E38 Tuning Help
Thread Starter
TECH Enthusiast
Joined: Jun 2012
Posts: 608
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E38 Tuning Help I have tried this over on the hptuner's board with no luck so I thought I would reach out to my LS1Tech brethren and request a little assistance...
The car is an 07 Cadillac CTS V with Eforce blower, custom cam (218/238 .598/.615 120 LSA +2 degrees), LSA heads, Kooks 1 7/8" headers, hi flow cats, Corsa cat back, and upgraded (large) heat exchanger and pump. I am currently trying to finalize the MAF tuning. I am currently running MAF only open loop (for calibration) and I have been at this a WHILE. However, without fail the car runs rich on initial startup and lean if I let it heat soak (short stops and restarts, stop and go traffic).
I am beginning to think that the issue is related to my separation of the IAT sensor from the MAF. The Edelbrock kit moved the IAT sensor to the TMAP sensor they provided but it heatsoaked horribly in that location. I built a thermistor based IAT sensor, did the recalibration in the tune, and installed it beyond the intercooler on the driver's side port in the blower. This seems to track with intake charge temp MUCH more closely. For some reason though I am still getting the AFR going lean (lambda 1 will go to lambda 1.08 in some cases) as the IAT diverges from ambient.
I began logging things like intake valve temp and injector tip temp but the changes in AFR do not seem to track with these variables. The AFR divergence doesn't seem to track with ECT either. I thought maybe the cylinder charge temperature bias might help but I believe this is only used in SD mode (need confirmation of this).
Anyway the tune and a couple of logs are attached. If you have any ideas PLEASE let me know. This thing has me whipped
The car is an 07 Cadillac CTS V with Eforce blower, custom cam (218/238 .598/.615 120 LSA +2 degrees), LSA heads, Kooks 1 7/8" headers, hi flow cats, Corsa cat back, and upgraded (large) heat exchanger and pump. I am currently trying to finalize the MAF tuning. I am currently running MAF only open loop (for calibration) and I have been at this a WHILE. However, without fail the car runs rich on initial startup and lean if I let it heat soak (short stops and restarts, stop and go traffic).
I am beginning to think that the issue is related to my separation of the IAT sensor from the MAF. The Edelbrock kit moved the IAT sensor to the TMAP sensor they provided but it heatsoaked horribly in that location. I built a thermistor based IAT sensor, did the recalibration in the tune, and installed it beyond the intercooler on the driver's side port in the blower. This seems to track with intake charge temp MUCH more closely. For some reason though I am still getting the AFR going lean (lambda 1 will go to lambda 1.08 in some cases) as the IAT diverges from ambient.
I began logging things like intake valve temp and injector tip temp but the changes in AFR do not seem to track with these variables. The AFR divergence doesn't seem to track with ECT either. I thought maybe the cylinder charge temperature bias might help but I believe this is only used in SD mode (need confirmation of this).
Anyway the tune and a couple of logs are attached. If you have any ideas PLEASE let me know. This thing has me whipped
TECH Apprentice
Joined: Feb 2012
Posts: 360
Likes: 3
From: Montreal
Not an expert here and don't have your stock tune to compare to, but I am surprised that the transients are disabled. Might try putting the open loop and open loop gains tables back to stock also.
Not sure what you did with that IAT sensor but those IAT temps in the 80s cant be right on an eforce unless the car was just started.
Not sure what you did with that IAT sensor but those IAT temps in the 80s cant be right on an eforce unless the car was just started.
Thread Starter
TECH Enthusiast
Joined: Jun 2012
Posts: 608
Likes: 2
The IATs track with the heat exchanger coolant temps (measured via laser thermometer). I have a MUCH LARGER heat exchanger and pump on the system. IATs typically run within 12 degrees of ambient.
The tables were disabled to eliminate some of the variables. They will be re-enabled once the AFR settles out. Specifically on the transient table, I am not logging the transient AFR because of filtering in the histogram. Filters are based on throttle position and MAP.
Thanks for the inputs though.
The tables were disabled to eliminate some of the variables. They will be re-enabled once the AFR settles out. Specifically on the transient table, I am not logging the transient AFR because of filtering in the histogram. Filters are based on throttle position and MAP.
Thanks for the inputs though.
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