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Old 01-09-2002, 04:41 PM   #1
slamck
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Member#: 1436
Join Date: May 2000
Location: Nothern California
Vehicle:
'00 RS
'03 LLBean, '05 B4

Default Help! What causes the cat. converter to break?

I need help figuring out why the catalytic converter breaks prematurely. I broke two cat. converter in 6 months. The guy at the shop speculates of running lean. But I have hard time buying that idea because 00'RS are known to run too rich. Would running too rich kill the cat.?

Any idea would be apprecited.
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Old 01-09-2002, 04:44 PM   #2
Julian
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BRP

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Excess fuel will ruin a cat because the extra fuel will explode (combust) in the cat. We get this normally, that's what the occasional pop is during shifting, etc. But depending on how rich your car is running...

The Sube dealer can scan your ECU to determine short and long term fuel maps. This would be useful in determining whether your car is running lean or rich or neither.

Leaded gas is also a cat killer. Not really available, but still...
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Old 01-09-2002, 04:48 PM   #3
slamck
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Join Date: May 2000
Location: Nothern California
Vehicle:
'00 RS
'03 LLBean, '05 B4

Default info about my car

It's 00'RS with following power mods:
- UR pulley
- Ganz CAI intake with K&N filter
- Cobb spicy cam
- MRT full header exhaust

These are added after the first cat. died 6 months ago:
- Apexi S-AFC
- Apexi S-ITC
- Jumptronic A/F monitor
I added these because I though the car was running too lean and caused the first cat to fail 6 months ago. But what I found was the opposite, the car runs rich at high rpm or high throttle (just like everyone claims).

Now the same thing happened. Can someone help? Replacing cat is expensive, sigh...
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Old 01-09-2002, 04:50 PM   #4
slamck
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Location: Nothern California
Vehicle:
'00 RS
'03 LLBean, '05 B4

Default

I am running premium, 91, gas. I also suspect running too rich. Both cats failed after an extend spirit mountain run. It was fun following a Posche Boxter on a twisty mountain road.
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Old 01-09-2002, 05:05 PM   #5
IggDawg
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a few thoughts:

if you let your car sit and idle for long times it can cause your cats to overheat.

using 91 will generate carbon deposits. it doesn't combust completely in an EJ25, so you may be coating your catalytic surfaces with carbon.

if you let your car warm up in the driveway before dirving it, it can coat the catalytic sufaces with deposits due to the fact that the EGT is too low for the catalyst to do its thing. instead the exhaust gasses just coat the surfaces. if you do some "spirited driving" or an italian tue-up it'll burn this off, but if you jsut limp a short distance and turn the engine off it can damage the cats over time.

running 91 octane will make this last point even worse.

-IggDawg
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Old 01-09-2002, 05:58 PM   #6
slamck
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'00 RS
'03 LLBean, '05 B4

Default

I don't let the car sit and idle much, so that is not likely to be the cause.

The stock cat seems to be able to withstand more abuse than the aftermarket one, cconsidering how rich the car run in stock RS and super rich in WRXs. The first cat failed is the one came with the MRT full header exhaust. And the second one is a Random Tech high flow cat. Anyone has suggestion on what cat I should get this time?
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Old 01-10-2002, 09:28 AM   #7
Patrick Olsen
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1997 Legacy 2.5GT
QuickSilver Metallic

Default

slamck - What do you mean when you say the catalytic converter "broke"? You're the first person with the MRT exhaust that I've heard of having this problem. Have you tried contacting MRT to see if they have anything to say about it? I would definitely be bitching up a storm with them if my brand new cat only lasted a few months.

IggDawg - With the ITC on the car, slamck should be able to advance the timing to take advantage of the higher octane fuel he's using, so I wouldn't think he'd be experiencing the octane-related issues you mentioned. I guess it depends on how well he's tuned the car using his S-AFC and S-ITC.

Pat Olsen
'97 Legacy 2.5GT sedan (with MRT exhaust)

Last edited by Patrick Olsen; 01-10-2002 at 09:34 AM.
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Old 01-11-2002, 02:18 AM   #8
slamck
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'00 RS
'03 LLBean, '05 B4

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Patrick, the piece of catalyst element became loose bouncing around inside the canister. First it was making some funny rattling noise, then it eventually broken into small pieces. See the pic I took:
Attached Images
File Type: jpg 104-0439_img2.jpg (34.4 KB, 110 views)
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Old 01-11-2002, 02:34 AM   #9
slamck
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Join Date: May 2000
Location: Nothern California
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'00 RS
'03 LLBean, '05 B4

Default

I tuned both the ITC and AFC very mildly. Timing advance on the ITC is very gradual 2degree @2400rpm, 4degree @4000, 7degree @5600 and 10degree @7000RPM. The AFC is set to -3% @4000rpm to 8% @5500rpm and up at hi-throttle. I should be able to dial in more feul trim on the AFC, but I feel more comfortable staying on the safe side.

The previous picture is the original MRT cat with the catalyst inside sitting loose. I have not taken off the exhaust again to confirm if the Random Tech cat is doing the same thing. But from the rattling sound coming from underneath the car, I am pretty sure that's what haapens.

Could excessive vibration causes the thing inside the cat to come loose? My wife always complains how rough my RS rides
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Old 01-11-2002, 02:40 AM   #10
slamck
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Join Date: May 2000
Location: Nothern California
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'00 RS
'03 LLBean, '05 B4

Default

One more thing that maybe related... There was massive exhaust leak with the MRT header on the #3 cylinder exhaust port (the rear passenger side exhaust port) and I fixed it by stacking 2 gasket together with good dose of orange hi-temp silicone. If the leak is not sealed 100%, would that cause the cat to break prematurely?

One more speculation with no answer...
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Old 01-11-2002, 08:39 AM   #11
Patrick Olsen
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Location: Where the Navy sends me...
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1997 Legacy 2.5GT
QuickSilver Metallic

Default

I wouldn't think the massive exhaust leak would cause a cat failure like that, but I honestly don't know the answer. Try calling Random Tech and see what they think. I would think they'd want to find out why one of their cats seems to be failing structurally within only a few months.

I would be inclined to think that the catalyst bed is fracturing due to some sort of shock or vibration. Maybe some of those Cusco or Kartboy exhaust hangers would help? Just guessing...

Pat
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Old 01-23-2002, 02:55 AM   #12
slamck
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Location: Nothern California
Vehicle:
'00 RS
'03 LLBean, '05 B4

Default My car was running lean

I finally took my car to the shop, which installed the random tech hi-flow cat in my car 6 months ago. The cat is broken into two pieces, in a way similar to the original cat came with the MRT exhaust. I spotted that the Fram oil filter's rubber grippy coating facing the header was burnt and turned charcoal. The oil filter sits just a few inches away from the passenger side header. This makes me believe extremely high egt cooked the oil filter inches away from the exhaust port and killed the cat downstream. This implies my car is running lean at certain condition. I've read some posts about stock fuel system only capable of supporting certain hp. Could I be hitting the fuel limit with all the NA mod I have?
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