ok i was under my car today and had some time. i was sitting there thinking, a cat back is one pipe, muffler, and the outlets that go out of the muffler to the back of the car. how can this possibly give more horsepower? why not just a muffler? i mean i know how 3" is bigger then the 2.5 but how is it that big of difference. the muffler i'm sure doesn't add 10hp. i'm getting hooker cat back, or i was thinking just a muffler, but how much extra would i get just by that one piece of pipe? thanks

 

i have an 84 TA with a 3 in pipe and if u look at where the pipe goes over the rear axle u'll see that it looks bunched up from bending it and WILL restrict air flow, mandrel-bent tubing is better and with the muffler it depends on how restrictive it is.

also, opening up your exhaust by getting 3 in pipes is always a good thing

 

3" is about 1.5 times larger in area than the 2.5" so it makes a difference. Also how the pipe is made (welds, bends, connections) also affects how it performs.

David

 

For one, the stock I pipe is not mandrel bent, meaning it will have dents in it interfering with flow, where as aftermarket cat-backs are mandrel bent.

 

so how much extra hp are you actually getting stock v.s. catback v.s. just muffler?