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Flywheel triggers <---Plural


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I have BMW M10 engine. This is a 2.0l 4-cylinder engine, boosted. I am in the process of building the turb and all the stuff needed. I am only missing the fuel pressure regulator which is due to be delivered today, so I can try to start it for the first time.


Well anyway, I have the M30 flywheel and the getrag 265 transmission. I was planning to use the two motronic sensors that are situated on the transmission near the flywheel. The first sensor is using the starter ring gear and the other one is using a mark at TDC. The starter ring gear have 116 teeth and this will of course be 3.1 degree between the teeth. and a whopping 14.5 KHz @7500 rpm.

Will any of the Link ECUs be capable of using these two trigger sensors?

A 36-1 wheel at the front is not an option because the amount of fabrication skills needed is too high. The sensor is normally placed on the hot side of the engine on the M10s but there is no room for it there.






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4 cyl engines due to the abrupt 180 deg compression events always tend to "stop" at a similar crank angle.  So your starter always engages in these same two areas and over time you get two small patches of worn teeth on the ring gear 180deg apart.  When the wear is bad enough it effects the waveform and amplitude of the signal so much that you you will struggle to trigger off them reliably and you will get trigger errors - usually at high RPM.  

I dont have any direct experience with the M10, but Porsche 944's with the similar motronic system used to be terrible and even with the oem ecu you would have to replace the flywheel every ten years or so. 

35 minutes ago, 02dag said:

Can this be seen in logs or be noticed somehow?

Yes you can see it in the triggerscope.

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Thanks for answer. If this problem becomes too bad a 36-1 wheel or similar have to be added even if its an effort.

Could this problem be filtered away programmatically if it becomes too bad? I mean the starters toothed wheel will always put force onto the flywheel teeth on one side and the wear will be bigger there. So as an example using rising or falling edge depending on which side the wear is could help rectify the problem?

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A reluctor wave form rises as metal moves towards the sensor and falls as metal moves away from the sensor.  The trigger point is where the wave form crosses zero volts - which should be right in the center of the tooth - if the tooth is symmetrical.

Worn teeth however not only distorts the shape of wave form but due to "less metal mass" being moved past the sensor the voltage that is generated is much smaller.  This is usually the biggest problem.  You will have 4 areas around the flywheel where the voltage coming off the sensor is much lower than all the other teeth.

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