Had my car on a dyno yesterday, and while the front wheels were spinning, I noticed the speedometer wasn't registering! Strange....could it be the speedometer gets its signal from the rear wheels? Every other FWD car I've had has the speed signal come from the front (specifically, the transmission). Where does the speed signal come from in a Mini?

 

That is weird. The speed signal comes from the ECU actually. There have been strange things that the dyno has done - I had a DSC light and one other light that I can't recall now at the same time on one of the first runs, then it dissappeared. I don't know if I've ever looked to see if the speedo was working...

 

Interesting indeed! Do you have to turn off the DSC to do a dyno-pull? Since the rear wheels aren't rotating at all, the computer is no-doubt "Freaking out"!

Randy, the signal for the gauge may come from the ECU or perhaps the BCM, but where is the sensor? Does the BCM "know" what gear you're in, and have a built-in table for "gear versus RPM equals speed?" With all the wheel sensors, the BCM also knows the wheel RPM (for the FTM), and could cross reference a programmed diameter tire with the engine RPM vs. tranny gear...... You could even detect clutch wear! COOOOOL! Do I smell a new aspect of DSC coming on, using the clutch as a torque reduction tool (or does BMW already do this?)