The Wave Engine is a four cycle engine which was developed to use an Atkinson Cycle to dramatically improve the thermal efficiency. In an Atkinson Cycle engine the engine's expansion ratio is greater than the compression ratio. This over-expansion allows the engine to utilize more of the combustion pressures to produce power, thus reducing energy lost through the exhaust system and improving the thermal efficiency.
The engine's over-expansion also allows for the cylinder temperatures to be dramatically reduced at the end of the expansion stroke. The over-expansion will thereby reduce the average combustion temperatures during the entire engine cycle which will reduce the amount of energy transferred to the coolant and oil.
The design of the Wave Engine is such that the piston connecting rod remains completely vertical during the entire engine cycle. Because the connecting rod has no angularity during the cycle there will be very little side loading of the piston into the cylinder liner. By reducing the piston side loading there will be a significant reduction in the friction losses between the cylinder and piston.