Another question would also be what’s the difference between wheel speed and vehicle speed?
In: 620
Engine RPM * Transmission Ratio * Diff Gear Ratio = Wheel RPM
Wheel RPM * Pi * Tire Height (with unit conversions) = Vehicle Speed
There are 4 main types of speedometers:
* Cable driven, from a worm gear in the transmission tailpiece (must be sized appropriately for final gear ratio). The speedometer itself is a magnetic clutch, and the faster you spin the input shaft, the higher the needle reads.
* Electronic speed sensor (basically an encoder that counts revolutions usually at the transmission). Some operate by resistance drop, others provide encoder feedback (analog signal) back to an ECU or gauge.
* Simple ECU calculated by engine rpm by ignition system count and known transmission speed/position
* GPS
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