This Perrin Catted Downpipe is perfect for those looking for performance gains similar to a catless downpipe, but still would like to retain some of the stock characteristics.
Their new modular design allows you to replace the section with a fried catalyst and/or build the system as you can afford to. Performance gains will be comparable to a catless downpipe as the high-flow catalysts in the Perrin WRX/STi two-piece downpipe are extremely non-restrictive. The Perrin two-piece downpipe for the WRX, STi and Forester XT is perfect for those looking for performance gains similar to a catless downpipe, but need to keep catalysts in the system due to emission, tuning and racing specifications.
Some of the main features include 3" polished 304 stainless steel piping with a wastegate diverter. The wastegate diverter separates unused exhaust gases from the exhaust stream and then channels them back into the system further down the line to reduce turbulence. The result is smooth, maximized exhaust flow -- which is a necessity for turbocharged performance. The stock downpipe and some less expensive aftermarket units have a flat flange that makes no provisions for the wastegate,resulting in escaping exhaust getting backed up after the turbo and slowing spool up. Another feature of Perrin's downpipe is 1/2" flanges which eliminate warping and leaking under high temperatures. Perrin backs their downpipes with a one year warranty. This downpipe will attach to any cat-back exhaust system, including stock (except for 2006 WRX's, which will require the purchase of an aftermarket catback exhaust for fitment due to the revised exhaust. 2006 STi's can use this downpipe with stock or aftermarket catback).
02-05 WRX OWNERS READ: On the 02-05 WRX there are no boost spike or creep issues in most cases with the use of an aftermarket downpipe or turboback.
06+ WRX OWNERS READ: On the 06+ WRX there are boost spike or creep issues in all cases with the use of an aftermarket downpipe or turboback. This is because the 2.5L engine pushes so much air. Even with the internal wastegate fully open not enough air can exit to stop spinning the turbo, the result is boost creep or boost spike. With the 06+ WRX, unlike the STi, you cannot fix the problem by just porting the stock turbo wastegate. We suggest porting the stock turbo wastegate AND getting an engine management system to help fix the issue like a UTEC or AccessPORT. With the added costs this will entail 06+ WRX owners may want to consider waiting to get an aftermarket downpipe or turboback after they have upgraded there turbochargers or they may want to consider getting a cat-back exhaust only.
04-06 STi OWNERS READ: On the 04-06 STi there are boost spike or creep issues in all cases with the use of an aftermarket downpipe or turboback that uses a bellmouth or external dump tube design. This is because the 2.5L engine pushes so much air. Even with the internal wastegate fully open not enough air can exit to stop spinning the turbo, the result is boost creep or boost spike. You can fix the problem by porting the stock turbo's wastegate passage (any exhaust shop should be able to do this or it can be done at home) or you can get an engine management system to fix the issue, like a UTEC or AccessPORT.
Usually ships 1-3 days.