Exhaust, help performance?

[woody89 10+ year member]

I have heard they help a car's performance some, varrying what type you get and many other factors. But people on this "bmx" forum were saying they help in no way at all. That seems false to me. I just read these in some random thread. Are they right?

Some statements like....

If I can stick my fist in your exhaust tip, you're gay. Large daimeter pipe actually hurt more car then they help.

Right. Since a 2.0L motor needs a 5" exhaust tip.

Now when they hear the sound and want to race, you cannot back up the sound. Making you look even more like a fool. Nice.

Wonder whos bright idea that one was. Probably that moron who invented whistle tips or fart cannons

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[Beat_Dominator 5,000+ posts]

I have heard they help a car's performance some, varrying what type you get and many other factors. But people on this "bmx" forum were saying they help in no way at all. That seems false to me. I just read these in some random thread. Are they right?
Some statements like....

If I can stick my fist in your exhaust tip, you're gay. Large daimeter pipe actually hurt more car then they help.

Right. Since a 2.0L motor needs a 5" exhaust tip.

Now when they hear the sound and want to race, you cannot back up the sound. Making you look even more like a fool. Nice.

Wonder whos bright idea that one was. Probably that moron who invented whistle tips or fart cannons

Depends on the circumstances but there are correlations between HP #'s and the diameter of the pipe needed.....anything bigger CAN reduce back-pressure too much and hurt the performance, particular torque numbers.

For instance on my mustang, I'd need to get close to 600hp to require anything bigger than the 2.5" tubing I have now. I did a cat-back and it gained me a whopping 2hp (It's been dynoed). I knew that I'd gain nothing, I did it to get the sound I wanted. So it was purely cosmetic.

 

[IrTehL33T@DBeez 10+ year member]

peak horsepower output has a direct relation to exhaust pipe diameter based on proper exiting velocity from the exhaust ports in the cylinder head, the requirements of diameter to be properly in tune with the engine depends on displacement and compression. high compression and high displacement requires the most free flowing exhaust possible, to maximize the performance by matching the camshaft profiles used with such motors, the which have very high duration, with minimal lift and extreme lobe separation angles.

if you have a lower compression engine, what you will be looking for is an exhaust that provides exacting diameters of the primary exhaust tubes (the ones immediately after the cylinder head) and then a varying diameter thereafter to create an increased exhaust velocity while reducing backpressure before the gases exit the tailpipe. one of the biggest things to avoid is the catalytic convertor, all they do is rob performance because the gases that it effects are actually heat extractors which help create a more stabilized exhaust pressure thru the more controlled temperature. this helps provide the lower performance engines to breathe in more of an open, racing exhaust style without being quite as extreme as the full racing exhausts you'll find on high performance engines.

 

[Airman21 10+ year member]

headers and mid pipe is where the hp's at.. cat-back like said about is mostly for sound