Drive by wire throttle control - need to develop stand-alone controls

[Sweeper]

Hi Everyone,

I am working on an engine transplant from a 2003 BMW to an older, pre-OBDII car. Due to the extensive vapor recovery system and emissions controls required by the original engine management system, I have decided to replace it with an aftermarket unit (Electromotive Tec3, for those interested).

I am currently having difficulty adapting the drive-by-wire throttle system. The system was designed to use a standard 5V potentiometer in the gas pedal (like many engine sensors), which the DME would interpret into a signal for the stepper motor controlling the throttle plates. Since the DME is no longer present, I need to create a new "middle-man", of sorts.

I initially thought of treating the gas pedal potentiometer as a TPS, and creating a 3D map of load and TPS vs. throttle opening. However, the Tec3 does not have the ability to handle this.

Right now, I think my best bet is to buy or build a controller that can scale a 5V potentiometer input to a stepper motor output. I would probably prefer buying to building, but I did expect that there would be some learning experiences on this project.

If anyone can lead me down the right path, or point me to a controller that will do what I need, that would be great.

I hope no one will mind if I cross-post this to one of the EE forums.

thanks,
- -Matt

 

[Andy330hp]

Since you're removing all the factory controls, why not remove the electronic throttle? Are there any throttle bodies you could purchase from a slightly earlier BMW that is a standard cable throttle, but would bolt in place of your current one? It certainly would simplify things, and there's no real advantage to keeping electronic throttle if you don't have an ECU that can take advantage of it.

 

[Flowczar]

Pitch the electronic throttle like Andy suggested. Since your ECU cannot handle the system, and I can't think of anything worse than a "stuck" throttle, evaluate the risks and make a sensible decision.