Muffler and Exhaust testing

[JBrady]

Here is an article that may be helpful to understanding what gains and losses are found in an exhaust.

Test engine is a large 455cid/7.5 liter OHV Pontiac V8.

Mufflers were tested as a SINGLE to magnify the differences.

Between open headers and a single muffler the maximum difference in 1/4 mile testing was only 2.4 tenths from a 12.97 to a 13.22 and 2.6 mph from 102.6 mph to 105.1 mph.

Remember, this is with a SINGLE 2.5" muffler on a 7.5 liter engine.

Interesting nearly the best muffler tested was a turbo style which has 3 internal tubes.

This muffler as a SINGLE 2.5" I/O muffler lost only 6 mph and 0.8 tenths in the 1/4 mile (about 6-8hp lost over open headers).

http://www.pontiacstreetperformance.com/psp/exhaust.html

 

[jibbby]

Mufflers, one would think straight thru mufflers would work the best for performance applications... I've yet to seen any oval muffler outperform a high performace straight thru muffler on any street driven cars... Other such mufflers as stated above is more designed for noise control and some performance..... This is why I think you may see straight thru performance mufflers on most motorcycles..

Right or wrong?

The trick with straight thru's is controlling the loud exhaust sounds... High flowing resonators help but then again if you start restricting sound you usually start restricting performance......

 

[EyesofThunder]

I commonly post Jim Hand's story on exhaust. People argue that you can't have flow without loud noise. Yes, the dyno and the quarter mile and sound meter prove it.

Old thread, but very worthy good read on this story.

Also gives idea, Jim ran low 12's on 2.5" duals with a 7.5L 455 Pontiac (shifts around 5700, 455's are heavy and make a ton of power and don't need to spin crazy high to make power)