Technical > Wiring & Sensors

Finally, first VEMS install.

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Lizard:
Ok so I have gotten a VEMS unit and am installing it onto a 1990 928 GT.

I have a couple of questions though, which going through the manual didnt seem to be really covered.

#1 is with regards to the IAC. The 928 uses a 2 wire Bosch IAC. I have used this valve with Megasquirt and it works on the PWM style IAC without any problems. But I am not sure as to which port to use. IE use inj g/h to drive, or 1 side of the 4 wire outputs on the 18 pin plug?

#2, the 928 has a vacuum actuated butterfly (flappy) used for resinence tuning. This uses an earlier version of the GM style boost control valve (same but different connector). I am needing to know what ports (preferably inj e/f in the 36 pin) I can use to drive this. I need to actuate it at a specific RPM, and hopefully turn it off after a specific RPM too.

#3 the 928 tachometer runs off of 1 of the 2 coils. This means it reads like a 4 cylinder. I am doing fully sequential COP on this car and would prefer to use a spare output port as a tach signal. Is this possible? Or do I need to tag into the signal lines with diodes (to prevent backfeed) to get my tach signal?

#4 there is also a factory fuel consumption guage in the car, it works off of the injector pulsewidth. Now the stock system has only 1 injector driver which fires all 8 injectors at the same time. So the pulsewidth will be VERY different from running 4 injector drivers (more spares) each powering 2 injectors. Could I program a spare port to output this signal as well? Or how would you recommend that I attempt to adapt this system?

TIA!

Colin

Lizard:
I also wanted to mention that I think it would be a wise idea when purchasing the harness to include 2 6M piece of 2 pin shielded (3 wire total) wire, with or without ends. As this is really needed, impossible to find locally, and not currently included.  :P

gunni:
#1. Use one of the free ign/inj output.

#2. use a relay output as it´s just a open/closed scenario it seems.

#3. You can adjust the multiplication of your tacho signal in the software to suit your tacho.

#4. This consumtion thing is not working right now but should only be a firmware upgrade away.

Lizard:
Thanks Gunni for the quick reply.

Though I have another question.

Which pin is Tach output?



I dont see it in here. And going through the manual didnt find a reference for it either  ???

Good to know that the consumption is being worked on. Which pinout will it likely be on?

Thanks again.

gunni:
Tacho would be on one of the lime green P259 channels.
A consumption output would be on one of them as well.

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