testing a catalytic converter
 

I am thinking of re-installing the original cat on our 84 Carrera. I removed it 8 years ago and in its place installed a Fabspeed europipe with the oxy sensor bung, and a Steve Wong chip that recognizes the "no cat" condition. It has worked great since installed, but I am weary of the exhaust smell driving around town.

My questions are, "can I test the cat to make sure it's functional and not partially plugged?" It was working when I took it off, so maybe it's still ok. Or does it have to be on the car to test it? Also, will the chip be ok to use with the cat installed? Thanks.

I suggest calling SW for info on the last part of the Q....

and I have no idea how to "test" the cat,...but I doubt it dissolved during its storage, should be just as good as the day it was removed

I'm told my a muffler manufacture that the Cat from an 84 911 should be good for 200 or 300k miles, depending on the running condition of the engine.

Unless you have had varments in there, it should be fine.

They don't deteriorate by lack of use.

Reading your post I couldn't help but focus on your "exhaust smell" comment. Have you had your CO% checked/set? Perhaps you have a different problem such as a rich-running air flow meter that can't be adjusted. Even with a chip your car should not smell like a big block 1967 Camaro!

That said, your cat will still be fine, but if the car is running super-rich (or super-lean) the bad fuel mixture might shorten the cat's life. Get your car over to a good independent and have your CO% checked before you do anything! If necessary, contact Steve and find out what the best CO range is for his chip. Idle speed adjustment and mixture on your car call for a precise procedure, so be sure that the shop is well-versed in tuning 3.2 liter cars!

I apologize for not remembering the specifics but a local exhaust shop tests cats with an infrared thermometer pointed at the exhaust pipe before the cat and after it when at full operating temperature. The exhaust pipe after the cat should be hotter than the pipe entering. What i don't remember is how much hotter but i want to say it was around 100 degrees F.

Thanks all. I will get the CO% checked at a shop here in Charlotte, that is something that has never been done in the 20+ years we've owned the 911. If that cures the smell, I will leave it as is (I haven't busted any knuckles all summer, and would like to stay that way). The car is pushing 97,000 miles so the cat should easily outlast me if they're good for 200K+!
Maybe Steve will chime in on this. Again, thanks.

I hate to point this out...but SOOOO many people point out cars as having "too many owners" and yet having less is not always the answer.

I have thought about those comments and often replied with "new owners take the car in for every noise, they are excited and wanting to tune it up, clean it up and learn..when the car makes a noise they try to solve it...and when long term owners cars do the same thuing they say...it's always done that, it's no big deal"


I am not suggesting you neglect your car.... but the fact that the CO has not been check to the best of your knowledge in 20 years (your words) is very surpising to me (although i suspect your mecahnic has checked it and maybe not told you)

best of luck on fixin up the smell....

Ed, thanks for your comment. Motronic is a system that really doesn't lend itself to a lot of tuning or messing with, it is pretty well foolproof unless something is wrong. The system monitors itself and adjusts the stoichiometric value (14.6 to 14.7) pretty well as far as I know. The car runs great, and always has and gets plugs, etc. and normal maintenance as the book suggests. Checking CO isn't in the maintenance schedule, otherwise it would have been done.
This particular car is a garage queen and doesn't get much use, so other than oil, filters, dry-rotted vacuum hoses, etc. and changing the brake fluid it doesn't need much maintenance.
I happen to think that consistent ownership is generally a plus, and a car that gets a lot of turnover in ownership normally has issues of "previous owner" mods that are often expensive to remedy.SmileWavy

I think you might need to give your car an Italian tune up or two :)
Just sayin ...

Cheers !
Phil