www.MSruns.com read only forum (Jan.15,2018)

I'm debating whether or not I should buy an E39 M5. However, I would really like full control over fuel and ignition (I have an AEM EMS on my 3000GT VR4, and boy, is it nice).

Anyway, with all the fancy gizmos of the E39, there's no way I could make a megasquirt work alone. However, what do you guys think about keeping the stock ecu and adding the megasquirt. The hitch is that I would send all of the inputs to the stock ECU that it normally would see. However, I would cut the outputs to the ignition / fuel system. This way the ecu would think that it were controlling those systems, but instead I would be using a megasquirt and all necessary components to control fuel / ignition.

The stock ECU would still control VANOS (throttle and load based, no?) and all of the other things that it would do. But I would simply have control over spark and fuel. The only big problem that I can for see is the fly-by-wire throttle. I need to keep it so that I can send the signal to the stock ECU, but I need to figure out some way of using the signal for the squirt.

Thoughts?

I don't know about the E39 but lot's are people are running MS in conjunction with the factory ECU's including myself on a Ford EF falcon. You may just have to add some extra temp sensors aswell.

Thanks for the help, and sorry for posting in the wrong section.

That would work fine I guess, classic LPG systems are added the same way. A word of warning - do not simply "cut off" the coils/injectors. I don't know if that's been fixed in E39, but earlier BMW COP ECU's would get damaged if left to work with the coils disconnected. Also ECU would throw error codes if it feels something is missing. You should at least connect some resistors similar to the disconnected stuff.