Does a 3" catback really make any difference over a 2.5"?

[MalcolmV8]

See what I mean by driveshaft access

 

[Gamer2Cars]

Yeah, it's terrible. But hey, if your safety loop doesn't catch it in the event of a failure, your exhaust sure as hell will!

 

[mod mod t56]

I did this on a eaton set up.... custom 2.5 x pipe and Maga flo cat back .... went to a jba shorty flo mater off road x pipe and jba 3 c cat back .... at a 520 hp I lost power it seemed to bog and not as torquey ....same set up but with a whipple....580 @17 and 710 @24 on e85...pulls hard on the top but not real crisp down low .... I think 3" dose not have enough back pressure till u start hitting big boost or high hp

 

[MalcolmV8]

I did this on a eaton set up.... custom 2.5 x pipe and Maga flo cat back .... went to a jba shorty flo mater off road x pipe and jba 3 c cat back .... at a 520 hp I lost power it seemed to bog and not as torquey ....same set up but with a whipple....580 @17 and 710 @24 on e85...pulls hard on the top but not real crisp down low .... I think 3" dose not have enough back pressure till u start hitting big boost or high hp

I would almost guess something else is responsible for your car not feeling real crisp down low. I have 1 7/8 long tubes, 3" o/r X and 3" cat back and can't tell the slightest bit of difference in how it drives down low. Honestly I'd need a dyno and swap between 2.5" X and catback and the 3" to see what the differences are and where each one is better.

 

[Woody6799]

I would almost guess something else is responsible for your car not feeling real crisp down low. I have 1 7/8 long tubes, 3" o/r X and 3" cat back and can't tell the slightest bit of difference in how it drives down low. Honestly I'd need a dyno and swap between 2.5" X and catback and the 3" to see what the differences are and where each one is better.

I did alot of research on this when I bought my Kooks headers and found a bunch of articles relating back pressure and power. Ultimately, I found that 1 7/8 was too much flow for an eaton set up and COULD have negative effects. I eventually went with a 1 5/8 to 2.5 set up which has shown not to be a restriction until the mid 7's, which is more than my set up will ever see.