jyoteen

and install the bypass? My cats are making noise again, which is a precursor to failure. If they fail and they will, i'll be looking at a SIXTH set of catalytic convertors during the life of the car thus far.

I'm not going to spend a red cent on a catalytic convertor anymore for this car. I may as well take the current ones off that aren't throwing a code yet and then put them on for smog test, take them off, rinse and repeat.

I don't get what the cause would be....****ty CA gas? Car does not give any other indication of malfunction, no misfires, no 02 sensor faults.

I'm convinced that track duty keeps these guys failing. The setup is not condusive to it I suppose, but I don't understand how others don't have same issue, or the GT3 etc.

logray

Bad O2 sensor causing that bank to dump too much fuel? Plugged or bad fuel injectors?

Or worse stuff, accompanied by a lot of soot probably...

Piston blow-by, bad ring seal, bad valve seal, etc...

Is it always just one cat, or both?

Hardback

There are numerous cat bypass threads you may want to search. Most here feel the bypass pipes are too loud for street use. The monority love them.... I replaced my bad cats with freer flowing 200 cell xpipe. The car has a wicked sound now combined with the PSE.

6 sets of cats is ridiculous... these parts are expensive... Id be frustrated too mate.

soverystout

6 sets of cats? That's insane! And cats are going to continue to get more expensive as the price of precious metals go up. Jeeze.

jyoteen

Well, the issue has existed since my first cat replacement at 24K miles (years and years ago). I replaced the recent set a year ago, and the one before that was at 82k miles (I have 118k now). It's always one of the two cats (left bank).

I'm thinking it's track duty because I bet if I were to go back and see when they failed, it's usually soon after a track event. My thinking is that some sort of vibration is causing cracks in the honeycomb structure due to the high revs instead of a fuel related issue. I just went to a track event and now the cats are making noise. Last year, same thing.

Maybe I should stay away from Laguna Seca? ;-)

Engine was taken apart and new valve seats were installed and there is no indication of 02 failure. I guess there could be piston blow by, but I have no way to remedy that, so I'm thinking of alternatives that doesn't really cause a raucous and invite the po-po anymore than my speed yellow color does already.

I literally have no indication that anything else is malfunctioning like injectors or coil packs. Car runs fine, sans the catalytic convertor issue. And since this issue isn't exactly new, I'm thinking to leave the other systems out of the loop.

philooo

I am with you on this one, my first Cat went dead right after track duty and now I have another one which start to make noise and again it happened right after a DE. I think these cats can't handle wide open throttle.

I am also looking to buy a cat bypass. the hi-flow are quite pricey, so I am more looking into the racing bypass which are relatively cheap.

Phil.

kt

What do bad cats sound like?

I just did my first DE and had the sucker at WOT pretty much the entire time. What a blast!

philooo

mine sound like something is loud clicking/knocking coming from under the rear bumper, scary at first but you will see the knocking sound does not increase when engine rev. If you hold a screwdriver to the cat and put the handle onto your hear you will distinctively hear that the knocking comes from there. If not the knocking is a bit scary as it sounds like it is coming from the engine.

The noise is very strange and I was really not convinced it was the car until the CEL light came up with a bad cat error code on the durametric and dealer validated the problem.

I had my last one changed under warranty and the previous owner also had changed one.

FYI the CEL light can take a while to come up once the cat starts making noise. I think it took me a good 200 miles after hearing the sounds, before the CEL light came up on the dashboard.

jakermc

Yes, track use will kill the cats. I just had one replaced on my street car this morning and the mechanic at the dealership, who races and works almost solely on track oriented cars, confirmed this. Like the posts above, mine failed after tracking the car for the day. It literally failed on the drive home. (Rattling sound, but CEL had not come on yet).

Mechanic said its a heat issue, not a vibration issue. If a cat is nearing failure, going to the track will push it over the edge. BTW, list price on these guys are up to nearly $2,100 for a single cat!!

Sounds like a coffee can full of rocks is being shaken. Scared the crap out of me because I first thought it was the engine. Had to stick my head under there before I figured out it was an exhaust issue and 'only' a bad cat.

I don't think beginners will have an issue, my wife's car has been tracked a few times (she's a green student) and it has 86K on the original cats. But driven hard seems to be another story. I'm not sure I will track my street car again, probably better to stay in the race cars. A real shame, because tracking the Cab was a blast!

Turn3 Autosport

There seems to be some confusion on bypass pipes. MUFFLER bypass pipes are far too loud for street, and most tracks. CAT bypass pipes sound great. We are fond of the Fabspeed X-pipe and run one on our 996 Race car. Well made part that fits great. The sound is only slightly louder but has a more "throaty" growl to it.

We would be happy to work at putting a buy together for these.

Cheers

Ubermensch

Are the 200 cell cats any more resistant to this type of damage?

-Shawn

LC MotorSports

No. Fail just the same and sometime faster.

ivangene

LC MotorSports

That is one Bad Cat.

Quadcammer

Track use is hard on cats because the car runs so rich at WOT. Instead of the usual 14.7 or so a/f ratio at cruising, wot can be as rich as mid 11s in factory form. This extra fuel is great to keep the combustion chamber cool, but it heats the snot out of the cats.