Modification of Exhaust for Subaru Cars
The primary purpose of an aftermarket exhaust is to remove or replace the stock catalytic converter(s) with a better flowing unit. It also increases the exhaust diameter for better flow. The term "aftermarket exhaust" can be broken down into the three main types: 1. Turbo back exhaust (TBE) covers items 1-4 as described below. 2. Cat back exhaust (CBE) covers items 3&4 as described below. 3. Axle back exhaust (ABE) covers item 4 as described below. The stock Subaru exhaust consists of: 1. Downpipe (with cat) 2. Midpipe (with cat) 3. Rear Exhaust Pipe 4. Axle Back Muffler HP gain is dependent on the type of exhaust chosen. TBE gains are 20-30HP . CBE gains are 5- 15HP . ABE gains are 5-10HP . These figures are highly debated as different manufacturers use different dynos with different cars with different levels of mods. It also varies because exhausts use different amounts of catalytic converters or are catless.