exhaust question?

[1994SubaruSVX]

i got a friend who is installing either a cat-back exhaust or a high performance muffler. i always, for what ever reason, thought cat-back meant that the customer would get a new catalytic converter, the pipe, and the muffler. if you only get some pipe and a muffler, how could this really be that much more efficient than just a muffler. surely the pipes could not be that inefficient? anyone with some insight on this?:confused:

[Aredubjay]

Cat back simply means FROM that catalitic converters back. In other words, it does not include the cats. As far as efficiency, I haven't read anything in Road and Track or seen any good brochures on the subject lately, so, I can't comment. :D

[1994SubaruSVX]

can not be that more efficient than a hi-flow muffler?

[nvrmore100]

Well........

Correct me if I'm wrong...but backpressure makes a big difference on smaller displacement engines.

I agree a free flowing muffler would give much less restriction...but still not compared to a larger pipe/muffler combo deal. I don't really know how it would affect something a large as a 3.3L, however it makes a significant difference with smaller engines.

One really good example of this is with old VW's (ie, rabbit/golf's, scirroco's, jetta's). I used to rally/slalom race these for fun....I've gone through the whole cat back vs muffler fiasco. First off buying the same muffler (from the full cat back system) and having it installed, much nicer than stock. HOWEVER, later thinking... "Wow if that made that much of a difference...maybe I should get the full cat-back!" I kicked myself in the ass after doing that one (remember...same muffler...just larger pipe from the cat back). I had all kinds of issues after that. Backfiring, extremely low torque, etc. Only advantage was that last 500rpm's before red line was real fun. Needless to say I bought a different muffler and but that system on my rally jetta.

Ryan

[1994SubaruSVX]

this guys has a pt cruiser which has a 2in exhaust pipe. the cat back exhaust they offer is only 2 and a quarter inches. the damn thing retails for $500, i just dont think it is worth. he is not going to get any recognizable gain, especially from 0-60. maybe he will detect some gain at highway speeds. correct me if i am wrong but i think he would get nearly identical gains from just a high flow muffler.

[nvrmore100]

A change from 2" to 2 1/4" on that vehicle will no difference at all. One thing to keep in mind is the nature of what "kind" of performance gain he will get. Remember that free flowing exhaust actually hinder performance off the line, however makes gains in the top end. On a car like a PT cruiser which I would guess doesn't rev very high (I could be wrong...never been in one), this kind of mod may actually make the vehicle perform worse. Unless he is someone you likes to take it to red all the time...he might not be happy with it. Especially for over $500!

Just my 2 cents.

[1994SubaruSVX]

that is what i told the guy. i just wanted to make sure i knew what i was saying. i like to get some back up sometimes you know?:D