tech question... how well do you know motronic?

[mspiegle]

i have an '87 325is with a #173 box. I hooked up an SMT6 to do some fuel/ignition tuning.

The SMT6 tunes fuel by modifying the AFM signal. I know AFMs work on a 0-5v range, but what happens when motronic gets a signal that is over 5v? It sends out a check engine light and something else...

I notice that when the SMT6 modified the signal so much that it's going over 5v, the car seems to lose power and the check-engine light comes on. Does anyone know what motronic is doing when this happens?

[Red325es]

No computer should ever see more than 5 volts ( this was stressed in my advanced electrical class) even your household computer only operates off of 5 volts!

[PeterCip]

your concfusing the motronic and it goes into panic mode..symptoms of this are widlbucking, or loss of power in the form of hesitation..
ask me how i know

[EVOIIIM3]

If you go outside of the parameters the ECU goes wild, it does not have any code for that signal and it will freak out.

Not only do you have to keep the voltage right, but you have to do it with the proper RPM. The signal will change with RPM, and if they fall outside of the map you can not only loose power, but the engine if you go to lean, the other side is going to rich and leaning out the oil with fuel and then spin a bearing.