A Simple Variable Expansion-Ratio, Spark Ignition, Four-Stroke, Engine

A description is given of a new form of Otto-Atkinson type engine, which does not incorporate variable valve timing, in which the compression ratio is essentially invariant over the full range of operating conditions. A brief review of relevant thermodynamic considerations precedes a discussion of the mechanical aspects of the proposed engine. This is followed by performance predictions. It is shown theoretically, with support from experimental work by others, that the new engine offers the promise of fuel savings of about 21-24% at 30% of full load and of 10% at 80% of full load.