A California company says its radical design for an internal combustion engine could increase efficiency and cut greenhouse gas emissions.

The San Diego firm Tour Engine says it has a solution: Just split the engine in two, NewScientist.com reported Wednesday.

Conventional engines convert just 30 percent of available energy into motion because of a design compromise between two conflicting stages, or strokes, of their cycle: compression and combustion.

To efficiently compress the air and fuel drawn into the engine, its cylinders need to be cool, so a radiator has to constantly draw energy in the form of heat away from the cylinders. But that reduces the amount of heat energy available to push the pistons and move the car.

Tour Engine's design splits the engine cylinder into two separate but connected halves -- one cold and one hot -- connected by a valve. The cold half of the cylinder houses the intake and compression stages of the cycle, while the hot half carries out the combustion and exhaust stages.

Separating them allows the size of each to be better suited to their very different tasks, Tour Engine says.

In a conventional engine, the cylinder is smaller than is desirable for the combustion stage because smaller means more efficient compression.

This, however, means the burning air-fuel mixture does not have enough space to expand fully, so a substantial amount of energy is simply lost as heat through the exhaust pipe.

"In conventional engines you lose about 40 percent of the available energy to the cooling system, and about 30 percent to the exhaust," Tour Engine says.

The company says its split cylinder design could increase efficiency by 50 percent.