Reading motor CAN bus data

Hello everyone,

My name is Michael, I'm 30 years old, and I work as an electrician. To be honest, I don't know much about the CAN bus system yet.

I drive a BMW e92 with the n54 engine. Since I'm experiencing some issues with the intercooler during the summer, I would like to install a water injection system. While there are several versions available, most of them won't work for me, and the others don't meet my requirements in terms of control and functionality.

My idea is to read a set of motor parameters from the motor's CAN bus, use these parameters to calculate the fuel injection amount, and then generate a frequency-based signal that uses this calculated value as input for controlling the water injection system.

My question: What hardware is best for me to start with? I obviously only need read-only access to the bus. It would also be good if I could connect a small display to show the values being read and, later on, the calculated values in real-time while driving.

Thank you in advance for your help.
Best regards,
Michael.

Hello,

With a bit of luck, you'll find the intake air temperature data on the powertrain CAN bus, which you should check. For experimentation, I recommend using a forum-specific CAN interface and then an Arduino or similar device to control your water injection system.

Best regards, Rainer.

Good morning.

The intake air temperature wouldn't be that important, or rather, it's just one of the parameters I would like to have. I could also make it available as an analog signal in an emergency, but it would obviously be easier if everything was available on the bus. Overall, I was thinking about the following parameters: engine speed, boost pressure, intake air temperature, and outside temperature. It would be nice to also have the calculated air mass and throttle position.

How difficult is it to find the data on the bus? Or rather, how easy is it to determine which value corresponds to which ID?

Best regards,
Michael.

If you don't have the appropriate communication matrix, it will be very difficult. Some data might potentially be requested via a diagnostic request over CAN, but that would likely be too slow for a water injection system.