Primary-secondary induction internal combustion engine

A four stroke Otto Cycle cylinder and piston engine having dual range low and high speed performance, and including;

• a head closing the upper end of a cylinder and establishing a chamber in which a piston reciprocates by means of a crank and rod connection between top-and-bottom-dead-center positions, a primary working fluid induction means operating in timed relation to both low and high engine speed and comprising an intake valve in the head and fuel-air admixture means open therethrough during the intake stroke, and exhaust means operating in timed relation to both low and high engine speed and comprising an exhaust valve in the head and a stack open therefrom during the exhaust stroke, and secondary working fluid induction means comprising a port opening into the cylinder chamber and with its upper extremity substantially midway between top-and-bottom-dead-center positions of the top of the piston and with its lower extremity at said bottom-dead-center position thereof, and resonant check valve means biased to remain closed at low engine speed and resonant to open said port intermittently in timed relation to high engine speed for the efficient induction of secondary working fluid through said port from fuel-air admixture means and into the cylinder at a tuned frequency of movement of the top of the piston between said top-and-bottom-dead-center positions thereof when uncovering said port for said induction.