Nov 062013
 
Updated from July 2010 post with new pics and new data!
When Subaru released the Version 8 STI in Japan we noticed how they moved to a twin scroll turbo and equal length exhaust manifold. This is what inspired us to make our first header for the WRX/STI! Would taking the equal length design of this JDM header and adapting it to fit our US cars actually make a difference in power? Would it spool worse?  How would the sound change?

DESIGN

The design of the PERRIN equal length is very different from the rest of our competition.  You will not find huge oversized tubing here just to make it look cool.  You will find proper sized tubing designed for the perfect balance of response and HP for applications beyond 400WHP.   Since all of the 2.5L turbo engines come with an oil pan with a large cutout in the side this allows us to build it similar to the JDM header that inspired us. Many other headers collect on the passenger side of the engine, and due to space constraints can”t be truly equal length without compromising flow, and clearances.  Because we use the added room around the oil pan, we can create a smooth transition of the header primaries to the collectors, and from collectors to the uppipe connection. This is why our header makes power across the entire RPM band.

A small but important feature to our header is that it is designed to fit to the factory uppipe. This allows for simple installation to either an OEM uppipe, aftermarket uppipe, and our rotated turbo kits.This is important you can upgrade any part of the system when you choose to.

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POWER

The biggest question is, does it add HP and do it without losing any response? We tested this on many applications, but below you will see HP results that cover most every customer we deal with. In the past headers were a trade-off.  Some top end power was gained where some low end power, and boost response was lost. Also the minimal gains made the Cost vs. HP scenario not look so hot.  As we (and customers) have proven, the equal length design of the PERRIN header, gives you the best of both worlds.  Tons of low end power gained and still the top end power.  We find a minimum of 30Ft-lbs of torque gained at lower RPM, and around 15ft-lbs everywhere else. Same goes for Wheel HP, roughly 30WHP at lower RPM,and about 15wHP every where else.  Talk about the Cost vs. HP scenario looking good!

Results: Stage 3 Legacy GT

This graph illustrates the significant torque gains throughout the power band.  This car was a 2005 Legacy GT with a Stage 3 setup.  This includes a PERRIN TMIC, ECU retune, Turboback exhaust and uppipe installed. The only change between runs was the OEM header for the PERRIN Header.  More than 20WHP and 30ft-lbs of torque was gained!  This Graph also represents what you would see on a 2008+ WRX.

dyno_header_lgthdrcomparison

Results: Stage 2 STI

Below is a test a Nasioc Member did on a stage 2 STI. This car had just an ECU flash and turbo back which represents the most common setup we see on an STI. The only change between runs was the OEM header for the PERRIN Header, no ECU tuning!  More than 15WHP and 20ft-lbs of torque was gained!

dyno_header_stockvperrin

 

Results: STI with a GT3582R Rotated Turbo Kit

This graph illustrates how the header works on a car with a huge GT3582R Turbo.  This has has many modifications to support the huge power from this turbo.  The only change between runs was the OEM header for the PERRIN Header, no ECU tuning!  With the boost at a reasonable 22psi and again no other changes between runs, 10WHP was gained up top.  But where this header really shines, is at lower RPMS where it spools the turbo quicker making 30WHP and 50ft-lbs fo TQ. Graph provided by NASIOC member Tim Gentil.

gt35rheadertest

This below graph illustrates the boost response of the car above. You can see how changing the header makes the turbo spool quicker.  At 22psi the turbo spools quicker by almost 500 RPM!  Graph provided by NASIOC member Tim Gentil.

dyno_header_hdrboostresponse

 

NASIOC Test of 5 Headers

The below test is another one done on a public forum using and independent tester and dyno. Of the 5 headers, there was a clear winner and a clear loser. The stock header was the lowest HP and the PERRIN was the highest. The other headers are some of the other popular headers as well as a ported stock header.

NASIOCheadercomparo

 

 

SOUND

The only downfall with the header is the loss of the Subaru sound.  The lumpy, thumpy boxer sound everyone has come to love becomes a nice smooth buttery sound, for everyone to fall in love with all over again.  Because of the unequal nature of the OEM header, the exhaust pulses are paired together causing that lumpy sound.  The PERRIN header changes the note of the exhaust because the sound pulses from the exhaust are equalized and spread out, causing the smoother, more refined sound coming from the exhaust. This is a love/hate kind of a thing. You either are a die hard “boxer rumble” guy and don’t care about the added power, or someone who is looking for a nicer more refined sound that wants the most from their Subaru.

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CONSTRUCTION

The headers are made from mandrel bent 304 stainless steel tubing that is TIG welded throughout and use CNC machined 304 SS flanges. This high end type of manufacturing is how all our exhaust parts are made, but the flanges are what really make our parts stand out.

As you see, our flanges are counterbored for smoother transitions from tubing to the inside of the flange. The other important thing to take note of is the center bores of each flange (smallest hole). These are also matched to their mating parts to ensure a smoother exhaust flow and ensure the gaskets will seal properly. Look at our competition and you will see how they make the flange holes as big as possible to give the appearance they flow more and make more power. You will also see the customers using these other headers constantly fight gaskets blowing out because the larger holes leave the gaskets exposed to the extremely high exhaust temps. We make the flanges the correct size to ensure the fire ring on OEM gaskets are kept away form the high exhaust gases to ensure your gasket will last a very long time.

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Oil Pan and Installation of Header on 2.0L Engines

Since the 04 STI was released with the oil pan with the large cut-out on the right side, this allowed us added room to create a smooth transition of the header primaries to the collectors, and collectors to uppipe. The problem is not all cars have this oil pan, and some cars do not have the same oil cooler to allow the PERRIN Header to fit. This affects the 2002-07 WRX and there are a few things that need to be modified in order to allow it to fit. Below is the info and part numbers needed to help guide you through the necessary steps to get the PERRIN Equal Length Header installed on your 02-07 WRX.

For the 02-05 WRX (2.0L engine) the modification is simple. You need to replace your oil pan and oil pick up with the parts from a 2004-2014 STI. Besides the installation being a bit messy, this is not a very hard job to do. A DIY’er might take 4 hours total with cleaning and reinstallation.

For the 06-07 WRX (2.5L engine) the car has the correct oil pan, but Subaru installed a weird oil cooler. These cars come with an oil cooler that is angled back toward the rear of the car, which causes interference with our header. These cars you need to purchase the oil cooler, and oil feed pipe from an 02-04 WRX or 04-14 STI. These cars require quite a few things to be removed, see the below diagram.

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COMPATIBILITY

2002-2005 WRX *Requires STI type oil pan and oil pickup.
2006-2007 WRX *Requires modification to the oil cooler (Please call for details.)
2004-2005 Forester XT *Requires STI type oil pan, oil pickup, and 02-04 WRX oil cooler.
2006+ Forester XT *Requires the 02-04 WRX oil cooler.
2004-2007 STI Yes, No modification
2005-2009 Legacy GT Yes, No modification
2008+ WRX Yes, No modification
2008+- STI Yes, No modification

*OEM PARTS

Oil Pan with Header Cutout Subaru Part #11109aa151 - Est. Price $108.28
Oil Pick Up Tube Subaru Part #15049aa110 - Est. Price $26.98
Oil Cooler Assembly Subaru Part #21311aa051 - Est. Price $219.95
Oil Feed Pipe Subaru Part #21317aa02 - Est. Price $43.38
O-ring (not needed unless damaged) Subaru Part #21370ka00 - Est. Price $5.82

 

 

Counter Bullet Points

  • Ours- Proven 15-20WHP gain on all cars. Done publically and on our own dyno.
  • Theirs- Claimed HP never matches what people see on the dyno.
  • Ours- CNC machined 304SS flanges with counterbores for smoother transitions.
  • Theirs- Mild Steel then Chrome plated to keep flange from rusting.
  • Ours- Tig welded on the outside of each flange connection
  • Theirs- Welded on outside and inside, which causes lots of stress on the inner tubing and will crack.
  • Ours- Perfect sized tubing to make power 15-20WHP on any size turbo
  • Theirs- Oversized to look cooler! 
  • Ours- No flex joints!
  • Theirs-Flex joints installed that blow out over time due to extreme pressure and temperature.
  • Ours- Made 100% in the USA!
  • Theirs- Made overseas somewhere….
  • Ours- Fits with factory uppipe and the PERRIN  uppipe.
  • Theirs- Sometimes requires their uppipe which cost more and adds more time to the install.

 

Check out the BIG Tube Header Blog Post!