A system for controlling a variable compression ratio in an engine is provided. The system includes a cylinder, an outer piston located inside the cylinder, the cylinder and the outer piston collectively defining a combustion chamber, an inner piston, variably positioned inside the outer piston, the outer piston and the inner piston collectively defining an auxiliary chamber, a connecting rod including an air duct in fluid communication with the auxiliary chamber, and a crankshaft including an air passage in fluid communication with the air duct of the connecting rod during at least a portion of an engine cycle.