US Patent 7438028 Four stroke engine with a fuel saving sleeve

A four stroke engine with piston strokes all of equal length whereby the intake stroke displacement and the compression stroke displacement are smaller than the expansion stroke displacement and the exhaust stroke displacement. This is accomplished using the fuel saving sleeve that has a projection on one end. A magnetic force is used to keep the fuel saving sleeve at the top of the engine cylinder during the intake and compression strokes. This makes the sleeve act as an air displacer during the intake and compression strokes. The projection transfers the pressure of burning gases on the sleeve to the piston during the expansion stroke. It also transfers force from the piston to the sleeve during the exhaust stroke. This makes the sleeve act as an enlargement of the piston during the expansion and exhaust strokes.