Installed cat bypass pipe today

RazorRacer · 09-21-2002, 04:35 PM

For more horsepower and a cooler running engine, I took out the old cat converter and installed a cat bypass today.

I was hoping to get much more horsepower as the cat converter seemed plugged (see photo). I was also expecting a better sounding engine.

The difference is ever so slight in horse power and sound. I will test the engine temperature at the Nov 16/17 DE in Texas.

Looking at this photo, could the muffler be plugged up with cat guts? I know I'm not getting the full 185 HP out of her.

SK · 09-21-2002, 04:59 PM

What type of bypass did you buy?

RazorRacer · 09-21-2002, 07:16 PM

link to cat bypass

RazorRacer · 09-21-2002, 07:19 PM

Here's a photo...

Nathan M · Nathan M's Garage

I added the same type of cat bypass to my 3.2 and also noticed only a slight increase in power, although it does feel to rev a little more freely at higher rpm. The sound of the car has improved big-time. It now sounds like a Porsche should and although is no noisier at idle or part/medium throttle, get in the gas and it sounds great

I still feel my car isn't giving what it should. Maybe this is a 911 characteristic??!! Deceptively powerful? Comparing mine to my daily driver, which is a 1995 Golf 2.8 VR6 with a factory quoted 174hp, the 911 doesn't feel that special. Need to get the Porsche on a rolling road to see if there's a problem.

expat · 09-22-2002, 01:21 AM

I put the same catbypass on last week. I'd agree there's little feel of power improvement (wasn't really expecting that anyway) but the sound is a little better. I also agree that it seems to rev a lttle freer at higher revs but that could be my wishful thinking.

Cheers
mark

rstoll · 09-22-2002, 04:43 AM

That's not cat guts in the picture. Looks like steel wool. The cat is full of solid ceramic like wafers with tiny holes.

Steve W · Steve W's Garage

That's not really steel wool, but the steel mesh that packs and holds the ceramic honeycomb tight against the outer shell. Looks like some of it has blown out and away from the perimeter.

On a different subject, I used to have a European pre-muffler on my 3.2 and noticed no difference in sound compared to my stock cat, but there was some more power. Here is a part of an email Bruce Anderson sent me in May 2000 on exhausts. Don't shoot me, I'm just the messenger:

Quote:

For some reason the cat bypass doesn't seem to do much if you are going to
use the original heat exchangers and some sort of a sport muffler, you will
need to find a European pre-muffler to run with the combination to get all of
the gain possible. When we did this with the Ruf single inlet, dual outlet
sport muffler we did see a similar gain to what we saw with the SSI heat
exchangers and the pre-muffler and Ruf dual outlet sport muffler combination.
However the output was down a just a little in the mid-rpms (2500 to 4000
rpm) and again at 5500 rpm. At peak horsepower the SSI combination produced a
gain of 12.5 hp while the Ruf sport muffler and pre-muffler produced a gain
of 11.78 hp. In the mid-rpms the SSI combination showed a gain of 4 hp to
6.9, so if you are after all that you can get the SSI combination is the best
way to go. Both systems offered some gains from 2500 rpms up and what I would
consider significant gains. Remember that while these are not great gains
that this was all part of test of chips for the 3.2 Carrera engine in
Excellence magazine and our conclusion was that the best chip was an exhaust
system change. The best of the chips didn't come anywhere near what we
achieved with either of the exhaust system changes.