E38 PCM Tuning Help
08-03-2014, 09:48 AM
#1
E38 PCM 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
08-03-2014, 09:17 PM
#2
TECH Fanatic
You're running the LS3/7 MAF, correct? Have you swapped back to the LS2 MAF and see if things get any better? What fuel pressure are you running? If you enable closed loop what do your LT's do? From what I understand, the DW301 can overwhelm the OE regulator when cold and you get extra fuel pressure when cold.
I noticed this as well and tuned mine hot and leaned out for the cold start using the open loop fuel adder tables. It's more of a bandaid until I get some free time.
Hope all is well!
I noticed this as well and tuned mine hot and leaned out for the cold start using the open loop fuel adder tables. It's more of a bandaid until I get some free time.
Hope all is well!
08-04-2014, 11:39 AM
#3
Damian,
Thanks for the response. You are correct I am running the LS7 MAF. I haven't tried going back because I don't think I can without MAJOR pain.
On the potential fuel pressure issue, I installed a sensor at the rails and the pressure maxs at 60 psi with mins around 54-55. Pretty stable. I did a lot of logging to eliminate fuel pressure as an issue. If anything it drops more than I would like on WOT. I thought the BAP would do more to stabilize the pressure. It helps but doesn't eliminate the drop.
Hope all is well with you. Things on this end aren't too bad but m son's WS6 was totaled Friday while it was parked in a parking lot. Sooooooo looking for other good ones...
Thanks for the response. You are correct I am running the LS7 MAF. I haven't tried going back because I don't think I can without MAJOR pain.
On the potential fuel pressure issue, I installed a sensor at the rails and the pressure maxs at 60 psi with mins around 54-55. Pretty stable. I did a lot of logging to eliminate fuel pressure as an issue. If anything it drops more than I would like on WOT. I thought the BAP would do more to stabilize the pressure. It helps but doesn't eliminate the drop.
Hope all is well with you. Things on this end aren't too bad but m son's WS6 was totaled Friday while it was parked in a parking lot. Sooooooo looking for other good ones...
