NOx failure, chipped, which factory LH rev to swap in?
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86.5
Well, new cats were an excuse for a crossover pipe, but they didn't get my sticker. I've read all the other threads at this point on this subject (half of which are NOx failures, half CO or HC, which are both low on both my tests). Since the first failure, I also put on a new O2 sensor (there was no O2 sensor on the thing the first time, to my surprise) and replaced the intake rubber pieces (which were a source of significant vacuum leak) and fixed some charcoal-canister-related vacuum leaks.
The NOx reading actually got worse (3.06 gpm vs. 3.04 average, need 3.00 to pass).
Although there is surely a vacuum leak somewhere to plug (idle 800), I also want to get rid of the Autothority chipset until I pass to reduce the timing advance. Will the '85 fuel mappings (LH rev. 03) vs '86 "more aggressive" (LH rev 04) make me any more likely to get by? I can get either and I only failed by 2%, so a little change in mixture could make a difference.
I'm going to replace the plugs, as well (WR7DC).
The thing's running pretty well, a slight bog off the line but that's not entirely atypical with the early 32V/2.20 (someone with a supercharger will probably suggest that it's quite correctable).
Well, new cats were an excuse for a crossover pipe, but they didn't get my sticker. I've read all the other threads at this point on this subject (half of which are NOx failures, half CO or HC, which are both low on both my tests). Since the first failure, I also put on a new O2 sensor (there was no O2 sensor on the thing the first time, to my surprise) and replaced the intake rubber pieces (which were a source of significant vacuum leak) and fixed some charcoal-canister-related vacuum leaks.
The NOx reading actually got worse (3.06 gpm vs. 3.04 average, need 3.00 to pass).
Although there is surely a vacuum leak somewhere to plug (idle 800), I also want to get rid of the Autothority chipset until I pass to reduce the timing advance. Will the '85 fuel mappings (LH rev. 03) vs '86 "more aggressive" (LH rev 04) make me any more likely to get by? I can get either and I only failed by 2%, so a little change in mixture could make a difference.
I'm going to replace the plugs, as well (WR7DC).
The thing's running pretty well, a slight bog off the line but that's not entirely atypical with the early 32V/2.20 (someone with a supercharger will probably suggest that it's quite correctable).
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NOx is is produced when the combustion temperatures are high, which is usually an indication of a lean mixture. With your slight bog I would think this is the case. I think you are on the right track with th air leak.
Good Luck.
Good Luck.
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Originally Posted by a4sfed928
NOx is is produced when the combustion temperatures are high, which is usually an indication of a lean mixture. With your slight bog I would think this is the case. I think you are on the right track with th air leak.
Good Luck.
Good Luck.
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Shane? What are the HC and CO numbers?
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Originally Posted by worf928
Shane? What are the HC and CO numbers?
First test: CO gpm .03 HC gpm .38
Today: CO gpm .20 HC gpm .23 (better combustion than before, no?)
Limits: 30.00/2.00
CO was adjusted when X/cats/O2 installed Wednesday.
The only significant difference between the graphs of 1st & 2nd tests is the O2 reduction from 4% to .5%.
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Yup Shane looks better - slightly. No obvious signs of anything bizarre in combustion land.
I recall Louie Ott describing how, during development of his x-pipe he had problems getting the cats up to proper temperature because they were too far back from the manifold; IIRC he tried putting cats in-place of the resonators. But, they were so far back that the exhaust cooled enough to prevent them from 'lighting up.'
Do you have an idea of the motor temperature? Unless your cats are not, for some reason, getting hot enough to scrub the NOx - that's their job - lean and hot combustion would be the next thing to chase I suppose.
I recall Louie Ott describing how, during development of his x-pipe he had problems getting the cats up to proper temperature because they were too far back from the manifold; IIRC he tried putting cats in-place of the resonators. But, they were so far back that the exhaust cooled enough to prevent them from 'lighting up.'
Do you have an idea of the motor temperature? Unless your cats are not, for some reason, getting hot enough to scrub the NOx - that's their job - lean and hot combustion would be the next thing to chase I suppose.
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OK, been here done this.
As others have posted what you are describing is typical of running lean or HOT cumbustion. You SHOULD be able to pass with straight pipes though so you need to look for something other that cat's to do the scrubbing for a dirty engine.
- Fouled plugs
- Vacume leaks
- Dirty injectors
- Sure you have the right O2 sensor?
Try running an injector cleaner through the engine. You are SO close to passing. Lower octane fuel might help?? Just a guess.
Good luck and let us know,
Michael
Get the engine hot!! I ran mine in 2nd and 3rd gear(auto) for 30 or so miles and then ran the test.
As others have posted what you are describing is typical of running lean or HOT cumbustion. You SHOULD be able to pass with straight pipes though so you need to look for something other that cat's to do the scrubbing for a dirty engine.
- Fouled plugs
- Vacume leaks
- Dirty injectors
- Sure you have the right O2 sensor?
Try running an injector cleaner through the engine. You are SO close to passing. Lower octane fuel might help?? Just a guess.
Good luck and let us know,
Michael
Get the engine hot!! I ran mine in 2nd and 3rd gear(auto) for 30 or so miles and then ran the test.
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Originally Posted by worf928
Do you have an idea of the motor temperature? Unless your cats are not, for some reason, getting hot enough to scrub the NOx - that's their job - lean and hot combustion would be the next thing to chase I suppose.
It's possible the plugs that are in there are hotter than Bosch 7, haven't looked, going to replace.
Having an O2 sensor vs. no O2 sensor should've made a difference if it was mixture-related, so I think it has to be heat- or timing-related (or, both old and new cats are not right).
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Shane,
On my '88 an O2 sensor made a HUGE difference. In my case the engine was in the default "wide open throttle" map IIRC with the O2 sensor unplugged. I am not sure if you car's mapping is the same. My car ran REALLY bad w/out the sensor. I wouldn't be focusing on that though unless yours is MIA as your #'s are way closer to normal than mine were.
People swear by Bosch coppers in these cars. Again I am pulling this out of my *** but IIRC W7/W8's are the way to go.
Michael
Michael
On my '88 an O2 sensor made a HUGE difference. In my case the engine was in the default "wide open throttle" map IIRC with the O2 sensor unplugged. I am not sure if you car's mapping is the same. My car ran REALLY bad w/out the sensor. I wouldn't be focusing on that though unless yours is MIA as your #'s are way closer to normal than mine were.
People swear by Bosch coppers in these cars. Again I am pulling this out of my *** but IIRC W7/W8's are the way to go.
Michael
Michael
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Originally Posted by michaelathome
Shane,
On my '88 an O2 sensor made a HUGE difference. In my case the engine was in the default "wide open throttle" map IIRC with the O2 sensor unplugged. I am not sure if you car's mapping is the same. My car ran REALLY bad w/out the sensor. I wouldn't be focusing on that though unless yours is MIA as your #'s are way closer to normal than mine were.
People swear by Bosch coppers in these cars. Again I am pulling this out of my *** but IIRC W7/W8's are the way to go.
Michael
Michael
On my '88 an O2 sensor made a HUGE difference. In my case the engine was in the default "wide open throttle" map IIRC with the O2 sensor unplugged. I am not sure if you car's mapping is the same. My car ran REALLY bad w/out the sensor. I wouldn't be focusing on that though unless yours is MIA as your #'s are way closer to normal than mine were.
People swear by Bosch coppers in these cars. Again I am pulling this out of my *** but IIRC W7/W8's are the way to go.
Michael
Michael
I also read more praise for sticking with WR7DC's than trying anything else (although apparently I need fancier plugs for my GTS engine...Dave? lol), so I'm definitely going that route.