Tom Sharpes

I have a Stainless Steel Cat Bypass pipe for a 964 C2 or 4 that was put on for a test and removed after about 4 hours. I'll let it go for $200.

Email me at team5150@mediaone.net

Ade - C4 91

Hi Tom,

Just for interest, why did you remove it?

Ade
91 C4

Tom Sharpes

I was trying different exhaust setups and when all was said and done I didn't want to temp fate with the CA smog police.

If you don't have a problem with that in your state then it is a great way to free up the exhaust. It sounds nice too !

Randall G.

Hi Tom,

During your experimentation, did you try any after-market headers?

Thanks ...

Tom Sharpes

I didn't go as far as the headers. I tried different combinations of the pipes. Primary and secondary alone and each with the cat bypass.
I settled on the primary bypass alone and decided I didn't want to mess with the smog cops over the cat bypass although it sounded great with the primary and the cat bypass - just a little louder than the muffler bypass alone.
I can't say if there were any real gains in actual performance. My calibrated "BUTTDYNO" says yes because the acceleration was much better with the two bypass pipes on over just the muffler bypass or stock setup.

Randall G.

Thanks for the info, Tom.

The reason I asked .... I have given "casual" consideration to putting headers on my car. Seems like most (all?) of the header systems I've seen involve cat-bypass (not good for us Californians) or dual exhaust (need a hole in your left-rear valence panel).

Must confess that I haven't researched the subject thoroughly. I imagine someone makes headers that are bolt-on (hopefully improved) replacements for the stock units.

Jeff Curtis

FYI, you will find that most, if not all header manufacturers will not be able to incorporate your catalytic converter. The basic design of a header would include a half way decent attempt at making all of the pipes equal length and will require a two-inlet muffler...number of outlets is an option - one or two. If any of you have seen a B&B setup on an SC or Carrera ('84-'89)...a 964 setup would be VERY similar. I am about to bolt on a Fabspeed stainless performance muffler w/one outlet. This effectively replaces the primary and deletes the secondary muffler, it mounts in the original location of the primary muffler and seems slightly heavier than the original primary muffler...but weighs @14lbs less than the primary/secondary muffler combined...also about a 12-14hp gain, supposedly. We'll see, I'll post my "butt-dyno" results!

Randall G.

Hi Jeff,

Thanks for the great information. So, it wasn't my imagination that most (all?) of the header systems I've seen before were either dual exhaust or bypass the cat.

Incidentally, I had an opportunity to install the 993's dual exhaust with my 993 engine. A few complications, though. First, and most significantly, the 993 mufflers won't fit in the 964's narrower rear fenders. So, I would have needed to locate some sort of (narrower) mufflers that fit. Or, maybe do some fancy piping to run the 993 headers to a single muffler. Second, would have needed to install a new left-rear valence panel to accommodate the second exhaust tip. Finally, the mechanic installing the engine gave me the impression that using the 993 exhaust system involved more complications than just the two already mentioned. So, we went ahead and used the 964's exhaust system. Kinda' glad we did, because the car now works and sounds great--just like it used to. If we had pursued the 993 exhaust option, who knows what sort of funky sound we would have wound up with?