DrJupeman

Here is the sound of my car with cat bypass and muffler:
Cat Bypass and Muffler

Here is the sound of my car with cat bypass and J-pipe:
Cat Bypass and J Pipe

Frankly, I've not driven the latter on the street yet to let you know how loud it is in real world use. I just thought these two clips might be of interest to folks...

LT1

the second suits me better--then again my chevelle sports a 454 into headers and flowmaster mufflers, no cat and 3" dual exhaust. My 997TT with muff bypasses sounds like a sewing machine next to it.

steaditim

I have the cat-bypass with the muffler and it's still too quiet.
J-pipe is next. Thanks for posting

L8Apex

cat bypass and J-pipe sounds KILLER! I gotta get one! The neighbors would hate me at 5:00am.

Thanks for posting!

DrJ, How did you record this?

DrJupeman

I used my miniDV camcorder and edited out the video to make the clip smaller (KB).

DrJupeman

Btw, the sound is not horrible on the street. The car has a resonance at low (say 2k rpm) but isn't too bad under power. In general it is a raspy, burbling, mean sounding SOB!

straight6

Had the Cat bypass and the j-pipe, and went back to the stock muffler. Couldn't handle that low pitched harmonic on the highway for more than 1/2 hour. The car is too quiet however with the stock muffler. What's the happy medium? Sport muffler?

DrJupeman

Report from those at Mosport this weekend was that my car sounded great and was not too loud from the grandstands. Maybe I can pass the Lime Rock sound police with this setup.... ?

Miles965uk

Thanks for posting that! Sounds sooo much better without both! Ive got the J-Pipe, does anyone think doing the cat bypass add any HP?

Cheers

cobalt

I believe Fabspeed claims 18 to 22 hp increase with the cat bypass and stock muffler in place. You should see less back pressure and heat, Dr J can tell us his feelings best of all.

Dr J,

What about the flames?

DrJupeman

I can't really comment on the difference with a cat bypass vs. not as I've basically only had my car in "healthy" form with the cat bypass. I do not believe the J pipe adds any real noticeable power, but it sounds a lot better and saves ~20 lbs of weight vs. the muffler. The car did feel nice and strong at Mosport this past weekend.

I'm told I had flames at the track. I might need to rig up a camera to see them...

Ian964

I didn't want to install QuickTime player but I final did and wow. The Jpipe+no cat sounds so awesome. If only the idle was a little less it would be perfect.

DrJupeman

Ian, it is about time you succombed to the glory that is Apple Computer. Now go buy yourself an iPod and !

911addict

Have done lots of research on Cat and muffler bypass, and have booked my 965 in for exhaust works in July.
I like the sound of Dr Jupe's 'double' delete, but looking to get a little less base & resonance at low revs. Here's what I have come up wth:

- 100 cell cat (similar sound to cat delete) but road legal (and less flames!)
- Swans neck instead of G-pipe- apparently the length of the pipe gives a nicer sound.
AND after advice from other Rennlisters am also installing a wategate Bypass pipe for those turbo boost moments.

That should give me a bit more 'beef' in low to mid revs, high rev roar, and wastegate scream... and not forgetting some burble on the lift off. That's the theory anyway...we shall see what is the reality.

BTW, with the wastegate bypass work, does it save any labour time to do the 1 bar spring and BOV now, or is it the same to leave that til later?

PS: When all done, will try to post soundclips.

nathanUK '81 930 G50

Doing those two items later on will not take any longer than doing them with that other work at the moment.