Question on your RPM: You should see one pulse for every 2 crank revolutions, right? So if you measure 600 pulses per minute, that's really 1200 RPM, right?
Yes, I thought that this might be the case. But actually, one revolution of the crankshaft should make one pulse - piston going down and up creates one sin wave. And I’m counting only peaks at the top.
But the piston going down and up doesn't make a pulse. On a four-stroke engine, the pulse is generated when the intake valve opens, which happens once per two crank revolutions. When the piston goes down and up for the power and exhaust strokes, no pulse is generated, since the intake valve is closed. (On a two-stroke engine, you would have one pulse per crank revolution.)
Ahh, you’re right! Well, that’s an easy fix. Thank you.