rickjaffe

for theoretical discussion purposes only, and understood that it's not necessarily legal, suppose the cat converters fall off a 928, what would you expect to see in terms of hp, noise and smell, stock or with an RMB or cross pipes?

maybe it's more than theoretical, and not completely non-legal since I recall seeing that some of the cross pipes have an option for temporarily removing cats, I presume for racing?

F451

danglerb?

icsmike

oh no......

heinrich

LOL Ed .... yeah you have a point

Jim bailey - 928 International

No Rick is Rick trust me on this one !

the flyin' scotsman

My cat fell off the deck once...............don't remember a smell but it sure got loud.

heinrich

Rick, there are hordes of info on this topic .... just search for x-pipe

F451

I know, just busting ***** here. I couldn't resist.

Rick,

I really can't answer your questions, but perhaps some of the guys with the cats removed can chime in with some real data.

Ed

the flyin' scotsman

ok.............seriously, I fitted the Motorsport X sans cats to stock headers, stock small resonators and a RMB. The engine was freed beyond believe and I suspect my OEM cats wer somewhat plugged. Noise level was intially great but became loud with much resonance at around hwy speeds.

I then experimented with removing the RMB and refitting the OEM rear muffler but I found that to quiet and ugly so I eventually bought a newer GT style rear muffler which IMHO has better looks and sound quality.

rickjaffe

sorry to dredge this up again. read some of the previous threads. looks like rmb or x pipe, not both. don't want to **** off the neighbors. cats don't seem to make that much of a difference, as long as they're not blocked.

thanks,
danglerb
(back at you)

I am who I am.

MGW-Fla

in what way do they not make much of a difference??

ErnestSw

I've dynoed the GT with and without the high flow cats provided with the motorsport X pipe and found no difference whatsoever. I can't speak to the stock cats' effect on HP.

Daniel Dudley

Good gains for any Porsche made before the nineties. Disconnecting the smog pump and AC will also make a difference. Buy a proven system. BTW, there are performance cat systems out there for the buying, so performance doesn't have to hurt emmissions.


Do you have a 928 ? What kind ? Pics. ?

killav

My cats fell off, along with the air pump (darn my luck) last summer. I fabricated my own RMB in place of my rear muffler. I have an 87 S4, so I have the large resonators. The sound was still slightly too loud with no cats (I temporarily welded on a straight piece of pipe), but not too bad in my opinion. So, I welded on some short glasspacks in place of the cats, and the sound is just right to me. I really didn't notice a huge improvement in acceleration by all of this changing around. The glasspacks are probalby negating any gain from losing the cats. The main reason I put them on was for not only sound reduction, but I painted them black and they look like cats. I passed my state inspection recently with no problems (visual, no sniffer here yet).

Big Dave

Without cats (using x-pipe) and keeping the rest of the stock exhaust system on my '85, the sound is louder, the power is improved (seat-of-the-pants-dyno), and the smell is stronger. I may have a fuel mixture issue to resolve, but folks driving behind me have commented once or twice about the schoolbus-like aroma. I like the sound and power and don't mind the smell.

Here's a link to a sound clip...I kept engine rpm at or below 4K