Ok I have been working on this on and off for quite some time. The linked photo is my latest iteration of what I think the wiring should be. I have bench tested most of it but would appreciate any comments as with anything you get to the point where you can not see the forest through the trees. I just want to make sure I have not done anything really dumb.
good lord! i was expecting something like mine drawn in crayon! this is impressive!
Trying to make it plug and play with the exception that I have installed an EDIS ignition replacing the stock Porsche cap rotor and coil.
Ohya I am going to use the TPS form a 951 as it is varable. The NA ones are just on off switches and I will be using a MAP to get rid of the AFM and a GM IAT sensor in the tube that replaces the AFM. I will be using the same circuts / wires for the IAT sensor that were used by the IAT in the stock AFM
The tach is my last thing to figure out. There are two wires to the DME for the tach. I have traced both on the porsche wiring diagram but it is unclear what is what and if the stock Porsche VDO unit is compatible with the signal generated by the MS.
On my 924, the factory VDO tach is driven directly from the tach pin on the EDIS module.
It isn't directly compatible with the tach solutions internal to the MS unit. You have build an external solution to control many OEM tachometers with MS.
Then the simple solution seems to be pull a wire from the tach pin on the EDIS unit and call it good.
At least until you drive the coil pack directly from MS (to improve the resolution of the ignition and find a few more horses hiding in the curve)
Ok I sorted at least part of the tachometer wiring today. Looking at the wiring harness that goes to the DME plug there is no wire in the DME pin 21. So this only leaves the DME pin 11. Now all I have to do is see if the signal from the MS works with the VDO tach that is in these cars.
In case anyone cares there are no wires in the harnes that conect to the pins 10, 12, 21, 29-34 on the dme
