I installed a Motronic pnp on an Audi S4 where the main modifications to the engine were :
- Siemens 630 cc/min injectors @ 3.8 bar
- VAG 115R coils
- Larger turbo, tubular exhaust manifold
With firmware 1.1.81 it runs very well 99% of the time and gets good fuel economy. But there are a few problems.
Trigger errors
Sometimes the ECU flags "Too many Pr trig.". You can see small dips and peaks in the rpm even though there are no errors reported, so something is not right here and obviously not reported. The trigger error event can happen has been seen to happen at idle a lot but never occurs 99.9% of the time.
The secondary trigger edge is set to "rising" as that is the same setting as in the factory setting when delivered from VEMS HQ.
- Should I try "falling" edge instead?
- That might offset the ignition timing if it skips a primary tooth, so a strobe light will verify the timing.
Some things to be done.
- The coil grounding needs to be double-checked, I will make sure the power ground on pin 4 of the coils is connected to the head, and that pin 2 is not and connects to the harness ground instead.
- I will also a double-check if the coils make good contact with the ignition plugs.
Here is a log : http://www.vems.hu/files/MembersPage/MattiasSandgren/vemscfg/audi-s4-v3.3_n002993-2010.10.05-18.34.34.vemslog.zip
- 2:56 into the log it starts to get trigger errors at idle, lasts for a good minute.
- WOT pull at 10:16 @ 4300 rpm causes trigger error
Idle
The idle air valve doesn't work very well, even when used only with refDC table without any PID regulation. If you force the position you can sense that it overshoots when it moves, like it has great inertia. The exact same settings work flawlessly on other cars, so I assume the valve needs to be replaced.
Q: Is there an internal diode in the PnP ECU to cut the flyback voltage?
Like a Schottky or similar diode, the injector flyback is not enough I assume?