etom

I did a search to get info about possibly getting a cat by-pass for a stock 92 C2. There is WAY too much info, and some of it seems contradictory or at least controversial. What I am looking for is a little better sound, a little better performance, and, of course, reliability. My questions for you experts, especially for you who have had experience with adding JUST a cat by-pass (I am in North America):

1) Is there a better sound by adding just a cat by-pass?
2) Is there any performance gain?
3) Are there any potential reliability or technical issues?
4) What brands are recommended? (Fabspeed gets most press.)
5) Or should go for an air-intake mod?

Thanks for any responses.

jdodson

I installed a Fabspeed cat by pass last January. The sound is a bit throatier - real nice - not overwhelming. At the time I had alot of other work done to the car which improved performance, but I can't attribute the improvement to the by pass alone. I am unaware of any technical issues other than the need to get past the periodic emmissions test without it. I have to face that in the next two weeks. I'm told by my mechanic that a well tuned 964 engine will run clean enough to pass the emissions test without the catalytic converter - let's hope!
Have no comments on 4 and 5.

Jim

andrew911

I don't see how a car can pass US emissions standards for cars produced in the 1990's without a cat. I have enough trouble getting my fuel injected 1978 VW to get though with non cat (non equipped with one from new), but it only has to meet 1978 standards. Hopefully you didn't throw the old cats away...someone should fabricate an undercar lever that can bypass the cats for all driving except to and from the inspection station

joey bagadonuts

Tough to answer some of these questions because, like most people I bypassed one of the mufflers BEFORE taking off the cat but I'll give it a shot.

1) Is there a better sound by adding just a cat by-pass? IT'S BOOMIER
2) Is there any performance gain? SOME BUT NOTHING AMAZING
3) Are there any potential reliability or technical issues? NO
4) What brands are recommended? (Fabspeed gets most press.) IT'S JUST A PIPE
5) Or should go for an air-intake mod? DO THAT, TOO!

I think the g-pipe and some sort of cone intake are nice enthusiasts' mods and you can feel and hear a difference. If you want to be absolutely sure about the gains, get your car on a dyno before and after the upgrades. I'm sure everyone, here, would love to know the actual difference.

Enjoy!

garrett376

Another thing about a cat bypass: if you have never owned an older car, when you bypass the catalytic converter, your car will stink like an old 911 as it's getting warmed up. Ahhh, unfiltered emissions

For a road-going car, it seems more logical, and less of a pain in the rear to keep the cat and just bypass the mufflers if you're looking for increased noise. Each muffler sounds different - only a G-pipe has a different lower grunt noise than using only a primary bypass which has a more musical low sound that is louder. On a street car, that's really what it comes down to - increasing noise to your taste. Afterall, you're not able to floor it all that often on street roads to notice an extra 10-15HP... get a supercharger, then you'll really notice a difference, or leave your 150-200lb passenger at home!

911addict

On my turbo the cat bypass (by Scart) made a BIG difference to low end response. Probably not as dramatic on a NA.
And the noise is a subtle difference... nicer.
Here's a video link of mine: http://media.putfile.com/TurboScart2

I'm sure quality will vary from maker to maker.

kgorman

I have a secondary bypass, with Fabspeed cat bypass, airbox drilled and snorkel removed, and no undertray. My engine sounds like a WWII fighter plane I tell you! I love it.

In terms of performance, I am sure I gained a few hp. But not massive. I lost lots of weight, so that increases performance in a much more desirable way (accel. and braking and handling).

The Fabspeed folks made a point of saying that the cat bypass they sell is not just a 'pipe'. it's engineered in such a way not to eliminate all backpressure. I am a bit skeptical of that, but I love the part, and while expensive, it's first rate.

Heirsh

my experiences

1) minimal
2) Yeah I think I felt some. Nothing stupendous
3) Dont think so, except that the ox sensor wont stay as hot, so it might not last as long.
4) I have a fabspeed. Fit was perfect. Its not just a pipe. Not that a plain pipe wouldnt be ok, but if you look inside the fabspeed it looks more like a mini muffler than a pipe.
5) if you aer looking for sound messing with the intake will give it to you. if you are looking for performance who knows. Lots of contradictory info out there.