Ok Im posting on my friends sn as im installing his Megasquirt. Ive installed my own ms but on a nissan L28ET set up.

Ive been searching for like 3 hours and i cant find out what i need. Ive read that you trigger off of the -side of the coil and to use a resistor. What i cant find is what resistor and then what port on the relay board im supposed to hook it into. Vref? The rest of it is easy to me. Its just this one thing im lost at.

Thanks for your help

 

Vref is a Voltage REFerence for the TPS, etc. It's not an input. You do want to connect the tach line to the coil negative with anywhere from a 5K to a 100K resistor - I'd start with a 10K and see how you do. The symptoms of too high a resistance will be that you get no trigger whatsoever; too low and you get very erratic RPM readings (false triggers) due to "ringing" in the signal. Ignore the following if you don't understand it: I typically use a 100K linear taper potentiometer to find the correct resistance. Very slowly Increase the resistance until it won't start, then measure the resistance of the pot. Add 20% to that value and be certain that you have a stable signal all the way to redline. You may have to adjust the value up or down a little bit. Once you determine that value place a resistor of the nearest value in place of the pot and you should be good to go...

-Mike

 

Thanks Thats what i needed. Also good idea with the Pot. It will keep me from running back and forth to radio shack.

 

Glad to help. If you have any other concerns, PM me and I can give you my cell #.

-Mike

 

I trigger my rpm signal off the -ve of the trailing coil and I get no rpm spikes at all without using a resistor. . I am however using MS2 would this account for the difference?

 

You're lucky or I've been unlucky! It seems that every FB I've installed on has been different. Maybe they changed coil specs or something similar. The 4 FB coils I have all ring like nothing I've seen yet when scoped. Thanks for the data point!

-Mike