MS3Pro and Speedhut gauges

[SH4DY]

Alright, so in my infinite wisdom (read: very flawed) I had planned on tying into the Speedhut sensor harnesses for ECT and oil pressure inputs for the MS3pro. But, now that I'm looking at the wiring diagrams, the MS3 has a dedicated sensor return/ground whereas the Speedhut gauges just use chassis ground ( at least on the gauge side).  Now I'm kind of stuck as I'm concerned sharing potentially dissimilar ground planes may screw up more important readings like the cam/crank signals.

So, I've got three options as I see it:

Try tying both the signal and return/ground together (ms3 sensor input and speedhut sensor harness) in the gauge harness before the gauge.

Run the sensor right to the MS3 and try to use one of the analog outputs to replicate the sensor output to the Speedhut harness.

Suck it up and run a dedicated ECT and oil pressure sensor for the MS3pro.

 

Anyone else run into this?

[softopz]

I wouldnt tie into sensors grounds for the reasons you described above.

CLT sensors are like 20 bucks (pm me I carry metric and npt type with connectors) if you sucked it up for an ms3pro and speedhut. You dont have to run the oil pressure sensor for ms but with so much spares inputs , it is a nice additional add on you can set parameter like limp mode if oil pressure goes down etc.

[Chickenman]

Run the MS3 ECU main grounds to the engine. ( As per MS Extra Hardware manual ) .  Intake manifold or cylinder head preferred. " Star Ground " the Speed Hut gauges to the same point on the engine as MS ECU ground. Voila. No voltage potential difference.  Gauges can be grounded to engine, battery or Chassis. When running as a stand alone gauge  it doesn't matter where you ground the gauge.  But when tied into an ECU they need to be on the same ground plane. 

 

 Chassis grounds on 40+ year old Vintage cars are the worst place to ground ECU's and other engine devices. .