Fried my Cats ...
Thread Starter
Safety Car
Joined: Mar 2002
Posts: 4,928
Likes: 1
Cruise-In V Veteran
St. Jude Donor '09
Fried my Cats ...
Trying to setup/tune new cam with Edit. Made some changes ,warmed her up, and headed out for a 15- 20 min run to do some logging. Ran the best ,yet. Stopped in my bud's driveway (JLSRU75) and discussed what we still needed to correct/change. Luckily EFILive is still logging.In the middle of the discussion I ran her up to 4 grand to see how lean it was (wideband O2 and LTFTs) then continue discussion. Pull in the garage and I smell something burning. JLSRU75 checks under car -"Here it is !"
The CATS were glowing cherry-red. You could not put your hand between the seats and tunnel - it would burn.We used wet rags between the seats and tunnel, turned on a big shop fan and waited . Eventually we hosed them down.
What happened? Here is what we think happened . EFILive shows the entire time we sat in the driveay ,at idle, the PCM was pulling fuel (-12.5 both banks). The only time it went positive (LTFT) was when I ran it up to 4 Grand - was an excellent marker.
So the motor was running very rich as we sat in the driveway and this fed the cats. The result was the heat of combustion and increased tunnel temps.
I now have a very muffled exhaust note - cats are fried (melted ceramic core). So I'll go to Off-Road pipes and scratch the cats( no pun intended).
I have long tube headers and no rear O2 sensors. I assume the rear O2s are needed to calculate cat temps ( I know it's a calculated parameter). I did not go into Cat Overtemp (PCM),that I know of, and there are no codes.
If any of you Guys have any info please chime in. Guru's???
:yesnod: :yesnod: :yesnod:
The CATS were glowing cherry-red. You could not put your hand between the seats and tunnel - it would burn.We used wet rags between the seats and tunnel, turned on a big shop fan and waited . Eventually we hosed them down.
What happened? Here is what we think happened . EFILive shows the entire time we sat in the driveay ,at idle, the PCM was pulling fuel (-12.5 both banks). The only time it went positive (LTFT) was when I ran it up to 4 Grand - was an excellent marker.
So the motor was running very rich as we sat in the driveway and this fed the cats. The result was the heat of combustion and increased tunnel temps.
I now have a very muffled exhaust note - cats are fried (melted ceramic core). So I'll go to Off-Road pipes and scratch the cats( no pun intended).
I have long tube headers and no rear O2 sensors. I assume the rear O2s are needed to calculate cat temps ( I know it's a calculated parameter). I did not go into Cat Overtemp (PCM),that I know of, and there are no codes.
If any of you Guys have any info please chime in. Guru's???
:yesnod: :yesnod: :yesnod:
Burning Brakes
Joined: Mar 2003
Posts: 1,171
Likes: 1
From: South Lyon MI
Re: Fried my Cats ... (c5chris)
Cut those suckers out and have your tuner shut off the rear O2 sensors, You will have to tolerate the smell but it might even give you some additional power
Race Director
Joined: Aug 2002
Posts: 16,699
Likes: 1
From: Redacted
Re: Fried my Cats ... (binksZ06)
the motor was running very rich as we sat in the driveway and this fed the cats.
You gotta really watch that when you are doing major changes. (speculation on my part follows) Aggresive cams can have a lot cylinder scavenging, which can push a lot of unburned stuff out the exhaust valve, down to the cats. So even if the mixture is not tecnically "rich" a cam might still blow a lot of fresh fuel down to the cats.
The rear O2's are for compliance afaik. I don't think they are used for anything else in the pcm.
I'm not a guru, but that's what cats do, burn HC before it goes out the tail. If you feed 'em a lot, they'll turn cherry red.
Thread Starter
Safety Car
Joined: Mar 2002
Posts: 4,928
Likes: 1
Cruise-In V Veteran
St. Jude Donor '09
Re: Fried my Cats ... (larrysb)
the motor was running very rich as we sat in the driveway and this fed the cats.
That's exactly what happened.
You gotta really watch that when you are doing major changes. (speculation on my part follows) Aggresive cams can have a lot cylinder scavenging, which can push a lot of unburned stuff out the exhaust valve, down to the cats. So even if the mixture is not tecnically "rich" a cam might still blow a lot of fresh fuel down to the cats.
The rear O2's are for compliance afaik. I don't think they are used for anything else in the pcm.
I'm not a guru, but that's what cats do, burn HC before it goes out the tail. If you feed 'em a lot, they'll turn cherry red.
That's exactly what happened.
You gotta really watch that when you are doing major changes. (speculation on my part follows) Aggresive cams can have a lot cylinder scavenging, which can push a lot of unburned stuff out the exhaust valve, down to the cats. So even if the mixture is not tecnically "rich" a cam might still blow a lot of fresh fuel down to the cats.
The rear O2's are for compliance afaik. I don't think they are used for anything else in the pcm.
I'm not a guru, but that's what cats do, burn HC before it goes out the tail. If you feed 'em a lot, they'll turn cherry red.
Le Mans Master
Joined: Jan 2001
Posts: 5,786
Likes: 6
From: Lafayette Colorado
Re: Fried my Cats ... (binksZ06)
Yup. 239/251 with a 106 LSA :yesnod: ..not exactly efficient at low RPM. :thumbs:
Keith
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Thread Starter
Safety Car
Joined: Mar 2002
Posts: 4,928
Likes: 1
Cruise-In V Veteran
St. Jude Donor '09
Re: Fried my Cats ... (kromberg)
Keith -Idles @ 1250 although set at 1400 in idle table. Any idea why I'm missing 150 RPM? Hmmm- I need to check this.
:yesnod:
eb02z06 - not sure whose they are. Bought from LGM last year along with long tubes.It's not a fault of the cats ...it's I'm a dumba** and toasted them. :lol: :lol: :lol:
:yesnod:
eb02z06 - not sure whose they are. Bought from LGM last year along with long tubes.It's not a fault of the cats ...it's I'm a dumba** and toasted them. :lol: :lol: :lol:
