MembersPage/PorscheCarrera (2007-07-31 09:12:08)

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: Porsche%20993%20Carrera2.JPG


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

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:

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 noDescriptionVEMS pin
1Resonance flap 
2Variant coding 
3MFI+ DI Relayterm 85b 
4TRP-OPEN 
5INJECTOR CYL3 
6TN Signal 
7Primary trigger VR signal 
8Sec. trigger HALL signal 
9Vehicle speed sensor 
10Oxygen sensor GND
11Knock sensor 1 
12+5 Volt supply 
13Diagnosis "L" 
14Sensor GND 
15Unknown N/C 
16INJECTOR CYL6 
17INJECTOR CYL1, TI Signal (?) 
18TERM30 
19Electronics GND 
20Oxygen sensor Heater 
21Malfunction indicator lamp 
22TRP-CLOSE 
23INJECTOR CYL5 
24GND for POWER CONSUMER 
25ACTUATION IC1 
26RPM Signal Ground 
27TERM 15 
28Oxygen Sensor Signal 
29Konock sensor2 
30Knock sensor GND 
31Actuation IC2 
32Secondary air pump relay
33Valve tank venting
34INJECTOR CYL4 
35INJECTOR CYL2 
||36||MFI + DI Relayterm 85

||37||MFI+Relayterm 87

38Unknown (N/C?) 
39Unknown (N/C?) 
40Compressor switch
41Vacuum coasting shutoff 
42Stepped switch 
43Unknown (NC?) 
44MAP Coding 
45Engine temperature 
46Unknown (NC?) 
47Intake Air Temperature 
48SS Connection B 
49SS Connection 
50Signal Knocking Yes/no 
51Transmission input 
52PWM 
53TVS 
54Variant 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.