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4

Manufacturers deliberately calibrate their speedos incorrectly. They make sure the speedo always reads higher than the actual road speed, and there is a very good legal reason for this. Speedometers must never read lower than the actual speed (European law (ECE-R39) says speedometers cannot show speeds less than the actual speed. Other countries have ...


5

Most speedos in the dash for modern electronic based cars, have a sensor in the output shaft of the transmission. It is a simple reluctor wheel and Hall effect sensor, or a gear driven motor which can then produce a signal for the PCM to interpret. Cars can also use the same method off of the anti-lock wheel sensor to get a "speed" indication. The more ticks ...



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