WET SUMP - conventional 4 stroke lubrication
NO VALVE GEAR
LOW THERMAL LOADING OF PISTON
LOW EMISSIONS WITH DURABILITY
LOW MANUFACTURING COSTS
COMPACT LOW MASS DESIGN
EXTENDED OIL CHANGE PERIODS (Oil does not degrade)
FAST WARM UP (lower cold start emissions)
ABILITY TO OPERATE ON A WIDE RANGE OF FUELS (including GAS)
Piston mass is naturally higher for a stepped piston design. However our unique approach means that for identical power cylinder bores the stepped piston is only around 20% heavier than a conventional looped scavenged two stroke piston. The multi section or step of the piston provides a flange stiffening effect resulting in thinner skirt sections. If necessary the mass increase can be reduced to below 15% by composite methods. However the engine uses the two stroke cycle and therefore with the absence of load reversals piston mass is not as critical as it is for four stroke engines. The Hooper stepped piston also provides improved load bearing and guidance resulting in low ring wear and reduced piston noise.
Designed and developed under MoD contract, this 580 cm3 four cylinder engine produces 35.4kW (47.5BHP) at 5250 RPM. The V4 configuration offers exceptional smoothness with NVH characteristics similar to a V8 four stroke engine. Gasoline and kerosene AVTUR / JET A-1 versions have been developed. The 30kW target performance was achieved with simple exhaust system and a very low engine mass of 18.2kg (air-cooled) or 18.5kg (liquid-cooled).
For further information on the stepped piston engine (sometimes also known as the stepped engine or step piston engine) or contract design and development of conventional 2 and 4 stroke engines and test rigs, see linked pages or contact BHE:-
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