Perrin Equal Length Headers for the 2002-2014 WRX & 2004+ STi
The newly revised Perrin E4-Series Equal Length Header the EJ25 come with collectors specifically designed for better exhaust flow for an increase in torque and HP throughout the RPM range. The improved exhaust flow and more precise construction not only increases power it also makes the Perrin headers some of the most reliable long life headers on the market for the EJ25 engine. The new E4-Series offers a low-profile design, allowing for plenty of ground clearance.
The equal length design of the PERRIN E4-Series Header produces smooth, balanced exhaust flow from the heads to the turbocharger giving you the best of two worlds: quicker turbo response as well as more horsepower and torque throughout the entire RPM band. While designed to fit to the factory up-pipe, our header will also mate with an aftermarket up-pipe that fits factory header and turbo, as well as any rotated turbo kits compatible with the factory header.
You won’t see grossly over-sized tubing to make our header “look” impressive, this just slows exhaust gas flow and reduces response. These headers uses 1.5″ primary tubing that is expanded at the flange to fit the Subaru exhaust port size. This size tubing is perfectly designed for cars making 400-600WHP. You can see from our dyno graphs that there is a significant gain in horsepower and torque across the entire RPM band compared to an OEM Subaru header. For those looking to make more than 600WHP Perrin also offers a “big runner” header that use a huge 1.65″ primary perfect for any EJ25 build looking to make 600-1500WHP.
PERRIN Flanges are CNC machined from 304 stainless steel and counterbored on the back side to make smoother transitions. Flange ports are sized properly to ensure exhaust coming out of the head has a smooth, unobstructed path to the tubes. The ports are not over-ported which would cause gaskets to burn out quickly. The tubes are expanded inside the flanges for a perfect fit and smooth flow of exhaust gases to the tubes.
Due to its equal length design, the PERRIN header will alter the tone of your exhaust. The exhaust pulses from the engine are equalized and spread out producing a smoother, more refined sound. Don’t miss understand, your Subaru will still sound like a Subaru it will just have a much cleaner smoother Boxer rumble. A byproduct of the equalization is a significant reduction in the volume of your exhaust sound at low loads/cruising.
Most headers collect on the passenger side of the engine, and due to space constraints, are not equal length and compromise exhaust flow. Because we use the added room provided by the oil pan (only on 2.5L turbo pans), we can create a smooth transition of the header primaries to the collectors, and collectors to up-pipe, providing more power and torque then the competition. 2.0L WRX engines will need the 2.5L STI oil pan install kit.
2002-2005 WRX – Yes, requires oil pan with header cutout and oil pickup tube
2002-2005 WRX Automatic Transmission – Yes, requires modifications to radiator and radiator line to the transmission
2006-2007 WRX – Yes, requires 2002-04 WRX oil cooler assembly and oil feed pipe
2004-2008 Forester XT – Yes, requires oil pan with header cutout, oil pickup tube, 2002-04 WRX oil cooler assembly, and 2002-04 WRX oil feed pipe
CSF Radiator with Built-in Oil Cooler – No
KILLERB Cast Oil Pan – No