic turbo sizes that I had a feeling would work well.  The GT2554R seemed like a good turbo, as does the GT2560R, and GT2860R.  The GT25 turbos will spool instantly, but the high reving, and high compression motor, needs to breathe!  Both the GT25 turbos have a very small turbine wheel, and while these will make the power I want, they could cause high exhaust back pressure and cause an increase in EGT’s.   The GT2860R turbo might be a little laggy compared to the other smaller ones, it should still be responsive enough to build boost before 3500RPM.  When the turbo will spool up is kind of a mystery until we can fire up the engine.  Because I rarely drive the car below 3500RPM, the GT2860R is the turbo of choice, or is it??  There is another turbo Garrett makes that is very similar to the GT2860R, that is the GT2860RS (Disco Potato).  The RS is rated for an extra 60HP, and is known by many to not be much less laggy than the R model, but make more power.  The difference in the turbos is the trims of the compressor wheel and turbine wheel. The larger trims make the turbo flow more air, and be freer flowing.  We just happen to have one of these sitting around the shop!  Along with a few others:tech_turbo_2lgt2554r_471171_3_comp_e





In reading about the turboed Elises out there, I see that some people have boost creep problems.  All the turbo kits use internal wastegates with small ports for bleeding off exhaust pressure, which could be part of the boost creeping problems.  So an external wastegate became part of the turbo kit equation.  External Wastegates have very large ports to bleed off exhaust pressure, plus they look way cooler when installed!  These are also parts we have sitting around the shop.

Engine Managment

In order to run the engine with the turbo kit, good engine management would be necessary.  Again, reading about the other Elise turbo kits out there they all use crappy EM to run the car.  Piggybacks, reflashes, all of which rely on someone else’s tune. Not to mention are known for blowing up a few engines.  This just doesn’t cut it for me.  So I turned to Hydra EMS, who I have used for 3 other project cars. They offer stand alone, plug and play ECUs for many cars one of which is the lotus.


The HYDRA has to be installed in the trunk. This requires re-pining the harness, drilling a hole and running a vacuum hose.  Not a big deal, just takes some time.  Before I go installing the turbo kit, I installed the Hydra and got it running in NA mode.  Tuning the Hydra is simple, and I bought the integral Wide band 02 sensor with it that allows logging to include the wide band and the auto tuning feature to work.  While the wide band 02 sensor allows for the auto fuel tuning feature to work, its not good enough to get the car fully tuned.  But it helps to get you close.



With any turbo system a good large diameter exhaust is needed.  Before the turbo kit goes in, I built a 3″ single muffler exhaust system.  While a bit loud and large for the NA engine, the 3″ exhaust, it would soon show its worth, when the turbo kit is all done.  I used 3″ 304SS tubing, and a straight through 3″ round muffler.  I had an old High flow metallic cat lying around which I also used to not only be emissions friendly, but to keep the sound somewhat in check.  This header back exhaust design utilized the OEM flange with donut gasket, so it could bolt to the factory header.  While this flange was a temporary until the turbo kit was done, it would serve as a good starting point for the turbos’ exhaust system.


So I have the turbo, wastegate, tubing and the other basic components to start building the turbo kit.  Now its time to pull the back of the car off to plan where its all going to go.

I looked everywhere on the net for some how-too’s on removal of rear clam. They just don’t exist. So no big deal, just means I will have more fun doing it. First step is removing the battery, battery harness, and tail light harness from the trunk. Once this is done, there are 4 screws that have to be removed that hold the rear clam to the chassis.  Since I built a rear panel eliminator, there are only 3 other screws that have to be removed from inside the trunk.

From there the quick and basic steps are:

Remove the wheel well liners, remove the bolts holding the body to the rear diffuser, remove the seats, remove the plastic rear speaker shroud (careful of the speaker wires, and the proximity sensor, remove the 4 nuts holding the trunk lid pivots, remove trunk lid, remove the upper roll bar cover, remove screws holding body to roll bar, remove plastic roof latches from body/roll bar, remove 2 bolts on each side of body where the upper clam meets the lower body (2) on each side,  Removing all the obvious bolts and screws are easy, but there are 2 hidden screws that are not easy to find.  These are located behind the seat belt tensioners toward the outside of the car.  All of these bolts are 10mm head bolts with large SS fender washers behind them. With the back of the car removed, I can now start figuring out where the turbo can go.


With the back of the car remove, the car looks kind of cool!  Maybe i will leave it like that…..



Now being realistic!

While its no fun my wife had to go on a trip to China, and my step son vacationed at my dads house, it gave me 2 weeks to finish the turbo kit up!  I already have the Hydra installed and running, so when I get the turbo kit done I can fire it up right away!

With the exhaust system built, Hydra installed, and rear of car removed, it was time to start planning where the turbo will go. I decided on using the GT2860RS with an external Wastegate. This turbo is very small and compact, and will be very easy to fit behind the engine.  I purchased a ½” thick Laser cut flange for the head to start with, and bolted it to the engine. From there I used

I had to reinstall the rear body a few times to make sure things cleared body and chassis parts. Once I got the turbo sittin’ pretty, I built a little jig, by welding some 1/2″ SS rod to the header flange and turbo flange.  This allowed me to remove the “Header” from the car and start putting together the primaries.

Choosing the primary size was easy as the flange ports were 1.5″, and this would be plenty big enough for the HP I would be running.  To ensure it would hold up for a long time, I made sure it was .125″ wall.  This thickness ensures that vibration, and the weight of the turbo will have little effect on the durability.  This thicker material is also good at heat retention       so once heated up it will help keep exhaust velocity up.

With the jig off the car, and few days of working after work, I had the header completed.





To keep the part looking good, and to add some function I decided to ceramic coat it.  I had used some VHT header coating in the past with great success, so I decided to use it once more.  This coating is $8 a can and one can, will do the trick. The only important thing is the header has to be scuffed up a little to ensure the coating adheres to it properly.


With the header nice and roughed up, it was time to coat it. The coating turned out great!  The trick is to make sure you do a lot of light coats, while not going too thick, as this can cause it to crack after the initial heating process. I used the black colored coating as it is a very clean look. It was pretty barried in the engine bay, so I could care less about it being all shiny and polished.




Upon completion of the header, I noticed the flange was not so flat anymore.  I tried to make sure to not use too much heat while welding it together, but SS really likes to move when welded.  To ensure it was not going to be a problem, I had it ground flat.  Of course I didn’t notice it until AFTER I coated the header, hence the black header with a shiny header flange.


While I was in the mood for painting things I decided to paint the compressor housing of the turbo.  Again, turning to VHT for some more paint, I ended up buying a couple cans of wrinkle black and wrinkle red paint. This stuff is also awesome paint.  I have used this on the H6 project, and on a couple other random things.




With the turbo mounted, it was time to adapt my exhaust to it.  Toyota was nice and used a bracket to help support the OEM header, and I decided to utilize that to help support the turbo.  It worked out perfect to build a bracket onto the flange for the turbine outlet. Next was getting from this flange to the exhaust I already created.  Since I have to cut of the OEM donut flange off the exhaust, I had to replace this with a flex joint. From there it was easy, a V-band flange, some bends, and polish it all up, weld it together, and bam!




With the Exhaust system short, free flowing, and polished up, it was time to think about the External Wastegate, and how it would fit into the equation.  Like other parts of the build I wanted it to look good, and be functional.  Why not put it behind the turbo at the back of the car where it might be seen. Plumbing the WG dump tube back into the exhaust was something I really wanted to do, but upon inspection, things were just too tight.  It had to be plumbed into the exhaust before the flex joint, and there was just not enough room to do that.  So I vented it to the atmosphere. Normally I would shy away from this as it can be very loud, but who knows, running 5-10psi of boost may not make much noise anyway.  Using the hole in the rear diffuser where the OEM tips came out sound like a good idea.build_lotus_externalwg




Now that the turbo is setup to breathe, its time to build boost tubes, and the intake system. Starting at the turbo, the intake was first. This was pretty simple, a PERRIN air filter stuck to the turbo inlet, done.  Yes this isn’t normally the best place to put an intake, but on the lotus engine, there is no extreme heat it would be seeing. The block is right in front of it, but also is the suspension and lots of ambient air flow.  Routing the boost tubes to the intercooler is going to be tight, but doable. Before I get that far i have to design the intercooler, and decide where it can go.

The first thought was to use one of the side scoops for the fresh air to it.  Looking at many of the other turbo kits out there they too use these scoops. The only problem is none of the are very large, and none of them are in a very good place. They also have to use helper fans to make up for their small size or poorly mounted location.  There is no way that helper fans are going on my car!


I used the drivers side scoop and started to lay out where the IC can fit.  I ended up using part of a Legacy GT intercooler we had sitting around. Using what little space there is in the scoop area, I ended up basically resting the IC on the fender liner.

Now that the core has a nice place to sit, time for end tanks. I started with some 4″ tubing and cut it in half to create the end tanks. From there, I cut some caps out for the end and welded an inlet tube and an outlet tube. To ensure it got good ambient flow from the scoop, I built a shroud around the intercooler to direct the air through the core.  Other intercooler setups I have seen just let the ambient air flow around it. This is not good.


With the shroud all welded to it, I wanted the intercooler to look like it was supposed to be there, so like other parts, I painted it.  This time I used the black wrinkle finish.  As you can see from the pics, it looks OEM.



With the intercooler in place, building the boost tubes was easy.  With a few bends here and there, a MAF sensor, flange, some time on the polishing wheel, and now then engine can finally get some boost.

I can’t forget the blow off valve!  This was an easy choice, I used my trusty PERRIN signature series BOV #000. Its been used on my last 3 cars, and still working great!  Instead of the normal silicone coupler and a couple of hose clamps, I used one of our universal adapters, and welded it to the boost tube. This allowed me to screw the BOV to the boost tube.


With the main parts installed and nearly ready to fire, it was time to give the turbo its vitals, oil and coolant.  Getting coolant was easy, I just used the coolant input on the overflow tank, and ran it to the turbo, and back to the tank.  This provided great flow, and reasonably cool temps for the turbo. The oil feed was a little tricky. No one really shows a good picture online of how they hook up. The backup plan was to unscrew the oil pressure sender and tee into that. Upon further inspection, my car has the dual oil coolers and a nice sandwich plate.  Bingo, perfect fitting at the 12 O’clock position!   The sandwich plate has a bleed fitting to help get oil out of oil coolers during an oil change. I just used some -3 SS Teflon hose, and some speed fittings. These allowed me to custom make the hose in the shop and not have to go down to a hydraulic fitting store.

Once the turbo gets oil it has to get rid of it. Again the simple solution is tapping into the oil pan. Once removed, I welded a small SS tube into the side, and reinstalled it. Now that makes it sound easy, but I spent about an 2 hours on this part alone.  5 minutes to weld cut the drain, and rest of the time getting the dump pan off!  The OEM use of RTV is nuts!  I am not even sure why there are bolts holding it on!

To ensure all the oil and coolant lines never had a problem with melting, I used quite a bit of our PERRIN Pyroshield to cover everything.  This cover is good to 2000 degrees, and keeps the internal hose under its melting point. This ensures that there will be no issues with hoses melting or blowing off.




Because I like to build things myself and not buy other peoples parts, i wasn’t sure what I wanted to do about the injectors. I could buy some, or I could try modding them.  We learned this little trick with the Subaru injectors, where you can remove the small screen on the end of the injector and get them to flow more fuel.  The problem is we have never done this with the Toyota injectors, so how much will they flow????   First off they are a Denso part just like the 2002-2005 WRX injectors. In theory, if they use the same basic injector, and just change the screen to flow different rate, these should flow about 800cc/min.  So after carefully modding them, sure enough they have the same ID where the pistons lifts from, and they have the same lift!  PERFECT, I don’t have to go buy injectors that may not fit or may not plug into the injectors.

Along with the injectors, i got a set of Brisk Spark plugs. While most people have never heard of them, they make a really nice part. The set i used are the silver racing eletrode plugs. These are a better plug than the iridium for power, but  not quite as long wearing. But who needs plugs that last 100K miles!  This item is something you will see us selling very soon!


Well after a year of driving and a year of somewhat hard driving the rear tires are toast!  Stock the tires are 175 fronts, and 225 rears.  While this is a small light car, and those sizes will suffice…… who want to suffice!!  Again back to the forums for some insight as to what can fit.  195s on the front and 235s on the back are common upgraded widths, but can that be pushed???  So 215s on the front and 255’s on the back were just going to work!   Now to pick the tires!  The ultimate street tires in my mind are the Yoko A048s. But they are expensive, and don’t last long, but grip like crazy when warmed up.  John Lietl over heard me thinking of new wheels and tires and said, “hey, you help me build my Evo turbo kit, then I’ll give you my A048’s”.  I had to ask to make sure he hadn’t gone out for beer at lunch but sure enough, he had a set at home, and an EVO turbo kit was on the PERRIN-Evo-parts-to-build-soon list. We have a deal!

Wheels while easy to pick out, are very hard to find the right offset.  Custom ones can be made, but in the end there were 2 pretty good choices I found that fit.  The Team dynamics pro race, and the PIAA FR-7, look great come in the right sizes.  I went with the TEAM Dynamics wheels as their price, and availability was perfect!   Semi gloss black 17×7’s and  17×8’s replaced the 16×6 front, and the 17×8 rear.  I think the biggest change is in the front wheels and tires.  The OEM fronts look like front wheels from a street bike compared to the new ones!  This side by side comparison shows the change in contact patch.


After many clamshell installs, and test fittings, cutting, trimming, welding, trimming again, and polishing, it was all done, time to fire it up!  Since I had no map for the injectors, I had to build it. The Hydra has a really nice injector change trim feature which allows you to enter the stock inejectors, and the upgraded injectors, and it recreates the base map for you. I tried this out and removed some timing, just to be safe.  I hit the start button, and it fired right up the first time and ran great!  AFR’s were in check and it was time to let it do a few heat cycles to ensure coolant hoses and oil lines were all good. No leaks!!



The nice thing with high compression engines and turbo kits, is that they don’t loose power anywhere compared to the stock engine. Sure enough the car finally has some low end power!  With 5psi of boost, and some initial tuning, I was well on my way to getting the car tuned to 10psi!


Next to come is a Prototype PERRIN PWI-2 Water injection system, and dyno results!


Shout outs:


Hydra EMS

Team dynamics



Elisetalk forums

My Tig Torch

My wife

oh, ya PERRIN Performance!


Test and Tune Session…..Finally

I finally got around to putting up the dyno plots from the tuning session.  While i had been doing alot of road tuning before the dyno session, there was quite a bit of power left on tap.  This is why a dyno tune is important.  AFR Targets and watching for knock only get you so far. Having a great tool like the dyno shows where a specific AFR at a specific RPM makes more power. It also shows where different cam advance numbers make more power, which is not something you can see with datalogging.  While dyno tuning is not something that anyone can just go get done, on any turbo setup, i think it is very important to do.

So i know there are a lot of guys with Turbo, and SC packages, but it seems lately the buzz is all about Superchargers.  I am a big turbo fan, and i think that turbo is the way to go.  With a turbo setup, you get more boost down low, so more torque, and you don’t get the HP losses from the SC.  Overall a Turbo is more complicated to install, more parts and more expensive, but it is well worth difference!

Full Write Up on the car is located HERE

After a few weeks of road tuning(driving back and forth to work) i still hadn’t been able to determine where to turn the lift on.  I started at 5800 which is where alot of the tuned ECUs put it. This seemed ok, but not real smooth when it kicks on. I am sure many of you are thinking, did you tune it during the changes? Yes!  Of course. When tuning a car, you can just change one thing and expect results. There are many things to tune on the car to ensure that the changes you make are not waste.  I spent quite a bit of time tuning the car at 5800 RPM point of lift engagement.  3 things occured.  No matter what i did, a loss in power, and a rich condition.  Lastly the boost dropped quite a bit.  After leaning out this transition, adding timing, and even some cam timing changes, it never felt as good as stock.

For this setup, i am using the Hydra EMS plug and play ECU. This is a great tool for tuning cars, as the changes are instant, no flashing, its as simple as reading the maps, and the wide band, and making changes. Also it has great knock sensing capabilities, and feedback, so you can see where the engine is starting to get noisy.

Then i did some reaseach about the SC cars, and found that they turn the lift point on at 4500. So i did the same thing, testing this cam change over point, resulted in major low end power loss. Same thing, lots of fuel, timing, and cam timing changes, and it never was that good.  So with that said it was time for the dyno.


These are the first runs with the lift at 4500. As you can see, just like i felt on the road, a large loss in power.  Not to mention the huge drop in boost when it kicks on. The strange thing is, the Blow off valve actually blows off a little when this happens!  I experienced this same thing when tuning another project car of mine, the Subaru H6 project. The H6 Subaru engine would drop about 3psi when the lift kicked on (when turned on below 4000) and it caused a 100HP and 100ft-lbs loss in power!  Only the lift was turned on before 4500, it was fine. Same thing here.


After experimenting with the lift at a lower boost setting, the graphs finally started to smooth out. The Dyno we use is a Dynapack, and is very sensitive, which is why the “jitters” show up on this. We can see a 1 degree of timing change on this dyno, so its great for R&D, but not the best for producing Dynograph to brag from. It was time to turn up the boost.


So why didn’t the 4500 lift point work? Well on the SC cars, the SC is flowing a linear amount of air through the RPM range.  So when the lift kicks on the SC doens’t loose boost from different engine air flow  from the differnet cam profiles.  So the transition is much better.   Some of the reallly big turbo kit guys in the celica forums turn the boost on lower, but they also are using huge turbos that dont build boost until after that point.  Anyway, that is my guess.


So after all that, i ended up with the power i was looking for 260WHP!  The torque i didn’t really have a goal. I knew i wasn’t gonig to run too much more boost than 8psi, so the torque would be kind of limited. Still 190 ft-lbs, that is plenty to move this 2000 lbs car!


You can see the boost curve i started with and ended with.  The more boost we ran the more the lift caused a drop in boost in boost.  You can see how the high cam effects boost.  The lower valve overlap at lower RPMS helps keep boost in the engine.  The high overlap shows how when the lift kicks on that boost is getting blown out the exhaust.

So after all that, what you see is what i got!

The one thing that i wish i had done previous to building the turbo kit was do a baseline of the bone stock car. This just didnt happen, so all i can do is guess at the Wheel HP i had previously.  Best  guess i somewhere in the 160-170WHP range and somewhere around 110-120ft-lbs.

So i think most people want an Extra 100HP from there Elise, which gets it close to the HP per pound ratio of Vettes and Ferrari’s.  This is using CALCULATED WHEEL HP versus pounds.

PERRIN Turbo Lotus 7.6 pounds per WHP

C6 Vette 8.8 pounds per WHP

997TT 7.7 pounds per WHP

ZO6 Vette 6.5 pounds per WHP

Just something to think about when comparing this to other super cars.

After all this buildup, and dyno tuning, its time to sell the car.  Not sure of a price, but i am thinking somewhere around $40,000. Seems fair?? Not sure, but i have had the car 2 years, and its time for something new!

I would be happy to share anything about the build, or anything about the tuning of car.  We never made any parts for the Elise, so i am not here to compete with anyone, just sharing fun info!





 Posted by on August 17, 2007 Dyno Test & Tune, Project Builds Tagged with: , , , , ,
May 242007

Described in this article are 3 very popular Subaru applications for the PERRIN PWI-1 water/methonal Injection system. We will be talking about the benefits of Water/Methonal injection, and proving how they work. The Features of the PERRIN PWI-1 system are best found in the features tab. Things in this article are specifically about Subaru€™s but the same types of results can be had with similar applications.

Firsts lets talk about the term Water Injection. This is somewhat a generic term referring to injecting a water/methanol mixture into the engine.  The mixture of water to methanol can vary to create different results.  Water is used for in cylinder cooling and Methanol is used for its high octane rating, and its ability to remove heat.  Water doesn€™t burn but sucks up lots of heat from the combustion chamber. Injecting this by itself will cause a loss in power if the ECU is not retuned for it.  Methanol does burn, and has a very high octane rating. The in cylinder cooling from water, and the high octane from Methanol create a mixture that will significantly reduce the onset of detonation.

Water/Methanol injection is something tuners are looking for as this doesn€™t limit them to boost level had by low octane pump fuels.  For all of our tests we use a 50/50 mixture. This is a safe mixture, and provides the biggest benefit of cooling and detonation control.

How can tuners use water/methanol injection to increase power? That is simple!  With the reduction of detonation/knock, a tuner can increase boost pressure, increase ignition timing, and lean out the fuel mixture.  All things that may not have been possible with standard octane pump fuel.

The Tool

With all of these tests we are showing off the PERRIN PWI-1 meth/water injection system.  There are many features to this system, and probably the most important is the failsafes we have built into them. With the PWI-1, we use a flow sensors to map out the flow of water vs, injector duty cycle.  With these 2 bits of info we can see if a nozzle is block or a hose poped off.  The brain also has the ability to adjust the amount of flow it should be seeing based on different nozzle sizes.


Much of this info can be found on our site where you can buy the PWI-1 System. CLICK HERE

The PWI-1 failsafe is hooked to a relay. This relay give yous the freedom to hook it up a bunch of different ways. You can use it to change maps in an ECU, cut power to a boost solenoid to lower boost, power a light to indicate low flow, or any number of things.  This is what makes our Water injection system stand out from the rest.  This, along with its progressive nature in delivering more water/meth with more fuel flow, creates a perfect water/methanol system!

Case Study#1

This first example of how water injection can be used is shown on a very common setup.  A 2005 Subaru WRX 2.0L, with stock turbo, stock Top Mounted intercooler, and catted turboback exhaust. This is also known as a common Stage 2 WRX.  This car was first tuned on 92 octane pump fuel.  As PDXtuning pushed the limits of the pump fuel they settled on 17psi of boost, and a safe air fuel ratio of 11.0-1.  This netted 224WHP and 238ft-lbs of torque. Any more boost, or any leaner mixture and detonation started to happen.

Initially turning on the water injection with the existing tune actually looses a little bit of power. This is to be expected as you are injecting water (which doesn€™t burn) and methanol, which further richens the air fuel mixture. Water injection allows a much leaner Air Fuel Ratio.  PDXtuning started to lean the mixture out to 11.5-11.7AFR. Great power gains, were see with this alone. Next is boost, with the limits of the turbo size, PDX increased boost about 1.4psi more to 18psi.  Along with this a couple degrees of timing were added across the board, and below are the results.


One thing to notice is how much smoother the runs with the water injection are. The Dynapack dyno is very sensitive to things like detonation, and timing changes, which in turn shows up in the graphs.  The smoothness shows detonation is far from happening.  The PWI-1 system on this car is a very potent tool that proved its worthiness for this customer and tuner.  The PWI-1 was a huge part of making this stage2 WRX arguably the highest WHP Stage 2 WRX out there!

Case Study #2

This second example of how water injection can be used is on another very common setup.  A 2006 Subaru STI 2.5L, with stock turbo, stock Top Mounted intercooler, and catted turboback exhaust.  This is also known as a common Stage 2 STI.  This car was first tuned on 92 octane pump fuel.  The STI has one major thing that hinders its ultimate WHP output, the turbo!  Not matter what you do the most boost you can get at redline is about 14-15psi.  This limits the obtainable HP to be had at the upper RPM€™s.  But they can run lots more boots in the midrange.  With Stage 2 STI€™s, their big power and torque gains happen here, and this is where the PWI-1 will show its strengths.  PDXTuning settled on 17psi of peak boost, and a safe air fuel ratio of 11.5-1.  This netted 20WHP and 20ft-lbs of torque over the base supplied map. Any more boost, more timing, or any leaner mixture and detonation started to happen.

dyno_methinjection_aaronbasetune copy
This graph shows a base map ran on the dyno, compared to a tuned map from PDXTuning.

The run above shows the tuned map with nothing else but the WI being turned on.  Like in the above car, turning on the water injection with the existing tune gains no power.  A loss in HP, is pretty normal with any water injection setup and to gain power back you need to lean the AFR€™s back to where they were.  In this case PDXtuning started to lean the mixture out to 11.7-11.9AFR€™s and huge gains were seen.  This time boost would be left alone, and timing would be increased.  The 50/50 mixture allowed for some crazy timing increases.  The timing numbers ended up being about 3-5 degrees higher!  More timing equals more torque and power!

dyno_methinjection_aaronwateronfuel copy
Shows great gains with same amount of boost. That is safe big power!

Next up is boost.  With the water injection turned on, the engine loved more boost.  With in reason the boost was turned up as much as possible, which at peak power, and redline was not much different than the first runs. Again, this was due to the size of the turbo, and is why peak power at redline isn€™t uch different.  PDXtuning increased boost to about 20PSI at peak torque and as much as possible at redline.  With the added timing, boost, and leaner AFR€™s, the upper RPM increases were not huge, but check out the Torque!  Like the other car, this Stage 2 STI is the highest torque PDXTuning has ever seen!  That is V8 torque from a 4 cylinder!

This graphs shows it all, more boost, more timing, less fuel, water injection on, and big power gains! This graph compares base tune map with no water injection on.

Case Study #3

This case is brought to you buy HARMON MOTIVE.  Another great tuner in the Subaru World shows off their ability to tune, and use a PWI-1 system on a 20G powered 2006 ST0 on 91octane California fuel.
On this 2006 STI, our customer wanted to make a lot of power on his daily driver while maintaining a very stock appearance. The Perrin WI kit was the perfect addition to this setup because it allowed us to make great power while retaining the stock top-mount intercooler.


20G_18psi_91oct.drf  BLUE RUNS

Running on straight California 91 octane pump gas, we tuned the car to a peak boost of 18psi falling to 17psi by redline. Air fuel ratio was kept at a conservative 10.8:1 to help reduce the chance of detonation with the low quality fuel we have. Once we achieved a consistent and stable tune, we moved to the water injection.

20G_20psi_WI.drf  RED RUNS

Since we had reached the limits of safe power on 91 octane, we started to tune using 100% water. With the water injection turning on at around 7psi and using a .8 nozzle, we first leaned the car to 12:1 air fuel ratio. With the leaner mixture, power was already starting to increase. Now that we had the optimum air fuel ratio, we added 2 psi of boost and a couple of degrees of timing to achieve 20 additional HP and 25 lb/ft of torque.

20G_22psi_Meth.drf GREEN RUNS

To get that last bit of horsepower and torque, we changed the mixture to 50% water and 50% methanol. The methanol has a dramatic effect on octane levels and allows us to run more boost and timing over water alone. We were able to add another 2 psi of boost (now 4psi total over pump gas) which allowed us to make an amazing 377 lb/ft of torque to the wheels. Horsepower was also increased to 353whp.  We were now making 30whp and 47lb/ft over pump gas! Best of all, with the 3 gallon tank we used, the water and methanol need to be refilled only once every couple of weeks!

Thanks to Dan, Paul, and Ian for the awesome write up and install of the PERRIN PWI-1.

From these 3 tests you can see how water injection is a great way to make safe power. Especially for customers with 91 octane, which is normally very limiting, this is like running race fuel in your car all the time!  Look for most Water injection tests to follow on Diesel trucks and some SC V8’s!


 Posted by on May 24, 2007 Dyno Test & Tune Tagged with: , , ,
Jan 172007

Keep in mind that this project was just for fun, this isn’t a kit that we have ever sold. While we do have a few parts that work, we have nothing specific we can sell to help you with your own H6 project.

This is kind of long, so sorry ahead of time. You can just skip to the bottom see the dyno graphs, but that would be no fun.

Summer of 2005, SEMA was coming up soon, and what could we do that would wow people.  With ideas floating around about different cars to buy, build, or mod, we were kind of up in the air about what to do. Then the word H6 came up.



There are many things about this engine that are very cool. Just looking at the specs doesn’t do it justice.  3.0L, 6 cylinders, DOHC, AVCS, AVLS, 250HP in stock form, aluminum block, forged steel crank, chain driven cams, and only .700″ longer than an EJ20!  Did I mention 3 point zero liters!  Being familiar with the 4 bangers, the first thing that I was interested in seeing was how the Variable lift worked.  The cams are the first strange thing you see as each valve has 3 lobes. One central lobe for the low lift and 2 outer ones for high lift, longer duration. The bucket is where the magic happens. There is an inner and outer piston that rubs on both cam lobes all time. When the solenoid allows oil pressure to shoot through the oil gallery, it locks the inner piston to the outer piston/bucket, and bam, new cam profile.  I have to say this is probably the coolest part of the engine.  Word is this is a co-developed technology from Porsche and Subaru, sure enough the parts are made in Germany.


Cutaway of EZ30R, aka H6

After getting the engine in hand a few other things that surprised us.  The manifold is plastic, which sounds scary. But like other intake manifolds on cars, this is a glass-filled Nylon, which is good to 400+degrees and will hold high pressures at these temps. Plus the way these are manufactured, they allow for very smooth, very large internal diameters. Second surprise is the ports on the head. They are huge compared to the 4 cylinder ports.  I was a little worried as since each runner is feeding smaller pistons they might be smaller than the 4 cylinder ports which feed larger pistons. But we were wrong.  Another thing that we really liked was the throttle body. Yes its feeding a bigger engine, but it is feeding less power, so smaller throttle body??? Nope! Even better it was bigger!  3″OD vs. the WRX 2.75″.  Another good surprise.


Of course everyones worry once the heads came off, was the cylinder walls. They were a little smaller than the 2.5L walls and so were the iron sleeves cast into them. But would this matter was the question.  As far as cost and time goes, re-sleeving wasn’t really an option for this build.


This build was a test of the basics of the H6, so drop in pistons were the answer we were looking for.  With recent interest in Supertech products, we sent them an OEM piston set to build our first set of custom pistons. Because this was a SEMA car, Willy at Supertech, was very excited about doing the H6 build as it was nothing he had seen before. This was a huge help in getting our pistons right away and getting the ball rolling with the build.


As mentioned above, the first build was done to test the waters. There was no need to sleeve, and do other crazy things if the head bolts don’t hold, or the chain fails, the oil pump doesn’t pump enough, or who knows. Forged low compression pistons, were a great answer to proving the H6 or not.  Now that the Supertech pistons were being forged and machined, we could continue with planning the other things to complete the build.

Interest in the build was also seen by a few other close friends at PDX tuning, and another from a place where they talk funny, Minnesota.  Because these friends and myself were 100% on board with the build, we had Supertech build a couple more sets.  Everyone had their own idea with how they were going to build their motor, talk of sleeving, porting, valves, an monster turbos were making us rethink the decision of just pistons.  But we needed to stay focused to ensure we got done before SEMA.  With the engines apart and ready for some new pistons, the builds began.

Because there wasn’t any aftermarket parts for this engine we turned to Subaru for many things.  Factory head gaskets, piston rings, head studs and other gaskets were used to reassemble the engine. The cases were not split, so factory rods remained in place, as did bearings, and we trusted the OEM clearances were good to go.

Time to drop the pistons in!  Just like they should, they had the right clearance we speced out, and they fit great. During the installation, we came across another thing that differs from the 4 cylinder. The wrist pin installation is just a little trickier.  In order to get to that center cylinder and its wrist pin took some patience, and custom tool. But once we got the hang of it, no big deal.  The wrist pins fit the pistons and rods perfect, so it was time for the next step.

Of course in building an engine like this, there are many new things that come up.  Because of our experience with the 4cylinders, there isn’t really any need to reference the manual except to double check the head torque sequence and a quick glance here and there.  But with the H6 forget it, you need the manual nearly the whole way.  There are about 100 times more bolts and more important torque sequences to deal with.

The first one is the head. The sequence is not what you think it would be (inside out) and the torque applied to the bolts was much less than the 4 cylinders. But like we said before, we would keeping this simple and doing one test at a time. So follow the manual it was.

An obvious difference in the H6 compared to the 4 cylinder is the front cover, and what lies behind it.  Subaru designed this engine to be as short as possible, and to do that they used chains to drive the cams instead of belts. It’s a little scary at first, but thank goodness for the manual.  But after all said and done, its just like the 4 cylinder where marks point in certain directions, and marks on the chain and gears make it very simple to install.  Then the front cover goes on with about 100 bolts.  The other difference is there is no real oil pan per say. The pan, is a major structural part of the engine, which has the studs for the tranny, adds rigidity to the two halves of the block, has oil and coolant passages and contains the baffles for the oil.  Oh and it is an oil pan also.

So in the end, everything was set, pistons fit perfect, had the right clearances, (thank god for Supertech doing their job) there was not a single thing that went wrong with the build, that we knew of……………….


What would .5 extra liters of displacement get us?  Better spool?  More power?  These questions all lead to one thing, the TURBO!  This was an easy choice.  We would use the most commonly seen GTXXXXR name thrown around the boards, the GT3582R. All people considering a rotated turbo always fight the decision between the GT3076R or the GT3582R. The downfall to the GT3582R is lag, and what helps with getting rid of lag? More displacement! This would the turbo to use, and show off what a 3.0L can do.  Plus this turbo I already had sitting on the bench, and it would flow enough air to make 500 WHP easily.

To bolt this turbo to the engine, we would use an off the shelf PERRIN kit.  In order to make an off the shelf PERRIN rotated kit fit, it would all come down to the header.  To start, we made a fixture to locate where the OEM uppipe inlet flange resided on a 4 cylinder. Transferred this fixture to the 6 cylinder, and we had our starting and ending points.

So what kind of header, equal length, how long, where should they collect?  Again sticking with a keep it simple but functional attitude, we made the header like the OEM header.  From the head, the 3 exhaust ports collected about 8″ down the tube. From here a properly sized tube was chosen to join one side of the engine to the other. Then each side collected and mated to the uppipe flange fixture we made.  The header was perfectly functional, but it had definite room for improvement, but we would have more time after SEMA was over. Header done, check!


Overall shot of version 1.0 header.  Very simple but functional header, that proved its worth.


Passenger side of header showing quick, short collector, and OEM uppipe connection.



Drivers side header.  The use of Tial V-band flanges worked great and we would definatley be using these for the future header.



Another thing that had to be designed was the engine wire harness.  Most people would just run away screaming like a girl but this when the fun started!  There nothing like taking a 2 month old 06 STI and cutting factory wires!  The 2.5L engine harness was used as a starting point.  Both the H6 harness and the STI harness were torn apart and laid out over the engine. Then began the cutting and splicing, soldering, and stripping of the electrical tape.  I wanted to make sure the engine was as OEM looking as possible that meant using the OEM plugs as much as possible.  After the harness was laid out and all soldered up, a fresh layer of electrical tape and wire loom was wrapped all over it. Looks like it came from the factory that way!  That is what I like!

The chassis electrical system was simple. It was simple for a couple of reasons. One, there was 2 more cylinders, so 4 extra wires, and coils and injectors were taken care of. Then a couple wires for the lift solenoids, and we are good to go. But what would plug into the factory harness, and run the car??  That answer was easy. HYDRA!  Andrew at Hydra EMS USA was ready and willing to write the special code needed for the different crank trigger and cam triggers. He was especially excited as there was a well known ECU manufacturer, that at the time, couldn’t get an H6 running. So there was motivation there.  The ECU was an off the shelf 05 STI unit with the plug and play harness, and a flying lead for the 6 new wires.  Electrical done!


Next is oil and coolant for the turbo. Where do we get these as there was no stock turbo on this engine.  Oil was easy to get as the AVLS solenoid block was right next to the turbo.  We will just tap into one of the plugs and get pressure there. Getting rid of the oil from the turbo was a simple dump tube draining into the oil pan. There were coolant passages all over the engine, it was just trying to figure out which one to barrow for the turbo coolant input and output.  After some digging through the factory service manuals, to check coolant flow, we had our lines to tap into. Some tees, and unions, and turbo had it vitals and it was ready for firing.


The fueling was something we were a little worried about, as the stock H6 injectors were way too small, and they were not easily modifiable.  But luckily some good-ole blue WRX injectors fit perfectly. And they are easily moded. The moded WRX injectors flowed roughly 800cc’s and they would be good for 750-800 engine HP on pump fuel. Next is the fuel pump. The obvious easy choice is the Walbro 255LPH pump. It would support 500WHP easily, and it is a tried and true fuel pump. This defiantly wouldn’t work for going too far beyond 500,but it would be the perfect answer for this time around.

Like all other Subaru fuel rails/systems, the H6 rails, were not going to cut it.  First off the rails are NOT a traditional returning type of fuel rail.  The rail is also NOT a return less system, its something in between. There is no “fuel flowing” through the rails. The regulator is located right where the feed enters the rails, so the fuel never flows through the rails and out the end.  I experimented with this partial return less system on an FP Red and it worked.  But for this build, the less experimenting the better.

Like the other PERRIN high flow rails, these were going to be setup equal length.  Plumbing in some large .375″ID hose to the end of the rails would easily supply enough fuel. The stock STI fuel pressure regulator would be used as there was no need to raise the pressure beyond the factory 43.5psi, and we were not using a 1000HP fuel pump this time around.



Fuel rails shown with PERRIN Pyroshield installed over fuel hose. The OEM rails were used as their ID was plenty large enough.



This was the simplest choice we made, the answer EXEDY Twin plate.  The only item that we didn’t have to worry about working for this build was the clutch. The twin plate can hold 600ft-lbs of torque while feeling nearly as smooth as a stock clutch. Not much more to say about that!


The engine was all assembled and ready to be dropped in. Like dropping in the 4 cylinders, they either slide perfectly onto the tranny, or you fight to get it just right for half an hour.  The engine just flew onto the tranny like it should, and like we hope it all cleared everything. Well kind of.  The super soft OEM engine mounts sag quite a bit more than the stock STI mounts. So much so the uppipe hit the sub frame a little. Out comes the plasma cutter, and we now have clearance.  Next up was the cooling system.


Again keeping its simple, we used an 05 H6 radiator. The H6 engine has coolant inputs on each head, and in turn the radiator needs 2 outputs.  The OEM radiator was the ticket. It’s the same as the STI radiator in thickness so it would at least support 400WHP with the cool weather we have in Oregon.  An interesting find was the stock H6 Thermostat was very hot compared to the STI. We decided to leave it in and see what happens. The amount of coolant the engine takes is basically the same as the STI, so nothing strange there. But there is one fluid that makes it very different than a 4 cylinder.  Luckily I bought a case of oil, because the normal 4 quarts turned in to 7! Yes seven quarts! Now the oil changes are going to $55. Just a small price to pay for big power.


Now that the engine is in, time to connect the turbo to the intercooler, and then to the throttle body. Nothing special about this, just started with an off the shelf WRX FMIC kit and added some bends and couplers, and we are done. The throttle body is much closer to the firewall than the STI is, so some modification to the last boost tube was needed.  BOV was placed between the fender well and the throttle body on the boost tube, and it was now time to fire.


PICTURE OF Engine with 3582R. It looks like it is supposed to be there!



With a base fuel map from my good friend Jason, and quick calculation of fueling needed base on the difference of the H6 and STI, it was ready to fire. First some oil priming to ensure there was at least some oil on all the bearings. First click of the key, and BAM!!!  It fired right up! But there was one thing that made me instantly turn the engine off.  A very scary rattle/no bearings/no oil/something wasn’t installed right sound. Fired it again and this time gave it a few seconds, still the noise was there. What could be wrong?? My stomach sank. One more try, this time I would get out and listen.  Fired right up, and just as I was about to get out, I lifted my foot of the clutch and the noise went away. WOW, that was a good feeling. It was just the twin plate Exedy.  Exedy told us that extra noise is normal with these clutches, but WOW, they are noisy!

Now that the scary sounds are gone, the car was allowed to run for an hour, and go through the heating and cooling process a few times. The first thing everyone noted was sound.  That was such a sweet sound, and I was looking forward to reving this baby up. Time to take her home!  Being the trusting person I am, what could go wrong?   Well nothing did, and we had 2 weeks before we left for SEMA. I was definitely going to take it easy for the next couple of weeks.


As with all my past personal cars, water injection was a must. I started looking at the 2D system for my car, which of course is one of the most versatile systems Aquamist makes.  This system is would do everything I need it to do and more. Since we were working on building our SEMA car, a quick email was sent off to Richard, who is a genius BTW, and in no time, a response.  I told Richard what we were doing for SEMA and he was very excited to be part of our car and offered up something special. But he wouldn’t tell me much about this special system. As time passed I started poking at him about building system that would be special to PERRIN with some features I thought were important. With my constant nagging of a dream WI system, I didn’t want to push to hard for a date when the special SEMA WI system would ship. I was getting a little worried. It was now 1 week before SEMA and a box from a far away land showed up.

Holy SHIT! I think were my exact words. I couldn’t believe what Richard had done. I was expecting a pump some nozzles, injectors, bunch of wires, basically a 2D system with a couple extra things thrown in.  Boy was I wrong. This was the craziest, most thought out WI system I have ever seen. Special Nozzle holders, nozzles, pressure check valves, Twin pumps, mounted to a board with nozzles, relays circuit boards, dash display, and all incase in a plexiglass case!  Richard went above and beyond for us for SEMA.


Aquamist port injection nozzles installed. These are special .3mm nozzles with individual nozzle holders.



Close up shot of nozzles and holders. Love these holders!  Wish they included them with their other systems! Hmmmm……



The FIA2 is the injector amplifier used to drive the signal for the Aquamist injector.  (2) Purple solenoids are used to turn on and off flow to the nozzles. One solenoid controls the port injection nozzles, and the other controls the pre-turbo nozzle.



This is where the magic happens!  Twin pumps means 2 times the flow.  Another FIA2 is used to amplify the signal from teh front to the back. You can see the relays, fuse panel, and the injector all nicely mounted on the board.  What you don’t see is the accumulator located between the pumps.  Richard sure spent alot of time on this!


Again, Richard went nuts creating this system for us!  Switch number one is to arm the system, switch number 2 is for checking the level switch.  Port injection on/off, and pre-turbo injection on/off are the last two switches.  The other things you can’t see is the wire harnesses, that connect this all together.  Hmmm…… Dash display……plug and play harness……..nozzle holders………  pump and electronics all mounted on a board……….progressive injection………i got an idea what to do with this!

This relationship would not only pay off for SEMA, but for something else in the near future.

SEMA 2005

Day one of SEMA 2005, the PERRIN H6 STI debuted.  After months of work, and a 2000 mile drive from Portland to LV and back, the car had made it. The payoff was well worth it. It was our first year attending SEMA as a company, and the car was a hit!


Almost too factory.  Many people just walked by thinking just another STI.  Toward the end of the show, we ended up putting a sign, ‘Turbochaged H6″.  But anyone that new what a Subaru engine looked like, knew that something didn’t look quite right.



Picture of our booth at SEMA.  This was our first year at SEMA, and it turned out great!


All of this wouldn’t of happened if it weren’t for my sponsors, and support from my friends and family (not appearing in any order) Special thanks to Dustin Harris, Jeff Sponaugle, Jarrad Bowen, Adam Taft, John Herring, Ben Collins, Adam Koppel, Jason Bluth, Richard of course from Aquamist, Willy Tagliavani from Supertech, Roland at H&R, Andrew Nam from Hydra EMS, John Lietl from PIAA, Toyo, Autopower, the crew at  PDXTuning, and of course my wife for “allowing me” to work on my car more than be at home……

And that concludes the story.

Oh wait, the story is just getting going…..




After the 2000 miles, and a week of standing on our feet, and not sleeping much, we arrived back home.  We took a step back and looked at what we had done.  It was a crazy time leading up to SEMA, and now it was time to take a breath and relax. Ya, for about 1 minute! The next day, the tuning had begun!


One of the most important parts of the build is the tuning. As with any high performance engine anytime you ask more than 2 times the stock power, tuning becomes very important.  With the 4 cylinders, and the experience we have, things like timing curves, fueling needed, and Air Fuel Ratio the engine likes to see, are almost a no brainer.  Who knows what we would find.

Starting with a low 10psi boost setting, and a safe 10.5-1 AFR, the tuning had begun.  After weeks of road tuning, we started to see what AFR it liked to run, and timing it needed.  Like the STI, 10.5-1AFR was way to rich and it seemed to be happier in the 11.5-1 area.  From there it was time to play with the AVLS system.  When to turn it on was the question.  From Hydra it was set to 5500 RPM. This sounded like a good starting point.

The more miles were put on the car, the higher the “redline” became.  Until this point the tuning was going fine, and the redline had slowly increased to 5500rpm. Then the day came when I decided to bump the redline to 6000.  Up until this point the car was fast, but not 400WHP by any means. The first pull and at 5500 the car came to life! It was a little scary, kind of like a huge turbo with big lag.  What changed at 5500RPM?  Oh ya, that is where the lift turned on.

Because of this huge onset of power, I started turning the lift on sooner to see what happens.  The lift was slowly turned down 500 RPM at a time until it felt like it wasn’t getting any faster.  An interesting thing is turning the lift on lower than 3500RPM would actually make the BOV blow off!  This was happening because of the instant onset of the different cam profile, would cause a huge drop in manifold pressure, in turn the pressure in the boost tube was higher causing the BOV to blow off.  This wasn’t going to work, so some where in the 3700-4500 range is where it felt best.  So how would we determine which is the best and most powerful RPM.

From there we turn back to HYDRA and its auto fuel tune feature. This feature is a great way to get fueling close quick.  First was to set lift on point at 6000. Let the ECU do some tuning and save that map. The set the lift on all the time, and let it work some more magic. When comparing both maps created from the auto tuning, there was a very interest dip. With the lift set at 6000, the fuel map was adding fuel up until about 4000-ish RPM, then took a huge dive until the lift came back one. In similar but opposite fashion, with the lift set on all the time, it would remove fuel up until about 4000-ish RPM, then start adding beyond that point.  From comparing both maps, it became pretty obvious 4000RPM would be the magic lift point. At least for the GT3582R turbo, and header setup.


Just a quick shot of the Hydra interface software. It simple, and very easy to figure out. But MAN they need to get rid of that ORANGE back ground! Love that auto tune feature to get your base map going quick.



Now it was time to start turning up the boost!  Slowly but surely the boost climbed from 8psi to 16psi. Obviously 16psi felt way faster than 8psi.  But the question was to go beyond this point?? Because the engine this go around was all a big test, we didn’t know how much power this thing could take, so 16psi it was!


Finally the day came when it was time to dyno the car.  We heard of this place close by, PDXTuning, thought we might try their dyno out J Yes that was a subtle joke.  First pull on the dyno and 420WHP! Now we are talking! With about 20 pulls at 14psi, and further fuel and timing tuning, we bumped the boost to 16psi. 438WHP and we were good to go. This WHP was a commonly seen WHP amongst many STI owners, so this was nothing too special.  It might have been special when we broke 400WHP on our 04 STI back in 2003, but not now a days.  An interesting thing to think about is the HP per cylinder this engine has compared to the 4 cylinder engines.  The rather normal 400WHP seen by many STI owners is becoming a somewhat safe WHP level for the stock STI engine. With 6 cylinders, and 440 WHP, that is only 73WHP per cylinder. That is almost 300WHP on an STI. Which is very safe, and this is with non forged pistons.  With forged pistons in the H6, we were feeling good about this power, it was time to go beat the car up some more.


Picture of  440WHP run with just the drop in pistons.   The rather normal 400WHP seen by many STI owners is becoming a somewhat safe WHP level for the stock STI engine. With 6 cylinders, and 440 WHP, that is only 73WHP per cylinder. That is almost 300WHP on an STI. Which is very very safe and this is with non forged pistons.  This is just showing that the engine isn’t under much stress to get this power.


The thing I grew to love (besides the sound) was how much low end power the car has. To give you an idea, 16psi would be had by 3100RPM, and this is with a GT3582R. The car is unbelievable to drive.  Stock STI turbo spool with GT3076R power, what more could you ask for.  Again because of the unknowns with this engine, we decided to leave the boost at 15-16psi, and see how it goes. Because I have a small “race track” on the way to work, there were many many 4th and 5th gear pulls done to redline, and I was amazed the car was running perfect!  Day after day, pull after pull and more than 400WHP.

As months passed, an interesting thing started happening, burning oil. This only happened under long decels, the eventually under idle conditions.  First thought was this was a crank case vent issue. The engine only had 2 ports and they were on the driver side. Time to start messing with adding more, and better placed vents.  Starting with adding 2 more vents to the drivers side valve cover.  Eventually a crank case vent/oil fill cap vent would be added.  At this point the engine was freely breathing, but still the oil problem. It was pretty minor, as the consumption was about 1 qt a month.

Before we gave up, maybe the turbo was getting too much oil??  So we installed another restrictor, and nothing different, still oil consumption under no load. Maybe the turbo would get too much oil at low RPM and not enough at high RPM.  So we did a test to see how much oil was coming out with at idle.  Hmmm, no oil???   So I reved it up and right around 4000, out came the oil.  Hmmm, that means the car had almost 3000miles of driving with virtually no oil getting to the turbo!  After finding a new CONSTANT oil supply for the turbo, I was worried about the turbo now being bad.  It was perfectly fine, which goes to show Garrett turbos don’t need much oil to function.

Not enough oil drainage was next. So a better straight shot from the turbo to the valve cover was the ticket.  But same thing still burning oil.  But the car was still amazingly fast, and the compression was perfect. So not too much to worry about, and it was time to take the engine to the next level.

SEMA 2006

With all the talk of Time Attacks, Drag racing, and other plans of racing, we thought lets build this H6!  Lets make 1000HP!  Let’s blow the minds of the SUBY community again. We needed a goal, and a reasonable goal was 1000 engine HP, which would be somewhere around 750-800 wheel HP. And of course do this on pump fuel (ok that might be stretching it).  What would we need to do this?  The list started. GT4294 or GT4088R, Sleeves, rods, valve springs, Ti retainers, head work, new header, and even a larger IC was discussed. A couple of things had to remain; this car still had to be drivable, and had to run on pump fuel.  Also boost response was important, as was low end power, there was no way I was going to sacrifice this.  So we would start with the Gt4088R.  It can flow enough air for 700 engine HP and get us close to where we need to be.  But with this turbo, the only way to break into the 750 area, would be with nitrous.  If this turbo turned out to not flow quite enough, we could always replace it with the bigger GT4294R. But, one step at a time.


So the second time around, we created a list of what needed to be done.  Sleeves, rods, valve springs head studs and retainers were the biggest part of the list.  Using some contacts from PDXTuning, the sleeves were on the way.  A set of rods and OEM dimensions were sent to Pauter to get the rods going. The valve springs were just like everything else, they had to be made.  Off went a head with cams and valves to Supertech. Saying all that in a couple of sentences makes it sound easy, that just wasn’t the case.  As with all special projects, the delivery dates started with one date, then changed, and then changed again, and finally when the parts were about to show up, they got delayed again. After a couple of months, parts started showing up.  Time to pull the H6, and start removing parts.

I was kind of hoping to find out what was causing the burning oil. From constant checking of spark plugs and compression tests, we knew it was something with cylinder #1.  With the heads off, everything seemed to be fine with valve stem seals, but there was some oil in the combustion chamber.  So next was the piston.  As the piston in question slid out, it was kind of like 2001 a space odessy.  In slow motion, the top of the piston is seen…….. then the first compression ring popped out……….then the second popped………now here comes the oil scrapper rings……….top ring….wavy ring, and……….hmmm.  Nothing.  Ah, that would be the problem!  Man that was a relief.  In case you didn’t know, you need ALL the piston rings in order for the engine to function properly. I will have to remember that one J.  Yes, it was an oops, and a big one, but hey, oops happens.


Of all the things done to the H6 block, this was the one item that many of us argued about actually needing.  The funny thing with sleeves is they are not that expensive to buy.  But installation is a different story. The single largest cost involved with building the H6 engine is one of the cheapest parts.  This duty was left up to a local engine builder. As was balancing of the rotating parts and assembly of the bottom end.  For an extra $400 we got a warranty, and a professional engine builder to build the block.  Sounds good to me, so I thought.


This was one of the nicest looking part of the build. Freshly machined iron, and brand new Supertech pistons, are amazing looking.  They won’t look like this ever again!



When the stock rods were pulled out of the block to be sent off to Pauter, something a little scary was discovered.  Putting the STI rod, the WRX rod, and the H6 rod next to one another, made it look like those little chickens that fit in side of one another.  The H6 rod was a joke compared to the other rods. It was thinner in all directions, and it was much lighter. In this case lighter wasn’t better. Like other Pauter products, the custom H6 rods were amazing. The finish was amazing, and they came with ARP bolts, like all good rods. Too bad no one would see them!

Above pics show the difference in the Pauter H6 rod, vs. the OEM STI rod, and the H6 rod.  Its pretty visably different.   Besides the side profile shown here, turn them 90 degrees and you will see another huge difference.  They are much thinner in all directions.



Shows the side profile of the rods installed in the block.  You can see the oil gallery plugs. Behind them are huge ports feeding each of the rods, and main bearings.  Also visable is the lack of the pan. This large surface is where the lower block/pan bolts to.



Supertech was amazingly fast with getting us valve springs and ti retainers. This was a very critical part for the build as the OEM springs were a joke. The rates are so low that the Supertech springs for the exhaust side were almost 3 times higher rate!  Needless to say, after installation of the springs, the heads would be good to rev to 8000 and maybe 8500. But at this point,  who knows if this is even necessary.  We will soon find out.  Now what to hold the heads to the block?  That’s easy, ARP.


Again, more parts we hope to never see again! Installing springs on the heads were very simple on the exhaust side. But the intake side with the variable valve lift, forget it!  the added depth to each buckets bore, made it a 2 man job!



As with any Subaru 4 cylinder build, stock head studs don’t cut it when you are doubling or tripling the power. The stock H6 head bolts are similar to the STI in that they are a bolt.  That is where the similarities stop!  The biggest difference is the bolt is an socket head bolt not a 12point hex bolt. The problem is that the head of the bolt didn’t have much material to support the added torque, and with the stress this engine would see, they were not going to cut it.  Also they were 1mm smaller diameter than an STI head bolt.  So we turned to ARP. The only choice as far as I am concerned.  Custom length and diameter studs from them took way too long, and this engine build was starting to wrap up.  So another solution was needed.  With some quick measuring, we found modifying an STI head stud from ARP would work.  We just needed a spacer between the head and nut for the stud. Some simple 4130 steel spacers, and problem solved.  This time the build went much smoother.  We were still using the manual for torque specs and sequences, but the assembly felt more like the 4 cylinders.


An integral part to the build is is the head studs. There is no way we were going to use the OEM bolts to try to hold 800HP.



This time around it was time for a new paint job.  A couple of stencils for PERRIN, and PDX and it looked great.  Hope this never has to come apart again!



After the engine was all back together, it was time to figure out where the GT4088R would fit. Since this turbo is a twin entry (or Twin Scroll) turbo, it might be a good time to do a complete redesign of the header. In similar design to the first header, the 3 ports would collect about 8″ from the head. From this point is where it changed. Each side of the engine had its own collector and secondary tube. Each secondary tube would power its own scroll of the turbo.  So the header could be called a 6-2-turbo. Because of the firing order of the engine, this setup would provide nice equally spaced pulses for each of the turbo’s scrolls.


It was a long process, but it was really fun building the header.  If you see a production H6 kit, expect the header to look just like this.



Very tight quarters, but packaged like it would from Subaru.  Well kind of.



There is more of those TIAL 44mm Flanges.  The subframe was cut in order for header to clear.  Because there is no real structural member after these points, it was not big deal.


This was a very time consuming project, but in the end it paid off very well.  With the turbo mounted in the magic place, and the twin scroll header set up, we could build the downpipe and be done. The GT4088R uses a 3″ V-band outlet which is such a nice clean setup, until you have to use them and remove them.  As nice as these are, they are a pain in the ass to deal with as you have to get them lined up just right before you tighten the clamp. But who cares, it wasn’t like I was going to pulling the DP off all time, right??

And not to leave out the Wastegate.  Just like our other Rotated Turbo kits, we used a Tial 44mm gate. Since the header was a twin scroll header, we didn’t want to destroy the equal pulses entering the turbo.  Normally people would just stick (2) wastegates on each scroll and call it good. Since nothing else on this engine is normal, we would make a special single wastegate work.  With some carefully welded tubes, and dividers, we created a perfect single wastegate for a twin scroll setup.


One of the things we discovered with the first build is the engine runs pretty hot.  An oil cooler was added this time around to ensure the oil stayed nice and cool, and maybe help keep coolant temps in control.  Of course this adds even more oil to each fill, and makes the oil changes about the same a big diesel truck!  Like we said, the engine runs hot, hotter than the 4 cylinders by about 5-10C.  So next up is a radiator.  A Koyo radiator was purchased, and modified with 2 entry points for the H6 engine.  We also added the STI thermostat, which is 5degrees C cooler. All this should help control temps for any situation.


WRX fog light used for a vent for the oil cooler.



In making room for the header, we had to find a new place for the filter, and OEM oil cooler/warmer.   Why not use a WRX fog light cover and put the heat exchanger behind it.



Another shot of the packaging.  We kept the header as close to the engine as we thought was exceptable. This was important as we didn’t want to be boucing the header off speed bumps, and boulders.



So a little more oil, and a little more coolant than the last build, and she is ready fire!  Just like the time before, it fired right up.  Went through a few heat cycles, and now some quick drives.  Not knowing what kind of oil supply this turbo needed, we discovered an extra restrictor beyond the one was needed. In fact so was a second, so three total.  We definitely weren’t worried about the turbo not getting enough oil J.  So, now it was just a matter of time to break the engine in. No plans for another LV trip so it would be a few weeks before it was ready.

First impressions, was it was laggy.  Before, we would get full boost by 3100 RPM, and now it seemed much worse. But I wouldn’t judge this until the engine was all nice and broken in. So low 8psi of boost was ran, and slowly but surely the RPMS were raised up.


Then the day came that 500 miles were on the odometer. So I decided to do a pull to 7000RPM. First a 6000, then 6500. But I noticed a strange sound. My stomach started hurting, as this sound was rod knock type sound. This was bad!  Babying the car back to work the next day, the sound got worse and valve train noise starting happening.  This is not good.  The engine came out, and was disassembled.  Sure enough, rod bearing #2 has a little more clearance than the rest.  Say about 50 times more clearance!   Thank goodness we paid the engine builder to assemble it, because it would have a warranty, right??  WRONG!!

The builder of course blamed it on oil supply, or improper break-in, not enough oil pressure, too much boost,  or knock, but nothing that they did of course.  Being a reasonable person, I looked into his suggestions.  Boost didn’t cause it, knock didn’t cause it (have logs), so I looked to oil.  Plenty of oil was in the engine and not a bit was ever consumed.  Oil pressure, ya right this thing runs 100+psi, and that wasn’t’ the problem. The argument back was that was way too high, and the added friction from the added pressure could have broken down the oil (due to heat), and caused this.  I don’t buy this at all, as all JDM STI’s have shims to add oil pressure. It basically came down to there were too many things that could have caused it, none of which could be proven it was their fault or mine.


Now that SEMA is approaching quickly, plans started changing.  With the H6 broken, the Legacy Spec B and STI Limited coming out, we thought for SEMA we would show off a different side of PERRIN. Something that better represents what we really do. Plus the H6 was there last year, so its old news!  The H6 is a great show piece, but it’s not like we are building these all day long and selling them. So the focus on the H6 project was turned to a brand new Spec-B Legacy, and Limited STI sitting at the shop.  In great contrast to the H6 build, these would be much simpler and much less stressful builds.  This sounded good with SEMA quickly approaching.  We built the cars to show off what any customer could build using our catalog.  They were great hit at SEMA, and it was nice not having to throw together the H6 at the last minute.


Now that we were back at home, H6 was on my mind, and Subiefest was quickly approaching.  At this point I am not happy with the bearing failure. I thought I did everything by the book.  Starting with the basics of the engine I started checking into things like oil pressure, and oil pump flow.  These were important things to figure out for the third time around as we didn’t want another failure.  I figured I would talk to the builder about the rod bearings and the clearances they had before assembly. Thinking maybe the failed one was tight or loose.  Then I find out that the builder couldn’t tell me any of the clearances of the bearings!  Didn’t write them down!! WHAT!!!

Still not happy, and now doubting the engine builder, the engine, and many other things surrounding how well this will hold up.  Well another $2000 and it runs again. Long story short, everything went back together just fine, but this time we are going to 1000 miles for the break in at low boost and RPM. I would like to pretend this didn’t happen, and it was all a bad dream.


Last time i would be assembling the H6 in 2006.  The paint held up ok the 2nd time around. If there was a 3rd time around, i would be throwing this thing through the window of the machine shop.



I would like to pretend this didn’t happen, and it was all a bad dream. Subiefest 2006 was the maiden voyage of the freshly re-built, re-honed, re-balance, re-ringed, re-bearinged engine, and it went perfect!  It was also the first time the public had seen the new engine, and turbo combo. Besides the few people that walked by casually thinking it was just another STI engine, the car/new engine was a hit! Plus we got to put tons of miles on the engine and lots of great road tuning.

1500 miles and time to put in synthetic oil and take this baby to the dyno!


First pull on the dyno wasn’t as good as the first pull done months prior, but we were running less boost. None the less, it made decent power, and at the starting point of 14psi there was tons more on tap!  With further tuning at 16psi we realized there was major gains to be had. At this point in the tuning, most of the time was spent getting the fueling close. The timing curves we had from the previous tune was pretty good, and we didn’t want to push the limits too far.  As we found, this engine would make more power with boost, not timing.  The goal with this tuning session is see what kind of “easy” power we have on tap.  We were not going to be pushing this engine this time around.  Also this is on pump fuel, with water injection using a 50/50 mixture.  All runs below are named by the boost seen at peak power. Example: The 16psi run is running 16psi at 6500, and a little more at 4000.



Above graph is 16psi with some fuel and timing tuning. By the change in this graph you would think the engine was running near misfire, but this was running 10.5-1 vs 11.5-1, with a couple degrees in timing change. We were trying to hit 500, but it just wasn’t going happen.  Time to turn the boost up some more!



Above graph is 18psi.  Again that is 18psi at 6500RPM. The large dip in the graph was from the engine running a bit rich on initial spool.  Like seen at 14psi, fueling makes a big difference, this dip was .7AFR change.  4psi and we gain 80WHP and 80ft-lbs of torque, this is starting to look good!



Here is the boost curve of theGT4088R on the H6. The only change in the hydra between runs was a simple change in the boost target map. As far as changing boost, the HYDRA is very simple to do. The only thing we battled with is a falling boost curve. The spike at lower RPMs really helps with torque, but if we could only hold it!!



Yes it was called 22psi, but at peak power, it was 21psi.  Again 4psi and some great gains!  But we are starting to see the gains not so exponential, compared to lower boost levels. This is a sure sign of turbo starting to run out of air flow.  More on this later.  During the last few runs we started to see the boost curve spiking a little more, but it would still hit the target, 22psi.



Now the 2psi of boost change only netted about 20HP.  During the last few runs we started to see running a little lean close to redline.  First small amounts of fuel were added, then larger and larger with no changes to AFR.  We were SO close!  Well that Walbro was good while it lasted!  As we once thought before, the fuel pump wouldn’t be enough for to much more than the 500WHP, but it at least allowed us to hit 600!



Well there you go 600WHP!  It was limited by fueling, but even if we had fueling dialed, I don’t think there was too much more power to be had. Running more boost means more air flow, more air flow means we are going to be way off the compressor map.  Going off the compressor maps means turbo efficiency goes down the crapper, and in turn less potential power.



Here is the boost curve of the 600WHP run and the 22psi run.  Couple things here to take note of:  The actual boost needed at peak power to hit 600 WHP was just over 23psi! In contrast a 30R on an STI barely breaks 400WHP at that boost.



Air flow = HP and boost pressure = more air flow.  How ever you want to look at it, this turbo isn’t big enough to flow too much more air or make too much more HP.  Below are some lbs/min ratings of the 3.0L at difference boosts and RPMs.

So at 7000RPM and 16psi of boost flows 58lbs/min of air.  According to how Garrett rates their turbos HP, that is about 580 engine HP. Since we made 470Wheel HP, and if we use a 25% drive train loss, we get 580HP.  Sounds about right.  At 23psi and 7000RPM, the engine is flowing 73lbs/min, which is about 730 engine HP.  With drive train loss, that puts our 600 Wheel HP at about 750.  Again pretty close.


COMPRESSOR MAP OF GT4088R.  You can see using a basic air flow calculator that not too much more power would be had.  Esspecially on pump fuel.  But 600WHP on pump fuel, what more could you ask for.  Thought this wouldn’t be possible without water injection.


Since the turbo is only rated for 700 engine HP, according to Garrett, it is no surprise that we started to see diminishing returns as we got closer to 23psi. The word diminishing is not the best word to use as we were still making huge power. You can see by the compressor map that we were getting into the areas where the turbo was less and less efficient. Again showing why at high boost levels the gains were not as big as the boost went up.

So was there tons more on tap?  Nope!  Can the H6 hold more power if there was??  I think so.   With the progression of power, and how easy it was to get there, and with power coming so easy with ZERO knock, there is sure good signs that it can.  Think of this build as WHP per cylinders.  600WHP on the H6 is 100WHP per cylinder.  100WHP per cylinder on a 4 cylinder is 400WHP, which many consider and have proven to be safe (with non-forged piston engine). To get 600WHP on a 4 Cylinder you will be at 150WHP per cylinder. That is 50% more stress, and pressure.  If we use the example of a forged piston, stock sleeved STI motor, holding almost 600WHP (150WHP per cylinder), the H6 would be good for at least 900WHP. That is pretty scary!  Add sleeves into this, and say 1200?? Thats only 50% more power per cylinder.  But that is all speculation, and stepping into dream land.

So why didn’t we go too much further? Fuel. As we got closer to 600WHP, we noticed that we were adding more fuel and nothing was happening.  A PERRIN chassis fuel system is the easy answer to fueling and making it 100% safe to run at 600WHP. As many have found, 550WHP is kind of the limit of the Walbro, and we just proved that stat isn’t too far off.  As important as fuel is to this build, it is one of the simplest things to fix. This will allow, I believe, a safe 620-640WHP. But to go beyond that, it would be time for a bigger turbo.


Most likely nothing. At this point we have awesome power with 4000RPM of spool. Any bigger turbo and we will sacrifice spool and all the low end power we just gained with the bigger engine.  If we did go bigger, the next best choice is the GT4094R, but the extra 100 possible HP would only be for showing off.  At 500WHP, this car was pretty scary, add 100WP to that and it just became a dry weather only car!  In the state of tune it is in, it is far faster than most all other supercars at 1/2  to 1/8 the cost depending on if you compare it to a Z06, or a Ferrari.  This car isn’t a trailer queen, or a dedicated drag car, or dedicated track car, or street car.  It may not be the best at those things, but it sure will do well at all of them.


The one thing that will happen next is fuel.  We need more fuel to get more power.  The PERRIN fuel system and pump are installed and ready to do a retune at 600WHP!  Above is just one part of the system.  A fuel pressure regualtor.



Alright, now the fun stuff.  So how does this compare to your normal everyday STI’s driving around out there?  From all the info above, you can probably conclude it has more power. This is true, but it is kind of fun to see exactly how much and where it dominates the 4 cylinder.


The first comparo is our 07 STI limited. I think this is the best comparo as this is a very common setup. The 07 STI Limited uses a Full PERRIN package. Every single bolt on part we do is on this car. The rotated turbo we used is a GT3076R with a .82AR exhaust housing.  Running a modest 21psi boost level this setup can hit 400WHP pretty easy. And this graph shows it.  With similar spool to the Gt4088R on the H6, it does nothing but STOMP it everywhere!


The second comparo is highly tuned stage 2 STI. Again this is a good comparison as this is another common setup.  This car only has a slight edge below 4000RPM. But when you are racing, auto crossing, dragging, you will not be in this range very long, so again the H6 wins!  But on the road, below 4000, the Stage 2 STI will be much faster.



This comparo is a highly tuned GT3076R STI.  Again this is a good comparison as this shows a similar spooling and similar low end power car with the H6.  This GT3076R is really maxed out and on the 4 cylinder, a GT3582R will get close, but at the sacrifice of low end power.



The last comparo is a highly tuned GT3782 on an STI.  This turbo flows about the same amount of air as a GT3582R, but with a freer flowing turbine wheel.   Again this is a good comparison as this shows a 4 cylinder making about the same amount of power as the H6. But you can see what kind of sacrifices you make to get there.  On the road, there is about 1000RPM different spool, and about 13psi more boost on the 4 cylinder.  With the H6 running about 23psi to get this power, adding 13psi to the 4 cylinder to get close to this power, you are going to start having issues with head gaskets sealing, bearing taking a beating and quite a bit more stress.


The question is would I do this again?  One could argue that the power levels we reached could be done with a 4 cylinder.  One could argue that you would also save a ton of money doing the 4 cylinder. One could argue that the added weight will hurt handling. One could argue that it gets worse gas mileage.  One could argue that it is untested waters.  One could argue that 600 is way too much power for a street car.

I say so What!   I think it is time to start a trend for a new Subaru Exhaust Note!   Bye bye Boxer-rumble, here comes the boxer-smoothie…………or boxer-Porsche-aru, or boxer-Sub-orsche, or something that represents that it sounds like a Porsche.




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