1990 BMW 320i DME Motronic 3.1

 

16VT’s involvement: Wired in fully functional Megasquirt ECU in a plug and play fashion; calibrated fuel, spark and idle.

 
Chassis: stock;

Forced induction: none.

Engine: 2000cc, M50B25 engine code, 24 valve,stock.

Injection: : Port injection, 151cc/min injectors, Motronic 3.1 (BMW ECU# 261 200 405) wiring harness, 60-2 trigger wheel, VR crank sensor, PWM 3-wire bosch idle valve, Bosch coolant and intake temp sensors, 6 coils driven in wastespark mode by six VB921's;

Description: The objective of this install was to use the original wiring loom. To do this, an old 88 pin Motronic ECU was cannibalised and turned into an adapter. The MS was installed inside the car, with wires running to the 'ECU' box. All the original sensors and actuators were used, including the air temp sensor integral to the air flow meter.

A v3 PCB was used, with some additions including a TIP122 for PWM idle control, an IRLZ44 for boost control, 6 VB921's for waste-spark COP capability, and a few BC337 transistors for some 'extras'. The 3-wire ISV of the car was held closed by grounding one of its pins (T88/2) via a 39ohm 50W resistor.

Pin configuration:

MS SPARE PIN (6) is freeeeeeeeeeeeeeee
MS VR- CRANK SENSOR SIGNAL (7) goes to T88/68 (green)
MS GROUNDS (8,9,10,11) go to T88/6, T88/28, T88/34, T88/55,
MS SENSOR GROUND (19) goes to T88/43
MS MAT (20) goes to T88/77
MS CLT (21) goes to T88/78
MS TPS SIGNAL (22) goes to T88/12
MS O2 SENSOR SIGNAL (23) goes to T88/70
MS VR+ CRANK SENSOR SIGNAL (24)goes to T88/67 (blue)
MS SPARE PIN (25) is freeeeeeeeeeeeeeeeeeeee
MS TPS Vref (26) goes to T88/59
MS +12V (28 ) goes to T88/54
MS SPARE PIN (29) goes to 
T88/74 (to drive cluster tachometer)
MS FIDLE (30) goes to T88/29[connector 3 of ISV])
MS INJ1 (32,33) goes to T88/33, T88/32, T88/31
MS INJ2 (34,35) goes to T88/5, T88/3. T88/4
MS coil control (36) is freeeeeeeeeeeee
MS FUEL PUMP (37) goes to T88/1 (FP relay) and
T88/27 (DME relay) needs to see ground when ignition is turned on, and to do this a relay is wired in using the ignition (T88/56) line and a ground somewhere, the objective being for the relay to ground T88/27 when it is triggered by T88/56. 
Similarly, T88/37 (O2 sensor relay) needs to see ground when ignition is turned on, and to do this a relay is wired in using the ignition (T88/56) line and a ground somewhere, the objective being for the relay to ground T88/37 when it is triggered by T88/56

The coils outputs on the external DB15 connector. Firing order 1-5-3-6-2-4, hence wastespark (1,6), (5,2) and (3,4):

Output A via 680ohm resistor to Coil 1, T88/25, DB15 pins 1 & 2 (red)
Output B via 680ohm resistor to Coil 2, T88/23, DB15 pins  9 & 10 (pink)
Output C via 680ohm resistor to Coil 3, T88/24, DB15 pins 5 & 6 (yellow)
Output C via 680ohm resistor to Coil 4, T88/50, DB15 pins  11 & 12 (blue)
Output B via 680ohm resistor to Coil 5, T88/52, DB15 pins 3 & 4 (green)
Output A via 680ohm resistor to Coil 6, T88/51, DB15 pins 7 & 8 (brown)
Good ground, T88/15, DB15 pins 13 & 14 (optional step IMO)

The 'extras':

Launch control, JS11 - SPR1, DB37 pin 3 (yellow)
Shift light CPU10, JS7 - SPR2, DB37 pin 4 (blue)
Switchable maps, SPR3, DB37 pin 5 (white)
Freeeeeeeeeeeeee SPR4, pin 6
Freeeeeeeeeeeeee IAC1A, pin 25
Boost, JS2 - IAC1B, DB37 pin 27 goes to T88/36 (evap canister)
Tacho out, JS1 - IAC2A, DB37 pin 29  goes to T88/74
Output2, JS3 - IAC2B, DB37 pin 31 (green)

Notes:

T88/17 needs +12V to feed the cluster?
T88/48 needs to be grounded for the AC compressor to work?

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