PWM AIC Valve with V2.2

[1983sc]

Is it possible to run a Porsche 3-wire PWM valve for idle control with a MS-2 v2.2 board? If yes, what does the circuit look like? Thanks

[Matt Cramer]

Yes. You'd wire the side that opens the valve to a PWM circuit, and ground the other side through a power resistor.

[Heribert]

Not so important. Anyway, $0,02

The grounding resistor , 35-40 ohms does not need a 50 watt rating.
10 W is more than sufficient. 5 Watt will work becomes quite hot.

Using one of the aluminium canned resistors which screw on to a support makes a real neat
install.

Heribert

[1983sc]

Matt, Thanks for the feedback and diagram. Can I use the Q5 circuit as a place to mount the transistor (T120) and feed the fast idle output on my relay board? If so, should I use the bottom of the MS case as the heat sink and go into the bottom of the Q5 circuit? Or should I mount the transistor on the end panel above the 37 pin plug and run jumper wires to Q5. If Q5 is not a good place to connect the transistor, where else do I put the it? I currently have a jumper wire for the MS 2 ignition module running to Q5. But I understand that I can move that to X11 through X14. Thanks again for your great support.

[Matt Cramer]

I'd recommend bolting the transistor to the case, using a length of jumper wire.

[1983sc]

I added the T120 to the Q5 fast idle socket and pulled power of the board with the IN4001 that was already mounted to the board as suggested. Now I show no voltage on the MegaTune display. I have ~12 volts into the board at pin 28 of the 37 pin connector. I also get ~12 volts on the board at JP1 #6 and at other IN4001's around the board. On the stimulator I get a fuel pump signal and flashing injector leds until I go beyond cranking rpm. Than I lose the injectors (pulse width goes to zero). I've re-flashed the code, upgrading to 2.888. It did flash and validate, although I had a low voltage warning. Where does the voltage signal get measured for MegaTune? Prior to making it I had the MS 2 in the car and it was running. I was just looking for a better way to control cold idle. Any suggestions of what might have happened with this change and what to test or change? Thanks

[Matt Cramer]

It sounds like your firmware is corrupted. Try reloading the code and see if the problem goes away. Don't reuse the MSQ that you have as if your firmware is corrupted, using this MSQ will bring the problem back.