1986 BMW 325i twin turbo


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

Chassis: stock;

Forced induction: Twin CT20 turbos from a diesel, EVO6 FMIC, dBilas 48mm throttle bodies.

Engine: 2500cc, M20B25 engine code, 12 valve, EVO6 85mm pistons.

Injection: : Port injection, 560cc/min lowZ EVO6 injectors, Motronic wiring harness, 60-2 trigger wheel, VR crank sensor, Bosch coolant and GM intake temp sensors, 3 Audi coils driven by VB921's;

Description: The objective of this install was to use the original wiring loom. To do this, an old 55 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, with the exception of a GM air temp sensor to replace the one in the air flow meter. 3 wires were run externally from the Megasquirt to the 3 Audi coils.

A v3 PCB was used, with some additions including a TIP122 for PWM idle control, 3 VB921's for waste-spark capability, and a few PN2222A transistors for some 'extras'. The 3-wire ISV of the car was held closed by grounding one of its pins via a 39ohm 50W resistor. An M50 TPS was connected but the original Motronic TPS wires had to be swapped over for compatibility.

Pin configuration:

MS SPARE PIN (6) is connected to T55/7
MS VR- CRANK SENSOR SIGNAL (7) goes to T55/48
MS GROUNDS (8,9,10,11,12,13) go to T55/2,T55/14,T55/24
MS SENSOR GROUND (19) goes to T55/19, T55/26, T55/10
MS MAT (20) goes to T55/44
MS CLT (21) goes to T55/45
MS TPS SIGNAL (22) goes to T55/53 (WOT switch, brown/black)
MS O2 SENSOR SIGNAL (23, brown) goes to T55/28
MS VR+ CRANK SENSOR SIGNAL (24)goes to T55/47
MS SPARE PIN (25) goes to drive coil B externally wired
MS TPS Vref (26) goes to T55/52 (idle switch, brown/blue)
MS +12V (28 ) goes to T55/27
MS SPARE PIN (29) goes to T55/6 (to drive cluster tachometer)
MS FIDLE (30) goes to T55/4
MS INJ1 (32,33) goes to T55/16
MS INJ2 (34,35) goes to T55/17
MS coil A control (36) can go to T55/1  but it was wired up externally in this install (yellow wire)
MS FUEL PUMP (37) goes to T55/3 (FP relay) and
T55/36 (DME relay) needs to see ground when ignition is turned on, and to do this a relay is wired in using the ignition (T55/27) line and a ground somewhere, the objective being for the relay to ground T55/36 when it is triggered by T55/27.

The 'extras':

Launch control, JS11 - SPR1, pin 3 (yellow)
Nitrous, JS1 - SPR2 (pink)
Switchable maps, SPR3, pin 5 (blue)
SPR4, pin 6 is freeeeeeeeeeeee
Coil B IAC1A, pin 25 (blue)
Coil C IAC1B, pin 27 (green)
Tacho out, JS0 - IAC2A, pin 29
Output2, JS3 - IAC2B, pin 31 (red)