im building an adapter harness and was wondering if the pins not used on the old ecu side can be cut or not.

and the pins are numbered looking at the front or the back of it, both for the ms side and car side??

 

Be careful. I don't know what vehicle you're adapting *to*, but the MS gives constant power to the injectors and then grounds them at the ECU, while the GSL-SE computer gives constant ground to the injectors and gives power through the ECU. I don't know what the later ones do but I wouldn't be surprised if the Series 4 stuff if not Series 5 worked the same way. An adapter harness would be trickier to do since you have to allocate extra wiring for those issues.

 

its for a s4 n/a

 

S4's have constant 12v to the injectors, switched ground, so that specific problem shouldnt be a problem. The pin layout is in the FSM under fuel & emissions control. As for making the actual harness, theres no harm in leaving the wires on the stock wiring harness just in case you ever want to go back to the stock ECU.

There are some inputs and outputs that have a fixed pin, these can be found in a picture at the end of the megasquirt document showing how to build the V3 (or V2.2) board. Other outputs, such as the ones for the FC's ignition and the second VR sensor can be passed through on the IAC pins (used for non-PWM idle valve control, our idle valves are PWM so we dont use these pins for other things) or SPR pins (spare, just meant to pass signals through). Also, the fuel pump relay does not have a pin on the harnesses to the ECU, so to get it to turn on, you'll either need to keep the MAF on there, or find the plain brown wire in the emissions harness and run it to the appropriate pin on the megasquirt.

My Pin-outs from DB37 connector to stock ECU plugs:
1
2---G- CAS blue ----------------------------------------1P
3---G+ CAS green ---------------------------------------1N
4---IGT-L, Leading Timing, neg. LED 14------------------1V
5---IGS-T, Trailing Select,neg. LED 15------------------1U
6---IGT-T, Trailing Timing,neg. LED 16------------------1X
7---Ne- CAS white---------------------------------------1Q
8---Ground-------------------------------------connect to below
9---Ground----------------------------------------------2R (which is ground per FSM)
10--Ground----------------------------------------------3A (which is ground per FSM)
11--Ground----------------------------------------------3G (which is ground per FSM)
12
13
14
15
16
17
18
19--Sensor Ground---------------------------------------2C
20--Intake air Temp-------------------------------------2L
21--Coolant Temp Sensor---------------------------------2I
22--Throttle Pos. Sensor Signal-------------------------2G
23--O2 sensor-------------------------------------------2D
24--Ne+ CAS red-----------------------------------------1T
25
26--Throttle Pos. Sens. Ref. voltage--------------------2A
27
28--Main Relay (Power in)-------------------------------3I
29--Clutch Switch---------------------------------------1L
30--BAC valve-------------------------------------------2Q
31--Shift Indicator Light-------------------------------1K
32\___Primary injectors___________________/3C
33/.................................................. ....................\3E
34\___Secondary injectors________________/3F
35/.................................................. ...................\3H
36
37--Fuel Pump Relay---------brown wire, no number

Also here are the wires for lead and trail coils


neg. LED 14----------------1V
neg. LED 15----------------1U
neg. LED 16----------------1X

Vr2 In - Crank Angle Sensor (+G) --1N - green
Vr2 Ground - C.A.S(-G) ------------1P - blue
Pin 7 - Crank Angle Sensor(-Ne) --1Q - white
Pin 24 - Crank Angle Sensor(+Ne) --1T - red

REMEMBER! do not just use this, verify that your CAS, ignition, and things like the clutch switch and shift light are in the right place!