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.

 

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.

 

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

 

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

 

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