Wireless remote control system for engine piston with in-piston circuit (50) and an external processing unit mounted on the exterior of the crank case (51). A carrier signal generated in the external processing unit is fed to a primary coil (P) located within the crank case and the secondary coil (S), loosely coupled to coil (P) and tuned for resonance therewith is located in the skirt of the piston. The secondary coil picks up a carrier signal from the primary coil and the carrier signal is rectified, smoothed and regulated to provide DC power to a micro controller in the piston circuit. The micro controller may use data from a number of sensors to modulate the signal in the secondary coil, which modulation is picked up by the primary coil and thus sensor data is transmitted to the external processing unit where it is filtered and decoded.