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Old 09-27-2010, 05:28 PM   #1
subacoupe
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Question Just Cant Figure it out..

Car: 00 Impreza 2.5Rs

Hey everyone. I have a huge problem I've been sourcing for a while. In the past eight months I've had 3 cats melt down. I have an Ingen CAI, Perrin drive pulley, UEL exhaust manifold, 2.25 all thru, stromung mid section and axle back. New fuel filter, plugs, wires, pcv, cleaned air filter. new front and rear 02's with rear 02 in cheater valve for bugging p0420.

The cats have been mounted right under the transmission cross member at the hump on the passengers side right after the elbow coming off the exhaust manifold. Could it be to close to the front and need to move down stream more at the mid section? The cats have been discoloring on the bottom to a burnt steel look. The insides are chingalinging around. The last one clogged and bogged the motor way down so i had to change plugs after that one.

Any insight appreciated.

Thanks
SubaCoupe
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Last edited by subacoupe; 09-27-2010 at 05:32 PM. Reason: adding year and model
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Old 09-27-2010, 05:54 PM   #2
chazly413
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How is your air/fuel looking? I know lean burns very hot, but I would have no idea if it could do this kind of damage.
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Old 09-27-2010, 06:00 PM   #3
Storm
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Any codes? Severely retarded timing will make the exhaust temps shoot through the roof.....

Jay
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Old 09-27-2010, 06:11 PM   #4
subacoupe
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no codes at all that's why I'm dumbfounded. Everybody seems to blame the mods and say make it stock but that's not why i own a subie. Air/Fuel i would have to assume is off since the only way I'm doing this damage is having raw fuel dump into the exhaust.
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Old 09-27-2010, 06:13 PM   #5
subacoupe
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By the way the car seems to be running ok under drive.. I get roughly 230miles to the tank of fuel no matter how i drive.
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Old 09-28-2010, 01:00 AM   #6
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Have you looked at the CAI (re: the CAI/SRI sticky at the of this forum)?
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Old 09-28-2010, 01:33 AM   #7
Tim Sanderson
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230 miles to the tank is really low. sounds like your dumping fuel into the cat and roasting it. i'd try an injector cleaner. might want ot look for a low budget air fuel meter/guage.
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Old 09-28-2010, 12:28 PM   #8
rexburg22re
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Things to double check;
What brand cat(s)? Is it the right one for your set up? Not all cats are the same.
Have you used a scan tool to check for codes or are you assuming no codes because the MIL isn't on? Could a previous owner have disconnected the MIL?
If you have a scan tool, plug it in while driving and view live stream data. You might have gotten a bad o2 sensor out of the box, what brand are they?
Sounds like the computer thinks it's running lean so it's putting in more fuel, could be just inside the parameters for the MIL to come on but still causing enough to damage the cat.
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Old 09-28-2010, 12:40 PM   #9
RaineMan
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Quote:
Originally Posted by Tim Sanderson View Post
230 miles to the tank is really low. sounds like your dumping fuel into the cat and roasting it. i'd try an injector cleaner. might want ot look for a low budget air fuel meter/guage.
Yep... you are running rich and the excess unburnt fuel in the exhaust is killing the cat.
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Old 09-28-2010, 02:24 PM   #10
formula91
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And this is why you measure MPG by the gallon and not tank.

Something is causing your fueling to be amiss, first two guesses are the MAP and front O2, which I would assume has gone bad too if it's that rich.
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Old 09-28-2010, 03:03 PM   #11
kewlboxer2
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I have the same mods as OP, for the exception of the injen cai. Mine is a hybrid intake. I get about 220 to 260 per 10 gallons.
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Old 09-28-2010, 04:24 PM   #12
formula91
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Quote:
Originally Posted by kewlboxer2 View Post
I have the same mods as OP, for the exception of the injen cai. Mine is a hybrid intake. I get about 220 to 260 per 10 gallons.
That car also runs using the MAP sensor and is like 600 lbs lighter, so something is off for sure.
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Old 09-29-2010, 06:23 PM   #13
subacoupe
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Hey all thanks for the responses.. My 02 sensors are bosch and are under warranty at the autozone. I was also reading that i could have a fuel injector leak down not sure. I do not have a scan tool just a ob2 code scanner. The mil is not disabled i do get the p0420 code a bunch and just reset. I read it comes on in my particular setup with the UEL exhaust Manifold. I used a large core Mangaflow High flow catalytic converter twice and the last one was a Vibrant Performance High flow smaller core converter this previous time around. I have no idea what converter to use at this point. Stock banana pipe is not an option as it is to small for my setup. Any body in here responding got a spare MAP laying around? Where should i start? I know I need to get the fuel problem fixed first before i dump more money in a Converter since they don't warranty meltdowns and I'll just damage the new converter.
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Old 09-29-2010, 10:11 PM   #14
subacoupe
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Quote:
Originally Posted by renyo View Post
Have you looked at the CAI (re: the CAI/SRI sticky at the of this forum)?

Why yes I have and since I have a MAP and not a MAF it does not apply to my model year.
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Old 09-30-2010, 03:23 AM   #15
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Yeah, I realized that when formula91 made his last post, but since no one said anything about it I figured I'd just leave it.
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Old 09-30-2010, 04:50 AM   #16
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If your tank is 15.9 gallons like mine, you are running SUPER rich. I was making ~400 miles between fill-ups stock. Now, with full catless exhaust, CAI, and cams, I am getting ~300 miles per tank. That translates to a change from ~28 mpg to ~22 mpg. I can smell raw fuel in my exhaust, so I know I'm running rich as hell. If you're getting worse mileage than me in a lighter car, something is wrong.

If your tank is smaller than mine, ignore everything I said, and I'll go eff myself

Last edited by bigrobwoot; 09-30-2010 at 04:55 AM.
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Old 09-30-2010, 09:35 AM   #17
subacoupe
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Quote:
Originally Posted by bigrobwoot View Post
If your tank is 15.9 gallons like mine, you are running SUPER rich. I was making ~400 miles between fill-ups stock. Now, with full catless exhaust, CAI, and cams, I am getting ~300 miles per tank. That translates to a change from ~28 mpg to ~22 mpg. I can smell raw fuel in my exhaust, so I know I'm running rich as hell. If you're getting worse mileage than me in a lighter car, something is wrong.

If your tank is smaller than mine, ignore everything I said, and I'll go eff myself

lol well ya better go eff yourself since in my00 its around 14 gal maybe a little less
hahahaa
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Old 09-30-2010, 10:57 AM   #18
chazly413
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It's all about the MPG numbers, how many miles you get out of a tank is not applicable to tanks of different volumes.
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