Mechanism

This section is for technically minded readers and explains in simple terms how the Energy Storage Piston works without and with compression ratio doubling.

Without compression ratio doubling

Assume the piston is rising on the compression stroke initially, the spring compresses proportionately to the compression load.  However after the ignition has comlpeted, the spring compresses completely (assuming full load). The spring has been designed to give full deflection at full load such that the clearance volume height doubles. The doubling of the clearance volume height causes the combustion pressure to approximately halve; thus the spring "loads up" to an upward force equal and opposite to the combustion force. The lower cylinder pressure and the force stored in the spring now combine to give the output torque.

The halving of the cylinder pressure also approximately halves the temperature, thereby reducing the heat lost to the cylinder walls and exhaust.

As this heat loss accounts for approximately 60% of the energy generated by combustion of the compressed vapour half of this loss will be saved, and therefore the output torque is proportionately greater than it would have been had the spring not been present.

Thus the reduction of the energy loss to the cylinder walls and to the exhaust is available for output torque. 
This gives an efficiency increase of approximately 30% and a similar reduction in exhaust emissions.

With compression ratio doubling

The doubling of the compression ratio causes the compression ratio of the Energy Storage Piston to return to that of a standard piston, after ignition has taken place and the spring is fully compressed. The pressure and therefore heat losses will then be the same as a standard engine in the same circumstances, but the spring will be loaded with half the energy as a result of the combustion. This spring energy is not lost to the cylinder walls, as it has been converted into strain energy in the spring, and is now available for output torque.

The engine therefore behaves as a standard engine that has had its compression ratio doubled but without the inevitable problems that this would cause, for example, "pinking". This increase in output energy, compared with a standard piston, results in an increase in efficiency from the engine, producing more miles per gallon hence fewer emissions per mile.

In this case a driver of a vehicle fitted with Energy Storage Pistons would have to throttle back to achieve the same speed as a standard piston engine, causing the exhaust emissions to reduce proportionately.