IN DISHEVELLED Second World Warbuildings in the countryside west ofBirmingham, UK, Bernard Hooper isworking through the problems of developing a new diesel engine for small carsfor the 21st century. He is trying todevelop a 2-stroke engine with a steppedpiston design which would achieve lowexhaust emissions and low fuel consumption but high durability with nodiminution in performance for the newgeneration ultra-small, lightweight cars.
Hooper believes that the contemporary small, high revving, 4-stroke dieselengines fitted to cars will prove tooheavy and big for the new generationcars. These engines are heavier thantheir petrol counterparts because theirblock and cylinder head has to withstand chamber compression ratiosalmost double those of a petrol engine.
Add valves, camshafts and thecamshaft drive components needed onany 4-stroke engine, and it wouldrequire a genius to fit all these into thebonnet of ultra-small cars of the future-In addition, diesel engines are facingdifficulty in meeting the tighter exhaustemission standards planned for laterthis decade, which would inevitablyrequire the use of an exhaust catalyst. Hooper argues that all theseproblems can be overcome by the2-stroke engine with a'steppedpiston design, which he is trying to develop.
The stepped piston is asimple fabrication thatincludes a small number ofindividual components. It has2 diameters, the smaller beinga normal piston that is used inconventional 2-stroke engine.The larger diameter section atthe bottom of the piston actsas the compression piston. (see diagram)
The intake charge is drawn intothe annular space controlled by reedvalves, which close and open automatically. The intake is. charged throughtransfer ports into the combustionchamber of the other cylinder suckingin the exhaust gases in the process. Thiscontinues until the exhaust ports areclosed by the rising piston and the compression begins.
Hooper's technology might proveinteresting to car makers because of several reasons. One is the very fact that it is a 2-stroke engine - this dispenses withthe valve gear, its weight, size and otherassociated penalties. Second, Hooper'sengine provides twice as many firing strokes as a 4-stroke engine, thereby giving a smoother and a more powerful performance.
And finally, it is the Hopper's extraingredient - the stepped piston design - that could get over the age-old problem with the conventional 2-strokeengines, that is unacceptably high emissions of oxides of nitrogen. SaysHooper, "The Achilles heel of the 2stroke engine is that all fuel goes through the crank case. Since you carmcmseparate the lubrication from combustion, so the oil ends up in the exhaustThe stepped piston engine separates thelubrication from the combustion - thus reducing emission problems."
Hooper, formerly the chief designerwith the UK-based Villiers Engineering.is not the only one exploring alternativecombustion technologies and engineconcepts. But what makes Hooper different from others is the fact that he isamong the few who are trying to develop engines with a genuine comparativeadvantage over petrol and diesel units. The idea itself is not new. In fact, it dates back to the First World War years, but like many othef alternative engine concepts, it remained undeveloped for all these decades.