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Single tooth crank trigger for twin Boxer engine

Posted: Tue Jul 15, 2025 10:54 am
by bjzwart
I'm new here and after converting a Porsche 928 to megasquirt 15 years ago, I'm now in the process of converting a Citroen 2CV to EFI. this time with RusEFI, using the new Nano ECU (hopefully).
Easiest location to measure the RPM is with a VR sensor on the camshaft: There are two pins equally spaced (180 degrees) on the camshaft potentially passing by a VR sensor. The engine will run waste spark and single point injection: every rotation of the engine, a spark and 1 injection is needed. This means that for every pin on the cam, a spark and squirt is needed.

My line of thinking for TunerStudio trigger settings:
- Two stroke engine
- Trigger type: Custom toothed wheel
- Total tooth count(number): 1 (it assumes crank shaft triggers; no cam... 2 cam triggers=1 crank trigger)
- Missing/skipped tooth count(number): 0

Would this work?

in case not: I noticed a pre-defined potential 'trigger type' is 1+1. What does this mean? Would I need to use this?

Re: Single tooth crank trigger for twin Boxer engine

Posted: Thu Jul 31, 2025 4:51 pm
by mpgmike
Hopefully your triggers are advanced of TDC. I designed a small engine ignition timing controller using the stock magneto for the trigger. What I found is it was virtually impossible to predict crank angle 350 degrees after the trigger. I could easily retard timing, but advance proved unstable. I did a 7 installment article series on it for Nuts & Volts Magazine.