Harness length?

[mk e]

This has probably been covered somewhere and I’m just not very good with picking the right words to search, but a project I’m working on looks like it really wants the ECU (M800) to be 5-6M or wire away from the engine. The igniters will be back by engine but the ignition expander will be right next to the ECU (this is a V12 with 6 coils), the injectors are14 ohm. I haven’t picked the crank/cam sensors yet.

Other than the obvious wire gage cals/concerns is there anything else?

A reason to pick VR vs Hall sensors due to the extra length?

Maybe run all the sensors in a separate harness?


Thanks, Mark

[Martin]

Ive done many installations with a total length of about 4 - 5m to the ECU.

Use heavier gauge for DBW and injectors. If the igniter is in the back i wouldnt worry about using heavier gauge for them singe the igniter drives the coils which is nearby. When the ECU`s earth or power supply or the DBW wires themselves are not up to scratch you will most likely see in in the DBW first. When you do the DBW calibration and you are in the test screen with the open close cycle running then you will see the ECU battles to get it to position. It may also be jittery even trying to hold a steady position.

Ive dealt mostly with Hall (GM LS1,2,3) and have no issues. I did however screen the wires in the main harness. In the OEM harness there are no screen wires. Where you have the long stretch of signal wires running parallel to the other wires then maybe screen them. Remember not to loop the screen, only earth the screen on one side of the screen wire.

I normally also EARTH the screen and dont take it to 0v. I know its not like that on the motec drawing....just my preference.

long lengths of wire will influence the resistance of temp sensors etc....but if you look at how high the resistance is of the sensor itself then the extra 15ohms per 1000ft will really not make a difference. 22g m22759 wire is about 15ohm per 1000ft...a Bosch temp sensor will vary about 60-ohms from 90 to 100degC, as you can see, it wont do much.

Hope this helps

[mk e]

It does help to know someone's actually tried it before with no real issues, thanks.

I don't have DBW to deal with on this so that's a plus.

Mark