I have a customer with a PNP vems ecu that ever since swapping to a 7a flywheel is having some apparent trigger problems. The car ran without issues on the AAN flywheel.
The ecu IS equipped with a cam hall inverter (which is required for use with the 7a flywheel). On initial startup the car would not idle properly, with the tach displaying random high rpm values in vemstune. We were able to partially fix this by slotting the mounting hole on the vr sensor block so that the sensor reading the reference pin gets rotated closer to the face of the flywheel (the reference pin on the 7a is much smaller than the one on the AAN or other flywheels). By doing this, the car idles fine. However, around 1500rpm the same basic symptom comes back: the revs jump randomly to ~14000 rpm in the software and as you might expect, the ecu cuts fuel for the rev limit features.
Oddly, if the throttle is held in it is possible to 'rev past' this problem. Once the revs get up to about 2k+ rpm the car will rev smooth to redline no problems.
here is a zip file containing various .vemslog and .triggerlog files.
http://www.efiexpress.com/downloads/jason_trigger_logs.zip
the trigger logs seem to indicate that there are no problems with the primary trigger signal, so I suspect the problem is in some way related to the secondary trigger. The car is not local, so I'm playing somewhat blind here.
The next possible steps I've contemplated are shipping him another ecu in the hopes that an incorrect pullup resistor may have been fitted
- that can, and should be measured (DC bias voltage with ignition on)
- although I would have expected problems with the other flywheel if that was the case
- or we would expect that it does not start at all (most of the trigger problems with these VR sensors happen during cranking or cold cranking, when the amplitude is lowest)
- anyway, if it's close to margin, than - with this sensitive type, like any low toothcount VR - a tiny difference can cause it to not work
- or perhaps fitting a larger pin to the flywheel. I'd like to avoid that, since I do have customers running these flywheels without issues.
Suggestions?
This arrangement of sectrig-VR cap (2009-08 => 2010-02, appr ~2400-2900) is not as originally planned:
Although it passes tests, and it works, it is not as intended. It would more likely cause trigger problems with the higher amplitude signal (with the AAN flywheel), if ever (possibly work well without symptoms).
Do you know how it was ordered ? If 1k pulldown, 1k5 pulldown or 12k pullup or other is used for sectrig-VR ?
In any case, it would be good to know.
- What is ECU serialnr ? (order-ID or order date ?)
- Also, what is sectrig-VR sensor resistance ?
- what is measured DC voltage on sectrig-VR sensor ?
Although it's very likely a HW problem, we should inspect everything, including sw.
- firmware ?
- saved .vemscfg config ?