[Pastor Spomer]

I’m coming close to buying a cat back. Most are 3 inches but they taper down to 2.5 inches. What good is having a 3 inch exhaust if it has a 2.5 inch bottle neck? And yet, manufacturers, like Cobb, have the dyno charts to back up their claims of improved performance. I’ve read that to big of a pipe will rob you of low-end power. Is that true?

 

[DOHCammin]

I'm sure cobb/stromung know what they're doing with the 3" and the 2.5" taper, I doubt that the taper would restrict the flow enough to show up as any kind of power loss on a 4wd dyno.

 

[DanzBorin]

actually, when you get into the higher HP game, a true 3" axleback can make a huge difference, but for stage 2/3, it really won't matter...

 

[keyser soze]

When I was inquiring into Catbacks, I was told the tapers were at the standard juctions and were kept so someone could add the aftermarket Axelback, or catback, or full turbo back depending on the buyers wants. Like stated before, the tapers wont really matter in stage 1/2/3 applications.