A Simple High Efficiency S.I. Engine Design 2003-01-0923
A method is described which permits the design of a four stroke, spark ignition engine to an expansion ratio arbitrarily greater than the compression ratio, and the operation of this engine at WOT at all but the lowest power outputs. A test engine employs modified fixed intake valve timing, an intake manifold with a reed valve, plenum, and plenum control valve, and reduced cylinder clearance volume. An independent laboratory compared the test engine to an unmodified stock engine at equal power. The test engine demonstrates a BSFC advantage (up to 36% at idle) when compared to the stock engine at partial throttle.