Matt's 95 Stang

Has anyone seen, or know of any dyno feedback for our 3.7s based on exhaust size? More specifically if they benefit more from 2.25'' exhaust cat back pipe size vs 2.5''? I ask as I am getting Magnaflow Competition axle backs which are 2.5'' inlet where the rest of our piping is 2.25. I would like to replace the factory piping as I have seen how bent and restrictive the OEM pipe is.

Thanks!
Matthew

13V6coupe

so did you have this done and have some results to share. Seems no one else had an experience with this.

Matt's 95 Stang

No not yet. I am going to wait a few weeks and see if anyone has anything to say. If not I will just take the plunge and do a custom 2.5 hybrid H/X pipe.

Matthew

289hipo

My MBRP axle back is 2.5 which fitted over my 2.25 factory pipes without a problem.

Derf00

You can go with a larger diameter pipe if you want but there will be zero performace gains from it. If anything you may lose a little on the low end. This is not due to backpressure (internet folklore) but to a reduction in scavenging affect.

The scavenging effect is created by the velocity of the exhaust in the exhaust pipes that creates a weak vacuum at the head. This weak vacuum helps to pull out the exhaust from the combustion chamber during the exhaust phase. When you increase the exhaust tubing diameter you reduce the velocity of the exhaust gases and therefore lower the amount of vacuum. This lower vacuum will reduce the scavenging effect and thus lower the power a smidge. In most cases you won't notice it by butt dyno. Only on a real dyno...unless you go like 3" exhaust...

There are more technical articles than this but it's the general principle in a nut shell.

http://en.wikipedia.org/wiki/Scavenging_(automotive)

cruisin5268d

Stick with the stock size.