Autosport Labs

Actually, on kart engine, we are using a spiraled wire around the high voltage wire to detect firing and calculate the rpm (considering waste spark ignition)

Do have experienced (or expect to have) such rpm acquisition ?

I'm not a moderator but I'm sure it will work. The RPM input on the Race Capture Pro should be a digital input on a PWM circuit. It just needs to see a voltage transition above some threshold, I'm guessing a volt or two. How many coils you wrap around the high voltage circuit would determine the induced voltage level, right? The Race Capture Pro would see this edge transition and trigger the timer calculation on the PWM circuit. Regarding wasted spark, for sure the Race Capture Pro can be configured for various engine cylinder counts, so for wasted spark you would specify double the number of cylinders as the engine physically has, yes?

Keep in mind RaceCapture can't handle more than 45v and ignition coils output in the hundreds to thousands of volts. I fried my RaceCapture doing something similar. A normal multimeter won't display the millisecond spike of hundreds to thousands of volts, you'll need an oscilloscope to do that.

To detect the signal from a wire wrapped around the HT lead you will need an amplifier / conditioning circuit that can translate that into a clean square wave that can be fed into the timer / pulse of RaceCapture/Pro.

Anyone have a design resource for such a thing? Let us know and we'll lay out a schematic / board design