Abstract: A two-stroke internal combustion engine has at least one cylinder having a bore diameter, a piston slip-fit in the cylinder, the piston having an upper portion and a lower portion and a central portion of significantly less than the bore diameter, providing an annular space between the central portion and the cylinder wall, and an air pump providing air to one or more intake ports, wherein for a significant portion of every stroke both one or more exhaust ports and the one or more intake ports are open to the annular space between the central piston portion and the cylinder wall, allowing the air pump to force air from the one or more intake ports around the central piston portion to the one or more exhaust ports.

Abstract: A two-stroke internal combustion engine has at least one cylinder having a bore diameter, a central axis, a cylinder wall, and an upper and a lower extremity, a piston slip-fit in the cylinder, the piston having an overall height and a top surface, an upper portion and a lower portion each of approximately the bore diameter, each of the upper and lower portions having at least one seal ring between the piston and the cylinder wall, and a central portion of significantly less than the bore diameter and a height at least one-half of the overall piston height, providing an annular space between the central piston portion and the cylinder wall, a crank mechanism coupled to the piston in a manner providing a repeating stroke of a specific stroke length in the direction of the central axis of the cylinder, the repeating stroke providing a varying volume V between the top of the cylinder and the top surface of the piston, one or more exhaust ports through the cylinder wall, each exhaust port having a first height in

Abstract: A method for managing oil temperature for a vehicle engine comprises the steps of (a) determining a preferred temperature window for oil in operation of the vehicle, comprising a first, lower temperature, and a second, higher temperature; (b) pumping oil from the vehicle engine to a control valve controlling oil passage into a radiator, and bypassing the radiator via a by-pass passage in the control valve more than seventy-percent of the oil to return to the vehicle engine without passing through the radiator upon cold start-up; (c) closing the bypass passage at the first oil temperature, forcing all oil entering the control valve to pass through he radiator before returning to the vehicle engine; (d) starting a forced-air fan at the second temperature to urge ambient air through air passages of the radiator, thereby enhancing ability of the radiator to cool the oil passing though; and (e) as oil temperature falls, opening the bypass passage again at the first temperature.