Wheel Sensor Output for Rally Computer
 

Howdy, folks. I'm trying to install a rally computer in my 1997 C36 AMG and am hoping someone can help me. Essentially, the rally computer is a hyper-accurate odometer that uses a pulse from a distance sensor to tell you precisely how far you've gone and what your average speed was over some selected elapsed time and/or distance. Typically, the distance sensor consists of a Hall-effect sensor mounted near a rotating part of the drivetrain on which rare-earth magnets are mounted. Whenever a magnet comes by the sensor, it triggers a pulse and lets the computer know that a revolution (or fraction therof) has been completed. Putting the computer into calibration mode then running a known distance, the computer determines a "factor" for how many pulses make up the known distance.

I've installed a computer on our rally car (1984 190E 2.3/5 speed) using this method, but I'd rather not epoxy any magnets to my AMG wheels nor drill any holes in my firewall. I know that the ABS system uses sensors on each wheel, and was hoping to piggyback an input to the computer from somewhere inside the passenger compartment. Suggestions, anyone?

The drive shaft is an easy place to get that info from if add a magnet & pick-up.

The traction system is complex & if you decide to TAP into that info, I would suggest adding a diode so that there wouldn't be any feedback from your rally computer into the traction system computer.

Thanks for the reply, Doc, but I was hoping to tie into the existing sensor system somewhere within the passenger compartment so that I won't have to add any magnets or drill any holes in the body. Adding a diode or even a buffer amplifier will be a piece of cake for me, but I need to know where to get the wheel sensor output from the wiring harness inside the car.