Hi!

Iv got problem with my 2003 Celsior. At 60 mph on speedometer I get 40 mph on GPS. Car is on 20 inch wheels but the difference between readings is too big in my opinion to be caused only by the wheel diameter. Where to look for the problem? Speed sensor, speedometer it self? Car is Japanese import. Readings of speed are very smooth without any pikes or something, just the value is way off the real one.

Thanks, Jan. 

 

Yes, we only use km/H in Japan or most of countries. Only UK and US use the good old mile system. 40miles/H is 64.36km/H since 1mile = 1.609km.
If I were to use a Celsior in US, I would make and add a divider circuit using a FPGA to the meter's pulse circuit.