What enables COT? Rear O2 inputs?
12-03-2003, 07:03 AM
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What enables COT? Rear O2 inputs? Has anyone determined this yet? I don't have cats, but recently I was discussing this with a friend and it was mentioned that if COT was enabled by rear O2 inputs (not even sure if that makes sense, probably would be the front O2s if anything), that running O2 sims might shut down the COT. It was then mentioned that this might be an issue for people still running cats but using O2 sims to keep codes away that people somtimes get even with cats due to the farther away placement of the cats when using LTs.
So is there any merit to that? O2 sims effecting or disabling (in effect) COT?
So is there any merit to that? O2 sims effecting or disabling (in effect) COT?
12-03-2003, 09:14 AM
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AFAIK COT can only be disabled by LS1Edit. I think a few variables go into enabling COT like: Front O2 voltage, maf and prolly a few more. If you have no cats get yourr tuner to turn it off. It will be hard to zero in your A.f ratio with it on
12-03-2003, 05:36 PM
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Originally Posted by HumpinSS
AFAIK COT can only be disabled by LS1Edit. I think a few variables go into enabling COT like: Front O2 voltage, maf and prolly a few more. If you have no cats get yourr tuner to turn it off. It will be hard to zero in your A.f ratio with it on
12-03-2003, 06:07 PM
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All I have seen, indicates it's just a dumb time-at-load
trigger calculation inside the PCM. Never seen anything
about real-world inputs having anything to do with it.
Would sure like to know any different info.
trigger calculation inside the PCM. Never seen anything
about real-world inputs having anything to do with it.
Would sure like to know any different info.
12-03-2003, 10:44 PM
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Originally Posted by RPM WS6
Has anyone determined this yet? I don't have cats, but recently I was discussing this with a friend and it was mentioned that if COT was enabled by rear O2 inputs (not even sure if that makes sense, probably would be the front O2s if anything), that running O2 sims might shut down the COT. It was then mentioned that this might be an issue for people still running cats but using O2 sims to keep codes away that people somtimes get even with cats due to the farther away placement of the cats when using LTs.
So is there any merit to that? O2 sims effecting or disabling (in effect) COT?
So is there any merit to that? O2 sims effecting or disabling (in effect) COT?
The sims produce a voltage reading as if the cats are there.
If the front 02 values indicate too lean, COT will be enabled.
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12-04-2003, 02:19 AM
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Looking at the info I have regarding OBDII system theroy and operation I recieved when attending a class at the Burbank GM TrainingCenter.............
The PCM goes thru 2 stages of comparison regarding fuel trims in correlation to Pre & Post O2 readings. These 2 stages of tests walk a line between fuel monitoring and catalyst monitoring. The PCM monitors the O2's for their correct response regarding the fuel cell in which they are in, load conditions, temp, etc, and decides based on pre-programmed PCM tables as to wheather there is a fueling problem (lean or rich). The PCM looks for O2 switching and response times in milliseconds and also looks at the post O2 to confirm a possible extended lean condition. Although the rear O2 is used primarily to diagnose the inability of the cat to store oxygen, the PCM also looks for extended lean or rich post O2 readings that correspond with the Pre 02 that may indicate a fuel trim problem, thus invoking COT. According to the GM OBDII training manual, it speaks of 2 obtrusive tests that are run using a counter that goes to 49. If it fails Stage 1 & 2 of these tests, the PCM takes the nescessary steps to correct the fueling condition. This test happens in a matter of seconds.
Is that enough tech vomit for y'all?? hee-hee!
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The PCM goes thru 2 stages of comparison regarding fuel trims in correlation to Pre & Post O2 readings. These 2 stages of tests walk a line between fuel monitoring and catalyst monitoring. The PCM monitors the O2's for their correct response regarding the fuel cell in which they are in, load conditions, temp, etc, and decides based on pre-programmed PCM tables as to wheather there is a fueling problem (lean or rich). The PCM looks for O2 switching and response times in milliseconds and also looks at the post O2 to confirm a possible extended lean condition. Although the rear O2 is used primarily to diagnose the inability of the cat to store oxygen, the PCM also looks for extended lean or rich post O2 readings that correspond with the Pre 02 that may indicate a fuel trim problem, thus invoking COT. According to the GM OBDII training manual, it speaks of 2 obtrusive tests that are run using a counter that goes to 49. If it fails Stage 1 & 2 of these tests, the PCM takes the nescessary steps to correct the fueling condition. This test happens in a matter of seconds.
Is that enough tech vomit for y'all?? hee-hee!John
John Stevenson Automotive
10158 Canoga Ave.
Chatsworth, Ca. 91311
(818) 772-1737
12-04-2003, 06:47 AM
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Wow. That's some good info!
So I guess the rear O2s do have some input then. So what happens when you use an O2 sim? Their readings will obviously not be effected by changes in the mixture, so does this help or hurt the COT activation? Or does it really even matter?
So I guess the rear O2s do have some input then. So what happens when you use an O2 sim? Their readings will obviously not be effected by changes in the mixture, so does this help or hurt the COT activation? Or does it really even matter?
12-04-2003, 12:04 PM
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So, in my hybrid 67 Camaro, I have no rear 02's. I am having excessive fuel consumption. My LTRIM's are always -8 to -15. The car is definitely running rich (smell). Can a lack of rear O2's cause this?
12-04-2003, 02:06 PM
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Originally Posted by 67ls1CamaroProject
So, in my hybrid 67 Camaro, I have no rear 02's. I am having excessive fuel consumption. My LTRIM's are always -8 to -15. The car is definitely running rich (smell). Can a lack of rear O2's cause this?
emissions regs. The fronts are used to close the loop. Your -8 - -15
LTFTs do not mean the car is running rich, they mean the loop has
zeroed by adjusting by that amount.
Even zeroed, your exhaust is a stanky cocktail of combustion
byproducts. More so if there is cylinder imbalance. The cats
react them with each other (if they were there) and finish
busting them up into less smelly end products.
Rich should make mostly CO (no smell) and maybe some HC
(sweet or aromatic smell). NOx is sour / acrid and comes with
leaner mixture. If you have a rich cylinder and a lean one
you get sweet-and-sour sauce.
12-04-2003, 02:29 PM
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Originally Posted by 67ls1CamaroProject
So, in my hybrid 67 Camaro, I have no rear 02's. I am having excessive fuel consumption. My LTRIM's are always -8 to -15. The car is definitely running rich (smell). Can a lack of rear O2's cause this?
