VR Sensor Sync Loss Scope Traces

[derbybrit1]

I am having a sync loss problem that we are trying to troubleshoot. The configuration is a 36-2 crankwheel with a Bosch IA-C type VR sensor. The sensor is similar to p/n 026121047 (http://www.urotuning.com/shop/crank-pos ... p-964.html) except it is 2-wire unshielded.

The problem would originally occur at 8000rpm, and would appear on a tooth logger as losing teeth. Instead of logging 34 teeth/missing teeth, the tooth count might be 32 or 33. Efforts to mitigate the problem included adding resistors to the vr+ leg. Addition of 90k Ohm resistor resulted in raising the rpm ceiling to over 10,000 rpm with only occasional sync loss. It also resulted in a reduction of peak-to-peak voltage from 44v to approximately 18v.

However encouraged I might be with the improved result, I am still concerned about the irregular scope traces. Whereas I would expect to see 34 well defined AC sine wave cycles/peaks, it almost appears as an alternating high peak/low peak for every other tooth.

Additionally, I am concerned about the how the signal completely deteriorates for 1-3 cycles during a sync loss event, as shown in the first and second traces. I am trying to fix the root cause as opposed to just treating the symptom. Perhaps the attached scope traces show a pattern that is familiar? I am thinking that the problem could be the result of any one or more of the following:
1) Electromagnetic Interference being picked up by the VR sensor cable
2) Ground issues
3) Sensor failure

Any help determining the root cause will be appreciated.
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Here are the latest screen shots from today .

All scope signals were taken form the input of the VR into the box ( before the conditioner).

First one is a sync loss at 8000 rpm with no input resistor

8000_0k_SyncLoss_1.JPG

Next one is much the same ,there seems to be alot of noise on the VR signal.

8000_0k_SyncLoss_2.JPG

The last one was with 90k in series with the VR + and this was at 8500 with no sync loss , he was able to spin it to 10500 before it would loose sync now.

8500_90k_NoSyncLoss_1.JPG

[trakkies]

Are you using screened cable to the sensor?

[derbybrit1]

as stated above: 'except it is 2-wire unshielded.'

Are you saying you recognize that pattern as being related to unshielded VR cabling?

[derbybrit1]

Going to try one of the jbperf.com differential VR signal conditioner boards and some shielded cabling and see if that helps.