Porsche 911 3.3 Turbo
This car came to a friend of mine for mapping as he knows the specifics of these cars. But it was soon clear that the car needed more then mapping, it showed signs of trigger problems.
Specification
The spec is VEMS v3.2, 1.0.36 firmware, MSD DIS-4, proper waste spark coils, copy of original 911 turbo triggerwheel from a late model car. BMW VR sensor. The problem is that the triggerwheel is badly positioned, the missing teeth is around #1 TDC. More to come.
Problem
At high loads it banged and shot very violently, when going through the register at lower loads it just showed some hesitation. This is pretty common.
Tests and results
Full indexing (Strobe light)
When strobing the car on each coil it seem to fire at least one of the coils 120 degrees off now and then at idle. It's impossible to see how often but it happens.
Wheel error counter
The wheel error counts up to 1-2 during initial cranking and can count up when the cars idle is let down low enough for it to almost stall (3-500rpm). When the bang and cutout problem occur the wheel error counter _does not_ count up. Is the wheel error counter a reliable way to make sure that there are no false triggs or can some types of errors sneak through?
Scoping triggersignal
Redundant as the wheel error counter said everything was ok but as this is the only chance I have to scope the car I did it. The trigger signal was marginal in the missing tooth area, this is what made me doubt the wheel error diagnostics. It looks like it could almost arm the trigger for doing a false trigg in the missing tooth area.
check my_make, if it has MY_CONF += -D ALLOW_SLOPPY_TOOTHWHEEL (uncommented), than it tolerates 1 less toothcount (eg. 34 instead of 35). This is because it assumes that the tooth after the missing tooth was not sensed and everything was delayed 1 tooth (10 degree for a 36-1). There is no reason to completely cut power in this case (someone in Estonia claimed his engine needs ALLOW_SLOPPY_TOOTHWHEEL to run).
Idle:
Around 2k:
Around 3k:
5-6k:
This wheel is useless, at least with VR sensor. Do you have a drawing, or picture of the missing tooth area to educate the future generation ?
I know the flywheel trigger is badly designed and that the triggersignals is dangerously close to a false trigg but the wheelerror counter does NOT count up when the missfire problem occur! Does this mean that the wheelerror counter can't be trusted?
The bad triggerwheel design:
