Cannot Dial in A/F on the top end..
01-13-2008, 12:34 PM
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Cannot Dial in A/F on the top end.. Ok, we had my car on the Dyno yesterday and no matter what the car would go fat after 4000+. Even after pulling fuel at 10% or even 15% value in the 4000 up area, the car consistently would go rich in the 4000+ RPM and stay rich to the end of the pull. Fuel was pulled in Power Enrich and we tried Pulling fuel in the VE tables to no avail. Any ideas on this one?.. I will post the Dyno sheet as soon as I can. But basically it runs aprox. 12.8 until about 4,000 and drops to aprox. 11.8 and stays. As we made more pulls the A/F would go rich earlier. That is to say that when we started, it would go at 4800 and the last pull of the day it went rich at 4000. We even did two back to back pulls, and changed nothing, and it went rich sooner on the latter pull? No codes as of yet.
01-13-2008, 12:52 PM
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Unless you were running with the maf disabled VE has no affect on wot fueling.
Since you didn't mention it theres a good chance COT was still turned on which was probably skewing your commanded afr.
Over 4000 rpms the maf takes over the airflow calc completely(unless the parameter has been altered in the tune by your tuner) so moving around the pe table is simply a way of fudging it.
Since you didn't mention it theres a good chance COT was still turned on which was probably skewing your commanded afr.
Over 4000 rpms the maf takes over the airflow calc completely(unless the parameter has been altered in the tune by your tuner) so moving around the pe table is simply a way of fudging it.
01-13-2008, 12:58 PM
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Yea, we were just grabbing for straws with the VE table. Im pretty sure COT is gone. The strange thing is, that last week we had it on the Dyno and we were able to get the A/F 12.5 or so all the way through the pull. (Come to find out we had a dead cylinder and I repaired it and returned). Well now we cant dial it in all the way across. 
All I did was fix a coil connection and the exhaust has been changed from TDs to a ORY-CatBack.
All I did was fix a coil connection and the exhaust has been changed from TDs to a ORY-CatBack.
01-13-2008, 09:52 PM
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Talked to my tuner. It looks like the COT was not disabled. So that may well be our problem. We are going to try it out. (On a side note, where does the car pickup info to decide that it needs to go into COT mode??)
01-13-2008, 10:12 PM
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What I mean though, is what parameters make the computer say..."hey I bet the Cats are too hot". I mean, I dont have cats, so it can be deleted all together, but I figured maybe a certain sensor etc. makes it want to go into COT. My tuner has tuned many LS1 F-bodys and he said he has never had to disable it. The other thought is, why would we have been able to flatline the A/F one week, but not the next? Nothing really changed on the car. (Im trying to make sure I dont have something faulty before I waste anymore tuner/dyno time).
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01-13-2008, 11:18 PM
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No, you always have to disable it. Even if tuning with cats it has to be disabled and can be re-enabled afterward. It's enrichment table is skewing your WOT AFR exactly as it was designed to do. Every F-body behaves in this manner unless it is disabled.
