would cutting off my stock muffler and welding back on a after market one would that have a horse power increase or would it do anything or would it just make the the car loud and do nothing

 

Is that a serious Question?

You might gain 0.5hp maybe! a Full exhuast system with intake you might get 10hp if your lucky. Real power is made in internal engine parts and Tuning. NOT loud *** cheap mufflers.

 

http://www.nsxprime.com/FAQ/Miscella...austtheory.htm

^^

There lies all the answers to your questions about exhausts

 

Yes it will make power

 

With intakes and header, b-pipe or mufflers you'll either make minimal gains on a stock engine or potentially hurt performance.

Intakes and mufflers often do little more than make more noise in comparison with stock ones.

Also, unless you're getting a universal muffler you shouldn't need to cut and weld anything. The aftermarket mufflers (Spoon, Mugen, Greddy, Apexi, etc.) you will often see mentioned on sites like these bolt right on. No cutting or welding needed.

 

Plain and simple no.

 

You might decrease some back pressure but you will gain minimal if not lose power. honestly its just gonna sound like crap on the stock piping. you can’t go from stock piping to a high flow muffler and get race car sound.

 

Depending on the capability of the motor, it could help. Such as if you have a GSR motor, H22, etc, it may benefit from being able to flow more. I can't recall the numbers, but I know different size exhausts will support certain power ranges. Too small, you choke the motor. Too big, you lose exhaust velocity and hurt performance.

From your user name, I'm assuming you have a '00 Si. Keep the stock exhaust or at most, get an axle back. Let's face it, stock exhausts sound weak, and this is one of the first thing most people like to change. Get something quiet but a little better flowing. An Apexi WS2 or a twin loop muffler could give you a better sound. I don't use my tachometer, so hearing the motor a little is nice for me.

 

A muffler, no. A cat-back could free up some horsepower depending on supporting mods.