Tour Engine Inc. patented a revolutionary inherently efficient design. Unlike current IC engines that use the same cylinder for all four strokes, TourEngine™ is designed to have two cylinders opposing each other that divide the traditional four stokes between them. 
This revolutionary design provides means to reduce the two big energy losses in common internal combustion engines - heat loss to the radiator coolant and exhaust thermal loss.
In the TourEngine™ design the two cold strokes, Intake and Compression, occur in one relatively Cold-Cylinder, (left side in the figure) while the hot strokes, Combustion and Exhaust, occur in a different cylinder that is hotter and bigger (Hot-Cylinder, right side in the figure). In this configuration, the cold and hot strokes occur in parallel in the two cylinders.
A special crossover valve governs the precisely timed transfer of the compressed charge from the Cold-Cylinder to the Hot-Cylinder. The head-to-head configuration permits the direct coupling of the Cold and Hot cylinders and eliminates the need for a connecting tube. The absence of a connecting tube ensures minimal pressure loss and the dynamic and efficient transfer of the complete compressed charge between the Cold and Hot cylinders.