A timepiece includes a light emitting device for generating a light, and one or more rotary wheels having one or more light receiving orifices, and one or more reflective members attached onto the sides of the rotary wheels for reflecting the light generated by the light emitting device and emitted through the orifices of the rotary wheels. According to one aspect of the present invention, values are stored in a square look-up table for determining the square of a value. The method includes providing an engine command; calculating a desired cylinder charge based on said command; and adjusting the outlet control device to provide said desired cylinder charge.