VEMS Community Forum

Technical => Triggering => Topic started by: RogueEngineer on March 17, 2025, 05:30:39 PM

Title: Poor VR triggering - Wiring pull-up resistor?
Post by: RogueEngineer on March 17, 2025, 05:30:39 PM
I'm using a Clewett VR sensor on a 60-2 wheel on a Porsche 3.2 Engine with VEMS board v3.8.

I have to have the sensor physically touching the wheel to get any useful signal. This seems to work, and when it starts it runs well all the way up to redline.

However, cold starting is very hard. I have to crank and crank, several times, before the engine shoots to life. It seems like I'm not getting any spark signal to the coils during most of the cranking, but then as soon as it gets a useful VR reading(s) it immediately fires.

This is occasional though, sometimes when cold it fires immediately, sometimes it takes 5 cranks. It seems possible that this is a trigger issue.

Seems plausible that I may need a pull-up resistor installed. My understanding is that I would install a resistor from one of the 5V output pins to the VR+ pin, correct? Would a 1/2W or 1/4W resistor work?