MoTeC Global Forum

Hi

Is there an optimum position for a missing tooth on the crank position sensor?

I am starting with a clean sheet so can do anything I want.

For info I am going for a 36-1 trigger pattern, unless someone has a better recommendation.

As far as I know, not at any of the TDC's, due to the angular accelerations being greatest through TDC.
I would guess number of teeth depends on the sensor you have and the rpm you are going to turn, I have 40-1
on a Chev turning to 8K with a Delco magnetic sensor, seems to work fine.

Which leads to another question, where is the best position for the trigger wheel, front or rear of the crank?

Any decent modern ecu will be quite happy with the missing tooth anywhere.

If it was an extremely fast revving engine with no flywheel or something, maybe use a 36-2 to make that gap more distinct

As for front/rear of the crank, wherever is convenient !

Though you could maybe say closer to the flywheel as maybe less chance of vibration there, not that there should be any vibration anyway. But with trigger wheels inside the crankcase, they are usually at the flywheel end....likewise some install triggers on the flywheel

Of course, some install them on the front crank pulley too.

denis bassom wrote:Hi
Is there an optimum position for a missing tooth on the crank position sensor?

Actually, there are two general rules to consider for missing teeth mode (these are in the help file too BTW);
1. Keep the missing teeth away from any TDC's.
2. Keep the missing teeth outside of the normal range of timing.

If your engine is a 6 cylinder, somewhere around 60°BTDC would be ideal.

Which leads to another question, where is the best position for the trigger wheel, front or rear of the crank?

With nearly all car type engines torsional vibration amplitude is always far less at the flywheel end - so that's generally the most accurate end to sense crank position.

Thanks for all the advise everybody.....60 degrees it is then.

When I get the flywheel made I shall enquire about machining in a trigger wheel. Would solve some other issues as well (the front of the engine is a bit close to the upright/wheel, it's all a bit 'snug' in the back....most engine work on the front 3 cylinders is going to involve pulling it out...feel sorry for the guy who has got to make the exhaust manifold!).