ke0ki2k

iTrader: (2)

after readin about several guys who just replaced the cats & y-pipe. if i were to get 2.5 inch test pipes and a 2.5 inch to 3 inch collector Y-pipe, would i need a new Y-back exhaust? ive read that exhausts have proven to give little to nothing in power or torque but several guys ive talked to said that replacing the cats and Y-pipe showed significant gains on dynos. True? not true? discuss.

Ziggyrama

iTrader: (15)

Generally, removing cats from the exhaust will improve gas flow. Keeping exhaust gas velocity up is key to making power so I imagine going catless will make additional power. How much? That I am not sure about but I imagine it will be around 10whp +- a few horses depending how restrictive the factory cats were in the first place.

Is 2.5" y-pipe a good size? Seems big for an NA car. Going too big will hurt the flow. I would think 2.25" catless would be more optimal but it's just my gut feeling. If you're FI, no such thing as too big of an exhaust.

blasian

iTrader: (29)

My friend gained 12whp with his 06. Done on the same day.

Jim@Showstoppers

iTrader: (157)

You'll see around a 10whp gain. Although when coupled with an exhaust you will see a bigger gain.

ke0ki2k

iTrader: (2)

2.5 inch Y's into a 3 inch collector. how wide is the factory mid pipe?