wiring questions for M.S. need help

[kennedy]

ok so Im a noobie on this site but not really to e-30s. Ive built three Spec e-30 in the last 4 years. But now on to my question does anybody know what wires that come from the fuse box and merge with the engine harness are.I would like to know so i can start building a mega squirt harness for my high compression 2.7is. a pin by pin reference would help a lot.

thanks in advance
shane

[jlevie]

Below is what I've gleaned from various sources and ohming out and early and late harness. Since I was using a late harness in an early car and not all functions were needed (it is a race car), I was only concerned with incompatible differences, like pin 20.

Engine harness connections to C101

Pin Early (through 8/87) Late (from 9/87)
1 Alt Sense Alt Sense
2 Oil Level Static Oil Level Static
3 NC NC
4 Coolant Temp Coolant Temp
5 Oil Pressure Oil Pressure
6 Fused Ignition Fused Ignition (to fuel pump relay 30
7 Ignition Ignition (to coil positive)
8 NC DME/Idle Ctrl
9 NC Tach
10 Oil Level Dynamic Oil Level Dynamic
11 SI Reset SI Reset
12 Diag Plug? Diag Plug?
13 Fuel Pump Relay Fuel Pump Relay
14 NC Speed Signal
15 NC Unloader Relay
16 Diag Plug Diag Plug
17 NC NC
18 NC Hot when starting
19 NC NC
20 NC To main relay

Note that pin 20 in an early car is grounded on the body side. Using a late
harness in a early car will smoke the wires to the main relay unless you clip
the wire (engine side) going to pin 20.

[nando]

http://www.325ix.com/megasquirt/MS_to_Motronic/ms_to_motronic.html

easiest way by far is to use the stock engine harness. There's nothing really in the fuse box that you need to worry about. You need to gut an old ECU to use for the base/connector of course.

you may also consider one of the plug and play solutions - I highly reccomend you look at the www.diyautotune.com site, and search for their DIYPNP product. Basically all you do is build the adpater and plug it in to your car (plus some sensor changes of course). They even have a base map for a completely stock M20B25.

[kennedy]

thanks jim just for reference what does Nc mean. Nando i have searched diy i really need to call them. this is still a street car with most street car functions. But i want to get rid of the afm for a map sensor and the distributor for wasted spark

[nando]

I think maybe no connection

in any case if you go the PNP route you don't need to do anything with the C101

[jlevie]

Correct nc == no connection

[Rolla1990]

http://www.diyautotune.com/catalog/bmw-motronic-pin-adapter-pcb-p-194.html

^^^^ This is what you need. I built this for my setup and it works great. Forget about building your own wiring harness, this plugs in to the MS on one end the your stock harness on the other end. This includes all the outputs you need for everything to run your engine, and your tach will still work.

The only wiring mod you will have to do is for the throttle position sensor, so you can use a e36 TPS instead.

Ninja Edit: Check out the last few pictures here to see what I did.

[kennedy]

http://www.diyautotune.com/catalog/b...pcb-p-194.html

^^^^ This is what you need. I built this for my setup and it works great. Forget about building your own wiring harness, this plugs in to the MS on one end the your stock harness on the other end. This includes all the outputs you need for everything to run your engine, and your tach will still work.

The only wiring mod you will have to do is for the throttle position sensor, so you can use a e36 TPS instead.

Ninja Edit: Check out the last few pictures here to see what I did.

so you actually use that board as a dummy to run the ms through? or can you take and use that board to build the whole ms unit b/c that would be great

[kennedy]

upon further inspection i think i got it the large view helped lol

[nando]

it plugs into the MS and the stock harness, and has some extra space for things like coil drivers, boost control, idle control, main relay circuit, etc.