Exhaust size vs hp

[Car #4]

How does going to a smaller exhaust produce more hp? To my thinking larger exhaust would allow more airflow through the engine and therefore you could supply more fuel.

 

[Black_Sheep]

I think you’re misunderstanding the text. It’s saying that there was a 7 horsepower gain by switching from 2.25” to 2.5” headpipes…

 

[Thunderdan]

Additionally, the further downstream in the exhaust system you neck the pipes down in diameter, the less impact it will have on performance due to exhaust gases cooling and pressure correspondingly dropping.

 

[Car #4]

I think you’re misunderstanding the text. It’s saying that there was a 7 horsepower gain by switching from 2.25” to 2.5” headpipes…

I had to read it a couple more times but ya, your right. My oops.

 

[R413]

My friend had 3" exhaust with stock GTX tips welded to the ends. He thought that was slowing his car down, he swapped to wide open large tips. Made zero difference.

He raced the car and had plenty of time slips, so it was a real test, not a seat of the pants jundgement call.

 

[33 IMP]

Theoretically, a too-big exhaust system can sacrifice torque .
I have two cars with too-big exhaust, headers and muffler system. I can't say I've noticed a problem... and I'm not gonna downsize the system hoping to pick up power.

 

[68Moparmaniac]

Talking with the engineers @ TTI they said unless your pushing over 600 HP 3" pipe is a waste of space and money, 2 1/2 is fine for most street applications....

 

[GTX JOHN]

I have a 69 valiant with a 500HP 440 that runs 10's thru
the exhaust. I have run both 2 1/2 and 3 both with no
tailpipes and there was Zero difference in the ET.

 

[33 IMP]

There was an engine masters test, of several exhaust configurations, but the final one came down to a good expensive 2 1/2 muffler and system, verses a cheap 3" muffler and system.... and the 2 1/2 system won. More hp, 2 1/2 pipe cheaper and lighter than the three inch.
Bottom line was, however, that the mufflers were the difference, and an expensive name brand 3" made the most power of all the tests.

 

[AR67GTX]

The C2 Corvettes with 427s ran 2-1/2” pipes undercar all the way to the mufflers just before the rear bumpers, and the muffler outlets/tips were 2”. They still say that is about as good a flowing system as you can put on them and flows better than even up-sized, chambered sidepipes.