Modern Usage
The sleeve valve has begun to make something of a comeback, due to modern materials, dramatically better engineering tolerances and modern construction techniques, which produce a sleeve valve that leaks very little oil. However, most advanced engine research is concentrated on improving other internal combustion engine designs, such as the Wankel.
Mike Hewland with his assistant John Logan, and also independently Keith Duckworth experimented with a single-cylinder sleeve-valve test engine when looking at Cosworth DFV replacements. Hewland claimed to have obtained 72 hp (54 kW) from a 500 cc single-cylinder engine, with a specific fuel consumption of 177 gr/HP/hr — 0.45 to 0.39 lb/hp/hr-, the engine being able to work on creosote with no specific lubrication supply for the sleeve, just the sleeve driving mechanism requires a specially devoted lubrication, and a lubricating oil use half of the poppet-valve engines of its time. Hewland reported also that the highest temperature measured in the cylinder head didn't exceed 150° C, sleeve temperatures were around 140° C, Temp. was 270° C in the center of cylinder and 240° C at the edge, and having raced the engine up to the region of 10'000 rpm.
A SAE paper from 2003 deals with a high-speed, small-displacement sleeve-valve engine, calculated, but not experimentally shown, to have a higher SFC than the poppet-valve alternative, a year-2009 work compares two different side-opening intake strategies for sleeve-valve engines.
An unusual form of four-stroke model engine that uses what is essentially a sleeve-valve format, is the British RCV series of "SP" model engines, which use a rotating cylinder liner driven through a bevel gear at the cylinder liner's "bottom" and, even more unusually, have the propeller shaft — as an integrally machined part of the rotating cylinder liner — emerging from what would normally be the cylinder's "top" at the extreme front of the engine, achieving a 2:1 gear reduction ratio compared to the vertically oriented crankshaft's rotational speed. The same firm's "CD" series of model engines use a conventional upright single cylinder with the crankshaft used to spin the propeller directly and also use the rotating cylinder valve. As a parallel with the earlier Charles Knight-designed sleeve-valved automotive powerplants, any RCV sleeve-valved model engine that is run on model glow engine fuel using castor oil as a small percentage (about 2% to 4% content) of the lubricant in the fuel allows the "varnish" created through engine operation to provide a better pneumatic seal between the rotating cylinder valve and the unitized engine cylinder/head castings, initially formed while the engine is being broken in.
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