jody stowitts

Anyone(s) ever replace catalytic converter on car with 97k+ just for "therapeutic" reasons only. Streather book says cats function @ 60-90% efficiency depending on age, "conditions", etc. If so, any increase in power, fuel economy experienced as a consequence of repl.? Car passed emissions test a couple yrs. ago @ 89k. I'm inclined to leave well enough alone; and I'm NOT a "green" fanatic. Just curious only, and with $700+ outlay for new one am easily persuaded to indeed let sleeping dogs lie. Car is '91C2 with close to 98,000mi. Highway mileage driven @ conservative RPMs of 3100-3500 currently yields just a hair under 18mpg. Tune-up is another 4-5k mi. away. Thanx.

Lemass Automotive

cat bypass??

sundog

I've got a few projects, and the cat delete with headers is high on the list.

I felt some butt dyno HP just from removal of the primary muffler, so I would think that removal of the cat would help. But of course there needs to be some back pressure for the system to work properly. The 964 exhaust was really poorly designed however.

jody stowitts

No cat bypass, this a stock, everyday, non-race car.

Laker

If you are passing CA's Smog check as is, let sleeping dogs lie. If you want an increase in performance and don't mind swapping the cat back every year for smog check, a 200 cell race cat or bypass would do the trick

Porsche964FP

From several sources of good authority, the best parts to bypass on a standard exhaust for best performance results is Cat-bypass and G-pipe/ final silencer bypass combination.

Plus the sound is awesome!

ILC32

I have headers that go right into the exhaust (no cat "bypass" because the cat itself is gone) and the sound is amazing.

RSAErick

I'd highly recommend letting sleeping dogs lie. You most likely will not notice any improvements in power or fuel economy. I say this because I did not notice any improvements in either when I removed my cat, with ~100k miles, entirely. A dyno may say otherwise, but any power increases due to better flow through the cat are quite minor. I'd suggest putting the $700 into something else with a better return.

Good luck!

jody stowitts

ILC32: Reckon I'll just let it be. Re: amazing sound. It sounds (no pun) silly, but the only sound that really "turned my head" was the exhaust note on early 911's, i.e. 65-73ish. If you've got a way to replicate that, I'm all ears (no pun).

jody stowitts

RSAErick, (et.al.): Thanks for the info, much obliged!

Shamus964

catless B&B header exhaust

It's the closest soundtrack for a 3.6 and it's amazing. Getting 'that' early snarly sound from these big motors ain't easy

JMHO

993James993

Try a g-pipe. The sound is great. It's an easy install and the
car will pass emissions without any issues.

rollingjack

I changed original cat to 200cel metal cat. I measured exhaust noise by idle with standard and after with new 200cel cat. Standard cat was 76 dbA and with 200cel it was 82 dbA.
Car has cup pipe and second silencer.

Sound:
http://www.youtube.com/watch?v=EG2Sp...ature=youtu.be

g60pops

decat and g pipe/swan neck if you can
http://youtu.be/t8DjihohHho

ILC32

That's what I'm running. It does sound really good, IMHO.