Collapsed Metalcat

[Craney]

About 6 months or so ago i put a high flow 'metal cat (brand name) ' on my r34. After a while i lost performance and after talking with my tuner we found that catalytic converter had collapsed. Seemed a bit strange since metal cat are supposed to be a pretty good brand. So we threw another one in and a couple of months later, same deal. We pulled it out and my tuner contacted the dealer and got a new one from a different batch (dealer seemed to think they might have had a problem batch).

This one was a lot better however it is now starting to show the same symptoms as before.

-blows black smoke as the turbo comes on and throughout most of the rev range there after. Leaves black dots on the rear of my car.

Black smoke is usually a sign that the tune is far too rich but my tuner assures me that is not the case, though the a/f ratio does dip just below 12 for a few hundred revs. One of his ideas is that the exhaust stream is too hot for the cat, which doesn't make too much sense either since i'm only running 14 psi and 250 rwkw (after fresh tune). Another mechanic told me that my silencer is restricting the exhaust too much and could also be doing something there (3.5 inch turbo back exhaust, silencer takes it to about 2-2.5 inch at muffler).

I want to take it to 300 rwkw soon but there's no point until i get this issue dealt with. If anyone has gone through this before or has any idea what's going on your help would be greatly appreciated.

Car:

R34 gt-t

3.5" turbo back exhaust

metalcat hi-flow cat

microtech ecu

600hp turbo (was doing this before turbo install as well however)

650cc sard injectors (as with turbo, was a problem before injector install)

pod filter

600*300*75 hybrid intercooler

running 250rwkw at 14 psi boost

[Adriano]

Another mechanic told me that my silencer is restricting the exhaust too much and could also be doing something there (3.5 inch turbo back exhaust, silencer takes it to about 2-2.5 inch at muffler).

Which is it, 2 inches would be a massive restriction, have you considered fitting an Exhaust temp gauge. If the tuner has to severly retard the timing to prevent detonation, then the EGT's can go through the roof. This would make sense, as the gtt's are renown for having to run low timing to compensate for their different combustion chamber design, and higher comp ratio

How close is the cat to the turbo, could try moving it back a bit.

Edited July 13, 2007 by Adriano

[MANWHORE]

When you say it collapsed the metalcat, you mean it bent in all the metal fins? or it melted them and it welded together?

Or do you just mean that it destroyed the emissions substance on the cat, and thus the black smoke?

Bit ambiguous.

[Craney]

didn't look like it melted or anything. Just seemed like the walls of the honeycomb structure collapsed on themselves. The inlet to it wasn't too bad but the outlet side all collapsed to the center. My tuner seems to think the black smoke is the cat disintegrating as you say. But being on the third one now and it looks like it's doing it again seems strange.

[T04GTR]

no no. its just a china cat. metal cat or x force. there all the same.

metal cats do tend to colaps if they have been overheated. id be claiming waranty

[Craney]

that's the point though. I have received the last two free of charge thx to my tuner, but replacing the cat every three months isn't something i want to be doing. As for being a crappy china cat, if you know of a better brand i'd be happy to hear about it, but as far as i know metal cats are supposed to be the beez neez in australia.

As for temperature collapse, i find it hard to believe since my tuner has them in most of the cars he tunes (some with 400 rwkw+) and I'm the only one with these issues. I'm not rejecting the theory completely and i appreciate the replies but it just seems very weird that the higher power cars don't suffer the same fate.

I'll get the silencer taken out soon and free up the exhaust a bit more and see if that helps i guess.

Any more ideas are still welcome as the issue is frustrating me pretty bad atm.

[Fixxxer]

I'm sure I've read that some of the rotary guys have had similiar issues (rotaries have high EGT's). Maybe check out Ausrotary for some more info.

Fixxxer

[dead32]

my mate's rx2 had a metal cat fitted, colapsed on after about 5-10 drives of the car, blocked his exhaust system up and forced the external gate to open causing boost issue's, my car has identical symptoms to yours although alost less power and rb20, we both share the all and mighty *metal cat*...

[Craney]

righto, well i'm talking to one of the guys at metal cat next week, hopefully we can brainstorm a little and i'll update this thread.

[BAMR33]

I agree with an earlier post, weld the cat in further back it won't see as much heat.

[T04GTR]

it seems these cylindrical cats just kinda fall apart. a busted cat will not make clouds of black smoke under power. i can honestly say its because of the tune.

100 bucks says if you put a standard ecu in it wont do it. etc etc.

its basicly trying to burn off all th unburnt fuel and getting hot for it. ie.. if your crusing on the freeway at 100k for 20 mins the cat shouldnt be red hot. but i rekon yours will be. like my one till i got a "decant" tune.

[arep3]

might i suggest taking out the silencer? i didnt have the same prob as you. Stock standard i was on 154awkw. with pods, dumps/front pipe, cat and full 3" exhaust i was on 120awkw with silencer. after taking it out i jumped to 174awkw. silencers suck. it could be putting too much back pressure and keeping the heat in thus cooking the cat. my 2c.

[LTHLRB]

decat pipe mate, only good way.

[Trust33]

have you got any pics of the collapsed cat?

[rob82]

Catalytic converters dont fail from the back of the car the usually always implode in the middle on the trubo side not the muffler side. I would remove the silencer asap. This definately shouldn't be a warrantable item either!

Note: It's most likely the retarded ignition event killing the cat - what timing number are you running.

[Craney]

At the moment the cat is sitting about midway down the car, thought that'd be enough of a distance. As for pics i'll have to see my tuner to see if he kept any of em. and i'll have to get back to you on the timing.

[kermit]

my guess is the restriction from the muffler as i have seen the same sort of thing ( massive discolouration on the cat body ) on other restricted exhaust systems . to be honest the size your silencer drops down to is insane and your mechanic should have removed it before performing the other performance work on your car .

kermit

Kermit Engineering

[Gazee]

when the metal cat collapses, does it by any chance let off a really strong smell?

[T04GTR]

no it doesnt.

if you car is tuned well it should smell like new carpet.

and the cat colapses from the rear when to much fuel is going thru it. as it burnes hotter at the back. if it colapses at the front its just got to hot or a blockage. hence why the temp sensor is in the rear of the cat on 32/33's

[raz0r$harP.UK]

Speaking to an exhaust place recently, they were telling me of a few stories about these type of cats failing after a while, matrix collapses and causes a blockage.