DFCO may be the devil...
03-29-2005, 09:11 PM
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DFCO may be the devil... Apparently DFCO has other uses. I got it working properly by analyzing my logs and plugging the right values in (+15kpa on enter and exit MAP). Now my fuel trims are way closer to what they should be because they are not going mysteriously rich on decel. Does this make sense to anyone else that this would happen? My reasoning is that under normal throttle (low vacuum) at x airflow your fuel requirements are different than the same airflow during decel (high vacuum). Just looking at the VE table this makes sense to me, and having DFCO working seems to "mask" the problem. The only place it does not seem to help is -10mph where DFCO is not active...but that is also where proportional idle (if it were enabled) would affect the trims...so that is the next thing I will tinker with since everything else is actually working now. The reason I bothered with getting DFCO working is because the PCM seems to want to dump extra fuel in the engine during decel and this was making my trim spread really high. This seems to have decreased the spread by a considerable amount.
03-30-2005, 12:57 PM
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Your trims go positive in DFCO mode? Mine go to 0. Sometimes the trims spike coming out of DFCO, but not most of the time. Are you sure you got all of your DFCO settings right?
03-30-2005, 04:44 PM
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Originally Posted by HumpinSS
I am not sure about the trims since i am using a WB. But i will assume they 0 out when the FTC=DFCO
19:1 is the lean limit on the WB so DFCO is working
19:1 is the lean limit on the WB so DFCO is working
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03-30-2005, 05:17 PM
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Originally Posted by JimMueller
With DFCO enabled, my AFR would spike really lean letting off the gas, anywhere from 16-19AFR in MAP15.
03-30-2005, 05:52 PM
#9
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Another - I have the same issue with the car under decel in gear A/F will go to 11:1 and sit there, then get back on the gas it spikes up to 16:1 or so then falls back into place.
is this what you would see as well?
if yes what were all the things to did to eliminate the problem?
is this what you would see as well?
if yes what were all the things to did to eliminate the problem?
03-30-2005, 05:57 PM
#10
Originally Posted by Another_User
Your trims go positive in DFCO mode? Mine go to 0. Sometimes the trims spike coming out of DFCO, but not most of the time. Are you sure you got all of your DFCO settings right?
03-30-2005, 08:06 PM
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Originally Posted by Blackbird
Another - I have the same issue with the car under decel in gear A/F will go to 11:1 and sit there, then get back on the gas it spikes up to 16:1 or so then falls back into place.
is this what you would see as well?
if yes what were all the things to did to eliminate the problem?
is this what you would see as well?
if yes what were all the things to did to eliminate the problem?
Originally Posted by Flame Throwing SS
Yup, depending on the cell I am in ... as much as 6 or 7 on the LTFTs. My DFCO settings are factory stock, I have not touched them yet.
03-30-2005, 10:10 PM
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Originally Posted by HumpinSS
I see the opposite. DFCO cause lean 19:1 spike on my ve table
Chalk me up as another one that saw lean spikes with DFCO enabled.
03-31-2005, 08:10 AM
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Originally Posted by SmokingWS6
DFCO should read very lean, if any reading at all. On my scanner everything goes to 0 or freezes and injector pulsewidth goes to 0. If i'm decelerating with my foot on the brake, no dfco, i'm slightly rich.
03-31-2005, 09:53 AM
#17
When I was refering to DFCO lean I mean o2 readings, my LTFT freezes around 0. At low speed with your foot on brake DFCO can't be actve or the motor would die because the TC clutch unlocks when foot is on the brakes.
My DFCO is factory stock but I'm sure it works differently in M6's.
My DFCO is factory stock but I'm sure it works differently in M6's.
03-31-2005, 10:09 AM
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Originally Posted by pknowles
Code:
When in DFCO my LTFT goes way lean as well.
I should rephrase…My LTFTs go way positive and my AFR pegs at 19.x on the scan tool and the WB shows 20.7.
John
03-31-2005, 01:11 PM
#19
The only time I ever hit DFCO was in the Smoky Moutains, on very steep hills. If I was in 2nd, for example, and the car was still accelerating and the rpms exceeded a certain point, the exhaust note would suddenly change and you can tell more of a load on the engine. It shouldn't just happen when you let off the gas under normal conditions!
03-31-2005, 01:14 PM
#20
Originally Posted by MikeMs01TA
The only time I ever hit DFCO was in the Smoky Moutains, on very steep hills. If I was in 2nd, for example, and the car was still accelerating and the rpms exceeded a certain point, the exhaust note would suddenly change and you can tell more of a load on the engine. It shouldn't just happen when you let off the gas under normal conditions!