arubenstein
November 20th, 2014, 10:05 AM
Hi,
I am tuning an E38. The base vehicle is a 2009 Tahoe with a 5.3 and 4L60 (it is a PPV). We took the 5.3 out and put a 6.0 L96 in. The 6.0 has a supercharger on it with the smallest pulley possible (should make about 9 psi). I have had the car on the dyno for a while doing VVE which all went well. I recently shifted into doing the MAF and started to run into a problem.
My method of getting proper MAF scale is to hold the vehicle at a particular MPH on the dyno, then gently roll in to and out of the throttle, recording commanded AFR, WO-AFR and using the corrective numbers to rescale the MAF. The issue I am having is as I roll into the throttle, as I pass about 139 kpa, SEMRET starts to roll in and increases as I get further into the throttle. I see this is anoted as "Torque Reduction Retard", but I have no idea where this is coming from. The T43 has a calibration on it to never upshift or downshift from 3rd, so it certainly isn't from that. I have also (at least I think I have) turned off all formes of torque reduction. Eventually, as I pass about 148 kpa, SEMRET drops to zero, and the WO starts recording a very lean condition (goes from 9.7 to off-scale high). I attribute this to fuel being cut in some cylinders, which is evidenced by a feeling and hearing a very symmetrical cylinder loss.
Note 1: Yes, I know the AFR is way, way low - that is why I am scaling the MAF to correct this. But I don't think this is causing the issue.
Note 2: When I say "symmetrical" it is a very similar feeling to when traction control kicks in in other GM LS cars I have, where you hear one or two cylinders shutdown. This is not a random cylinder loss, and I believe that the shooting up of AFR is evidence of fuel injection shutdown on one more cylinders.
Note 3: I also see the burst knock, but I don't believe that is attributing to my issue.
Note 4: HO2S11 is disconnected (that is where the WB is plugged in).
So, my question is is this: What have I missed in the calibration that is causing SEMRET to kick in, especially considering there is no up or downshift happening? And, why is the ECM cutting fuel to certain cylinders? I believe these items to be related, an effort by the ECM to reduce torque. But why is it doing that? I have disabled TM everywhere I can find it.
The E38, T42 tunes, and a log of this happening are here:
17699
17700
17701
I am tuning an E38. The base vehicle is a 2009 Tahoe with a 5.3 and 4L60 (it is a PPV). We took the 5.3 out and put a 6.0 L96 in. The 6.0 has a supercharger on it with the smallest pulley possible (should make about 9 psi). I have had the car on the dyno for a while doing VVE which all went well. I recently shifted into doing the MAF and started to run into a problem.
My method of getting proper MAF scale is to hold the vehicle at a particular MPH on the dyno, then gently roll in to and out of the throttle, recording commanded AFR, WO-AFR and using the corrective numbers to rescale the MAF. The issue I am having is as I roll into the throttle, as I pass about 139 kpa, SEMRET starts to roll in and increases as I get further into the throttle. I see this is anoted as "Torque Reduction Retard", but I have no idea where this is coming from. The T43 has a calibration on it to never upshift or downshift from 3rd, so it certainly isn't from that. I have also (at least I think I have) turned off all formes of torque reduction. Eventually, as I pass about 148 kpa, SEMRET drops to zero, and the WO starts recording a very lean condition (goes from 9.7 to off-scale high). I attribute this to fuel being cut in some cylinders, which is evidenced by a feeling and hearing a very symmetrical cylinder loss.
Note 1: Yes, I know the AFR is way, way low - that is why I am scaling the MAF to correct this. But I don't think this is causing the issue.
Note 2: When I say "symmetrical" it is a very similar feeling to when traction control kicks in in other GM LS cars I have, where you hear one or two cylinders shutdown. This is not a random cylinder loss, and I believe that the shooting up of AFR is evidence of fuel injection shutdown on one more cylinders.
Note 3: I also see the burst knock, but I don't believe that is attributing to my issue.
Note 4: HO2S11 is disconnected (that is where the WB is plugged in).
So, my question is is this: What have I missed in the calibration that is causing SEMRET to kick in, especially considering there is no up or downshift happening? And, why is the ECM cutting fuel to certain cylinders? I believe these items to be related, an effort by the ECM to reduce torque. But why is it doing that? I have disabled TM everywhere I can find it.
The E38, T42 tunes, and a log of this happening are here:
17699
17700
17701