Wheel Sensor Output for Rally Computer - PeachParts Mercedes-Benz Forum

RobertFini · #1 11-03-2003, 02:35 PM

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?

mbdoc · #2 11-03-2003, 03:10 PM

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.

RobertFini · #3 11-03-2003, 04:39 PM

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.