After we suffered a #2 rodbearing failure on a trackday (pics @ http://home.student.utwente.nl/p.h.d...orsche/engine/ ) and with a rebuild in progress now (found another shortblock as a donor/replacement) we are making the mechanical preparations for an aftermarket ECU/ignition computer. For those interested, check www.sdsefi.com for info.
We will rewire everything and tune the system a month or 2 after the car's running again so we have a baseline 'seat of the pants' feel and some numbers on fuel consumption/performance with tte rebuilt engine.
Anyhoo, the wiring diagrams show the speedsensor plugs in to the ECU, which then feeds a signal to the dashboard for the tacho. This is pretty much the only dashboard function going through there, which is obviously a bummer.
Does anyone know what kind of signal the ECU feeds the tacho and if this can be emulated with a small circuitboard, instead of leaving the entire old ECU in the car with sensors plugged in just to keep the tacho working?
Because the system we're buying is somewhat universal there's no provisions for branching off a signal to the tacho.
Any help is appreciated

BTW: for those of you with the barndoor airmeter on a 928: this system works MIRACLES for your engine: 10% less fuel consumption, ~10% more top end power, and loads of low down TORQUE, you wouldn't believe it. Not affiliated with them, just a very satisfied customer!