The origin of modern day four-cycle internal combustion engines is the Otto cycle. Invented by Nikolaus August Otto in 1876 the four-stroke reciprocating engine provided an effective way to convert combustible fuels into useful mechanical energy.

There are, of course, other approaches such as the Wankel or two-cycle engine but these are less efficient than the Otto cycle and have greater exhaust pollutants. The Diesel is an effective engine that approaches the Stirling cycle in efficiency but is generally heavy and quite noisy.

Stratified charged engines have promise of very low exhaust pollutants but to date are not in general use. Its operational feature is a dual combustion chamber with a pre-chamber that receives a rich fuel-air mixture while the main chamber is charged with a very lean mixture. With ignition of the rich mixture, that in turn ignites the lean main mixture, results in combustion that does not foster formation of nitrogen oxide and carbon monoxide pollutants.

The principal four stroke Otto cycle functions are the piston downward stroke with intake of fuel and air, followed by the upward compression stroke. Ignition of the compressed gas for the downward power stroke is then, followed by the fourth upward exhaust stroke.

Reciprocating engines suffer a major loss in efficiency with piston direction change. The changes in piston mass velocity subtract directly from the energy product of the expanding gas and engine out put torque.

The Trochilic Quad cycle engine uses a split segment piston with an associate gear cage to circumvent this problem. With the trochilic piston, deceleration of one segment translates to acceleration of the other segment and the sequence is reversed every quarter cycle. The net result is a near zero loss of energy from piston velocity changes in rotation.

Poor efficiency is also rooted in waste engine heat conducted away by a cooling radiator that does not contribute to engine torque. With Trochilic Quad cycle engines, piston to cylinder contact is not in evidence; therefore, the cylinder is insulated to prevent heat loss. In addition, internal surfaces are coated with ceramics to retain engine heat within the working gas; therefore, boosting efficiency too.