Jump to content
SAU Community

Recommended Posts

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

Link to comment
https://www.sau.com.au/forums/topic/176428-collapsed-metalcat/
Share on other sites

  • Replies 52
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Posted Images

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 by Adriano

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.

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.

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*...

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.

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.

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.

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

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

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Latest Posts

    • As discussed in the previous post, the bushes in the 110 needed replacing. I took this opportunity to replace the castor bushes, the front lower control arm, lower the car and get the alignment dialled in with new tyres. I took it down to Alignment Motorsports on the GC to get this work done and also get more out of the Shockworks as I felt like I wasn't getting the full use out of them.  To cut a very long story short, it ended up being the case the passenger side castor arm wouldn't accept the brand new bush as the sleeve had worn badly enough to the point you could push the new bush in by hand and completely through. Trying a pair of TRD bushes didn't fix the issue either (I had originally gone with Hardrace bushes). We needed to urgently source another castor arm, and thankfully this was sourced and the guys at the shop worked on my car until 7pm on a Saturday to get everything done. The car rides a lot nicer now with the suspension dialled in properly. Lowered the car a little as well to suit the lower profile front tyres, and just bring the car down generally. Eternally thankful for the guys down at the shop to get the car sorted, we both pulled big favours from our contacts to get it done on the Saturday.  Also plugged in the new Stedi foglights into the S15, and even from a quick test in the garage I'm keen to see how they look out on the road. I had some concerns about the length of the LED body and whether it'd fit in the foglight housing but it's fine.  I've got a small window coming up next month where I'll likely get a little paint work done on the 110 to remove the rear wing, add a boot wing and roof wing, get the side skirt fixed up and colour match the little panel on the tail lights so that I can install some badges that I've kept in storage. I'm also tempted to put in a new pair of headlights on the 110.  Until then, here's some more pictures from Easter this year. 
    • I would put a fuel pressure gauge between the filter and the fuel rail, see if it's maintaining good fuel pressure at idle going up to the point when it stalls. Do you see any strange behavior in commanded fuel leading up to the point when it stalls? You might have to start going through the service manual and doing a long list of sensor tests if it's not the fuel system for whatever reason.
    • Hi,  Just joined the forum so I could share my "fix" of this problem. Might be of use to someone. Had the same hunting at idle issue on my V36 with VQ35HR engine after swapping the engine because the original one got overheated.  While changing the engine I made the mistake of cleaning the throttle bodies and tried all the tricks i could find to do a throttle relearn with no luck. Gave in and took it to a shop and they couldn't sort it. Then took it to my local Nissan dealership and they couldn't get it to idle properly. They said I'd need to replace the throttle bodies and the ecu probably costing more than the car is worth. So I had the idea of replacing the carbon I cleaned out with a thin layer of super glue and it's back to normal idle now. Bit rough but saved the car from the wreckers 🤣
    • After my last update, I went ahead with cleaning and restoring the entire fuel system. This included removing the tank and cleaning it with the Beyond Balistics solution, power washing it multiple times, drying it thoroughly, rinsing with IPA, drying again with heat gun and compressed air. Also, cleaning out the lines, fuel rail, and replacing the fuel pump with an OEM-style one. During the cleaning process, I replaced several hoses - including the breather hose on the fuel tank, which turned out to be the cause of the earlier fuel leak. This is what the old fuel filter looked like: Fuel tank before cleaning: Dirty Fuel Tank.mp4   Fuel tank after cleaning (some staining remains): Clean Fuel Tank.mp4 Both the OEM 270cc and new DeatschWerks 550cc injectors were cleaned professionally by a shop. Before reassembling everything, I tested the fuel flow by running the pump output into a container at the fuel filter location - flow looked good. I then fitted the new fuel filter and reassembled the rest of the system. Fuel Flow Test.mp4 Test 1 - 550cc injectors Ran the new fuel pump with its supplied diagonal strainer (different from OEM’s flat strainer) and my 550cc injectors using the same resized-injector map I had successfully used before. At first, it idled roughly and stalled when I applied throttle. Checked the spark plugs and found that they were fouled with carbon (likely from the earlier overly rich running when the injectors were clogged). After cleaning the plugs, the car started fine. However, it would only idle for 30–60 seconds before stalling, and while driving it would feel like a “fuel cut” after a few seconds - though it wouldn’t fully stall. Test 2 – Strainer swap Suspecting the diagonal strainer might not be reaching the tank bottom, I swapped it for the original flat strainer and filled the tank with ~45L of fuel. The issue persisted exactly the same. Test 3 – OEM injectors To eliminate tuning variables, I reinstalled the OEM 270cc injectors and reverted to the original map. Cleaned the spark plugs again just in-case. The stalling and “fuel cut” still remained.   At this stage, I suspect an intermittent power or connection fault at the fuel pump hanger, caused during the cleaning process. This has led me to look into getting Frenchy’s fuel hanger and replacing the unit entirely. TL;DR: Cleaned and restored the fuel system (tank, lines, rail, pump). Tested 550cc injectors with the same resized-injector map as before, but the car stalls at idle and experiences what feels like “fuel cut” after a few seconds of driving. Swapped back to OEM injectors with original map to rule out tuning, but the issue persists. Now suspecting an intermittent power or connection fault at the fuel pump hanger, possibly cause by the cleaning process.  
×
×
  • Create New...