I notice axle-backs are cheaper, but it seems like the only difference is that cat-backs have an extra pipe. What‘s the difference in performane?
The difference in performance could depend on the brand of product you use. The axle back as you refer to it I would assume comes with the muffler and goes from there to the rear over the axle. The cat back goes from the cat to the rear so the only real difference you have is the extra section of pipe between the cat and the muffler. None of it will help much if your pre cat situation (from the manifolds to the cat) is all choked off, like say on a v-10 ford. The pipe exits the manifolds and makes a couple of 180 degree bends before coming together into one pipe which is still to small in diameter then enters the cat(s) and gets choked off a little more before it enters the baffled and chambered muffler. You will have different results on different cars. If you are talking about a cat back on a Honda you might be going from a 1 7/8 pipe to a 2 1/4 pipe and an open muffler, you might gain 2 hp and make it really loud and annoying sounding. If you are talking a Dodge 24 valve cummins turbo diesel a larger 4 or 5 inch intermediate pipe with an open 4 or 5 inch muffler and a 5 inch mandrel bent tailpipe might gain you 10 hp. If you add the 4 inch turbo down pipe you might gain 15 hp overall. If you are talking a run of the mill small block emissions legal car with a single exhaust system, from the cat back with a larger intermediate pipe, larger performance muffler like a dynomax ultraflow welded single 3 inch inlet and dual 2 1/2 inch outlets and exit out the rear with duals mandrel bent of course you might notice a substantial difference in hp, sound and fuel mileage. If you take the same car and just replace the muffler with say a 40 series Flowmaster and add dual tailpipes you will notice a little better sound but probably no real hp increase. There is no replacement for spending a little extra money.
The difference in performance between axle-back and cat-back setup varies between manufacturers, but most of the time the difference is very small. Most of your improvement will come from the lower-restriction muffler or mufflers in the axle-back part of the systems. You can get information on what differences, if any, exist between thestock and aftermarket intermediate pipe (the part between the cats and the mufflers) from the tech departments of the various exhaust system manufacturers. Almost all of the reputable companies will have 1-800 numbers providing tech support personnel who can answer your questions.
None. Depends upon the condition of the pipe. If the pipe is well rusted, go cat-back. If not, axle-back will do.
