1994 Porsche 911 Carrera 2 (993)
It has air-cooled flat-six 3.6litre engine (CR= 11.3 : 1) and it has supercharger installed. Originally 272 hp, SC should add around 130 hp. Isn't CR=11.3 a bit high for supercharging ? What fuel will you use ?
ECU has Motronic 55pin connector and since the car has very low mileage (109 000 kms) and wires are in excellent condition, I'd like to install PnP VEMS.
Car has twin-plug cylinder heads (total of 12 plugs) and two distributors. Plan is to eliminate these and use two Bosch 2x3 coil-packs. Firing order: 1-6-2-4-3-5
I'm aware of the wasted spark configuration in twin plug system.
Here's ECU pinout for that car: 
Primary trigger is VR, 60-2 standard type.
Measure sensor resistance (likely 400..1200 Ohm)
Can you check polarity ?
Maybe measure with scope (or soundcard, but than soundcard polarity also needs to be checked) ?
Scope is best because amplitude can also be seen (for a given RPM).
If the sensor can be reached , than a simply DVM will reveal the sensor polarity
- rotate engine to a gap: eg the missing gap (push the car in gear5)
- connect DVM in 200mV DC mode, black wire to GND, red to VR signal
- when you move some ferrous metal towards sensor, DVM should read + (you only see nonzero voltage for a very short moment, while there is moving, that is flux change)
- when you move some ferrous metal away from the sensor, DVM should read -
If the polarity is reverse, the 2 wires of the sensor must be reversed (what was ground will become VR signal). If the VR sensor ground is only connected to an ECU pin (not connected to the ground of any other sensor), than there is nothing to do.
Secondary trigger is HALL sensor in the distributor. Since wasted spark, not needed.
CLT is NTC type
IAT is NTC type
Injectors will be most likely 500-600cc (have to be changed, stock ones are too small) High-Z together with transient 30V diode.
IAC valve is PWM type, 2 wires, so driven from spare IGBT or INJFET won't bring up surprises.
TPS is variable.
Under ivenstigation:
- resonance flap
- transmission input (most likely not needed since car has manual gearbox, not TipTronic)
- Vehicle speed sensor. Also probably for TipTronic, not manual.
I can add additional information about the car if needed, right now I don't now what to add more.
Can you write the pins as text ?
| Pin no | Description | VEMS pin |
| 1 | Resonance flap | |
| 2 | Variant coding | |
| 3 | MFI+ DI Relayterm 85b | |
| 4 | TRP-OPEN | |
| 5 | INJECTOR CYL3 | |
| 6 | TN Signal | |
| 7 | Primary trigger VR signal | |
| 8 | Sec. trigger HALL signal | |
| 9 | Vehicle speed sensor | |
| 10 | Oxygen sensor GND | |
| 11 | Knock sensor 1 | |
| 12 | +5 Volt supply | |
| 13 | Diagnosis "L" | |
| 14 | Sensor GND | |
| 15 | Unknown N/C | |
| 16 | INJECTOR CYL6 | |
| 17 | INJECTOR CYL1, TI Signal (?) | |
| 18 | TERM30 | |
| 19 | Electronics GND | |
| 20 | Oxygen sensor Heater | |
| 21 | Malfunction indicator lamp | |
| 22 | TRP-CLOSE | |
| 23 | INJECTOR CYL5 | |
| 24 | GND for POWER CONSUMER | |
| 25 | ACTUATION IC1 | |
| 26 | RPM Signal Ground | |
| 27 | TERM 15 | |
| 28 | Oxygen Sensor Signal | |
| 29 | Konock sensor2 | |
| 30 | Knock sensor GND | |
| 31 | Actuation IC2 | |
| 32 | Secondary air pump relay | |
| 33 | Valve tank venting | |
| 34 | INJECTOR CYL4 | |
| 35 | INJECTOR CYL2 |
||37||MFI+Relayterm 87
| 38 | Unknown (N/C?) | |
| 39 | Unknown (N/C?) | |
| 40 | Compressor switch | |
| 41 | Vacuum coasting shutoff | |
| 42 | Stepped switch | |
| 43 | Unknown (NC?) | |
| 44 | MAP Coding | |
| 45 | Engine temperature | |
| 46 | Unknown (NC?) | |
| 47 | Intake Air Temperature | |
| 48 | SS Connection B | |
| 49 | SS Connection | |
| 50 | Signal Knocking Yes/no | |
| 51 | Transmission input | |
| 52 | PWM | |
| 53 | TVS | |
| 54 | Variant Coding | |
| 55 | Diagnosis "K" |
Pins marked as "unknown NC" are the ones that were not on the pinout. I have to veryfy on the car that they're nonexistant.
Not that the car does not have cruise control and is manual not automatic (why transmission input?).
Can you unplug motronics, and do some ohm measurements as verification ?
Sensors like CLT, MAT, VRtrigger (take note of which ground signal you measured against).
We'll have to make a "Porsche" column in the spreadsheet in http://www.vems.hu/download/v3/Motronic55/
If we can do that, the PNP VEMS should be possible. The few extra wires for the WBO2 (and maybe shiftlight and launch input) should be easy through endplate.