Tacho Problem

[TJW]

I have fitted a digital 6 system with 8600 crank trigger and 8252 HVC coil.
This is fitted to a 4 cylinder BMW engine, the unit is set to 4cyl. and rev limiter at 8000.
The engine runs OK but the Stack tacho reads double ie. when the engine runs at 4000 the tacho reads 8000 and the rev limiter cuts in, I adjust the rev limiter to 9000 and the engine will go to 4500, the tacho reads 9000 and the the limiter cuts in.
I have routed the crank trigger wire both thru. the engine bay and had it hung outside the engine bay same result.
If I set the digi unit to run 8cyl. mode and my tacho to 8cyl it works perfect but this is not the answer.
Any ideas?


Tom

[msdtech2]

When you installed the 8600 cranktrigger wheel did you remove 2 of the magnets in the wheel? It is receiving double the number of signals and that is why the tach reads double and the RPM limit is activating at 1/2 the RPM. The 2 magnets that have to be removed are the ones that are 180 degrees apart.
Thanks,
msdtech2

[TJW]

It had occured to me that by removing the two magnets it would work and I would get the correct trigger signal, but, as the digital 6 is programmable for 4yl. and no mention of removing the magnets in the instruction I did not want to invalidate any warranty.
I will remove the magnets.

[msdtech1]

That should take care of the problem.

MSD Tech1