This is confirmed to be fixed in released firmwares 1.1.95 and 1.1.96, and even in 1.1.94) but it wasn't reproduced on bench and hard to tell exactly what fixed it.
- anyone knows when exactly the problem disappeared ? 1.1.93 ? or 1.1.94 ?
- anyway, it is a good test-vector for the automatic tester
A rare problem with simple trigger causing mysterious stumbling has been noticed in <1.1.94 firmwares. This time I found a car where this was easily reproducible.
- Volvo 16 valve engine, essentially stock hardware with a larger turbo. It uses the stock distributor ignition and coil, with a simple trigger on the front damper, two teeth and a Honeywell GT1 Hall sensor.
- The trigger seems a bit broken, this might be why it shows the problem. The individual power gauge is very useful. It seems there is a 5 (!) degree discrepancy if I calculate correctly (worst to best is 400 us while cruising steady at 2200 rpm). This is going to be fixed later on of course.
The owner looked me up to do some fine-tuning and upgrade to the latest software, in this case 1.1.92, so we did and off we went to do some tuning.
Immediately we noticed how the engine started to stumble at an exact RPM, not only that, we could see the tachometer drop a little as this happened, and because the tachometer took it's signal directly from the negative on the ignition we could figure out that there was simply no spark fired at that moment. A slight lean reading from the lambda was also a clear sign. Importantly the car ran fine up to this point with 1.0.73, just minutes before.
Why it was so simple to reproduce is because of how the car is driven, it is sufficiently strong to be driven in 5th gear at 1700 rpm, around 60-80 km/h, which is common for normal city driving at cruise speed.
Download [vemslog] file of the problem.
The interesting part is only at the first few minutes of the datalog.
Here are two more datalogs and two triggerlogs, where the driving is trying to hit the problematic rpm.
Next week I will return to the car, this time we can fix the trigger wheel and set it up correctly and see if the problem persists. Any ideas on what to do/not to do?
I tried to reproduce this on the bench but so far I have been unable to do that. Some things can't be recreated easily on the bench. RPM, CLT, IAT and MAP are all in the right range but the TPS is not recreated in my tests. -Jörgen
During the tests I see that the dwell start is fairly close to the trigger, note that the trigger occur at the falling edge of the ch1 waveform in the screen capture from the logic analyzer. Ch2 is the gate of the IGBT, the rising edge indicate dwell start. -Jörgen
The session can be opened with the saleae logic software if you want to investigate the output from the logic analyzer further.