i'm not measuring yet, i calculated the time frame according to wheel diameter x pi, so when i,m drivind 100km/h the wheel revolutions are 51340rev/hr equals 14,26 rev/sec equals app. 70 msec/rev.
but the calculation is not the problem, its making the arduino understand how to measure the time between the pulses so that i can compare it with my setpoint and control the throttle with a pwm output and a simple pid sketch