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Old 12-29-2015, 11:09 AM   #4
bmwman91's Avatar
Join Date: Oct 2004
Location: South Bay Area
Posts: 2,190
Awesome! Your dwell time is very close to what I have directly measured (and will make a separate thread for once I have a chance to do the same measurements on an M42 with stock coils and an M52 with its stock coils which are what we all use for the COP conversion).

Basically, the factory dwell is 3.6ms on average. It jumps around a lot, from 3.0 to 4.2ms and it seems totally random. Maybe the Motronic is old and slow or something, or maybe it has to do with the timing advance changing during the dwell period or something. Anyway, 3.6ms of dwell with the M52 coils on our cars makes for an 8 Amp primary current and the spark duration ranges from 2.2ms at idle to 0.9ms at redline.

Any chance that you can post up the settings you use for the idle control (assuming you use the stock ICV)? How about the tach and MPG gauges? From what I understand, the tach takes a 50% duty cycle square wave with 2 pulses per revolution. As far as the MPG meter, I need to get in there with a scope.
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