Corrado VR6 (HIBOOST)
3" turbo back exhaust
86# LOW-Z Siemens injectors
VEMS V3.3 w/ 30V flyback running 1.0.78RC2 16x14 tables
Electromotive 3x2 DFU's
Stock 60-2 crank trigger, no cam sync.
Conservative tune @ 8psi 304WHP/260WTQ (dynojet)
Issue with engine cutting ignition??
I just finished an install of a VEMS V3.3 on a Corrado VR6 Turbo. I successfully tuned the engine on the rolling road up to 8psi. I did not notice any erratic changes while driving. But customer says that while he is driving at a constant speed/throttle the car will 'turn off' and then after a few seconds resume with a loud backfire the engine will resume again.
Now I have had this issue once before on my friends BMW. At first I thought it was the RPM sensor (VR) and or the wiring, so the sensor was replaced with a brand new unit, and the shielded wire from the VR sensor plug back to the ECU with new wire. The problem still persisted. What I did to get rid of the issue was to load an older MSQ file and that made the problem go away. At that point all I did was import the VE, IGN, and LAMBDA tables into the older MSQ and the car ran fine after ever since.
But now I'm starting to think there is an error somewhere in my MSQ, CONFIG files? I will need to get a recent config download tomorrow from the ECU and will post up here. Strange thing is, I'm not using the same firmware version, and I didn't use the MSQ file from another tune. I started with default configs from the firmware, and made all changes via MT for the ECU options. Possible fault by doing so through MT in the config?.
- Found the cause of the problem, it dawned on me today while at work. Then applied the changes to the Corrado and all is well. The problem was the fuel cur under (kpa) setting.. it was set at 28 kpa, so during light cruise the map sensor would sit around 28 kpa or slightly lower, and then cut fuel. Set to 10 kpa now and the problem disappeared.
- Correction, the problem is still there on the Corrado, and now I have this issue as well on another VR6 turbo car. I really need help to figure this out because of then the backfire during cruise the car runs great. Seems to happen the most during cruise with little to no change of the TPS.
- Publish logs, with note of the position (eg. file ... 1452 sec) where the stumble happens.
- watch for wheel errors.
- watch for other strange things: irregular sensor reading, RPM, corr.air and corr.gamma, dwell, pulsewidth or other suspicious things
- Try to guess if it's ignition or injection cutout. (although often hard to say. Backfire makes igncutoff more likely)
- check everything in VemsTune as well. Go over all settings and tables, everything - also the features you think you do not use. Especially MAT-enrichment related, N2O and the ones GenBoard/UnderDevelopment/FirmwareChanges warns about, related changes between 1.0.73 and 1.0.78
Try these - although we cannot say at this point that any of them is likely to fix the problem
- use ignchmax=05 (not ignchmax=02) for 6 cyl, and set the first 6 entry of the h ignition outputs table
- use crank_minper=00 instead of crank_minper=9C
- try to downgrade to 1.0.73 and see if it persists.
I tried the above and none of if 'fixed' the issue. I find it hard to believe that there is something wrong with the ECU or with the trigger itself as this is happening on two different cars. Although they're both running the same firmware version!
here is a log tonight and @ 99.202 sec it shows a quick dip to 0 RPM...
Also I was having trouble trying to tune the car today, MT would freeze and the LCD would get screwed up and the WBO2 would stop working. This was happening multiple times today and I believe is directly related to this issue somehow.
I really need to get a fix for this. Any suggestions? I also believe I'm going to try to down grade the FW as suggested. Although like noted above I had this issue with a BMW running 1.0.73... The issue manifested itself out of nowhere on it's own after almost a year of driving perfectly, and the only way to correct it was to load a slightly older MSQ (although they were identical in setup only VW and spark tables were different).