MSefi.com read only forum (Jan.15,2018)

Quick question guys, having a bit of an internal struggle here.

I have MSII V3.0, using EDIS and the relay board. I was curious about the wiring of the VR Sensor itself, with the 12' loose bundle from DIY Autotune.

Can I use the shielding of the Ignition wire as the negative(-) side of the Grey VR Sensor wire? Or do I HAVE to run a separate ground? I currently have it wired the first way, and am not getting any RPM signal in Megasquirt itself, or any spark on the ignition side.

Any help that I could get on the topic would be great. I can provide any files necessary, but because of what I have read so far, and that I am not getting ANY signal on the Megasquirt side itself I do not think it is a software issue. Whenever I use the Stim board to test my ECU I get RPM with no issue.

Best use twin screened cable to the VR sensor. I use a good quality balance microphone cable. The VR sensor has of course two terminals, so the screen is only connected at the EDIS controller. Tape it at the sensor end to make sure it can't short to anything.
Using the screen as a conductor means you no longer have a screen. If EDIS isn't working try swapping the sensor connections.

I wouldn't use microphone wire— it's unlikely going to be up to automotive use with heat and oil etc

There are plenty of places that will sell you proper stuff.

On our original wire bundle, you'd use the center core of the coax wire as + and the outer shield as the negative / return.

We've just revised the wire bundle (as in a few days ago) to use two 22 gauge wires in a foil shield for the VR sensor wire. This wire is sold on its own as well.

jcarruthers wrote:I wouldn't use microphone wire— it's unlikely going to be up to automotive use with heat and oil etc

There are plenty of places that will sell you proper stuff.

Have you any idea the rigours mic cable is subjected to on stage? Lights etc generate just as much heat as an engine block. All sorts of things get spilt on it too. It gets stood on, stretched, coiled up and uncoiled.

I very much doubt any of the sellers of twin screened for sensor use have it manufactured exclusively for this...

trakkies wrote: I very much doubt any of the sellers of twin screened for sensor use have it manufactured exclusively for this...

Well, we did have it labeled exclusively for that. We made sure to spec the maximum temperature for underhood use although I'm pretty sure they have other uses for that insulation as well.

Matt Cramer wrote:

trakkies wrote: I very much doubt any of the sellers of twin screened for sensor use have it manufactured exclusively for this...

Well, we did have it labeled exclusively for that. We made sure to spec the maximum temperature for underhood use although I'm pretty sure they have other uses for that insulation as well.

Decent mic cable would use the same sort of insulation as plug leads. Needs to be strong and flexible. Of course the fact I have drums of the stuff in stock might influence my judgement.

Matt Cramer wrote:On our original wire bundle, you'd use the center core of the coax wire as + and the outer shield as the negative / return.

We've just revised the wire bundle (as in a few days ago) to use two 22 gauge wires in a foil shield for the VR sensor wire. This wire is sold on its own as well.

So using the center of teh Coax as (+) and the shielding as the (-) is A-OK then? Good news! I will ensure that the wiring is okay (i.e. no shielding touching center conductor/etc), and continue trouble shooting! Takes one thing out of the equasion of getting no RPM Signal or Spark

Thanks for your help!

Yes, we've wired up quite a few cars that way.