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Why change current engine designs? (Continued)
In 1995, Automotive Mechanical Engineer, Brad Howell-Smith was researching the internal combustion engine and its efficiency and losses. He found that if a typical engine’s Mean Effective Pressure map from the combustion cycle was simulated against a conventional crankshaft device, that the efficiency of that device was only 65% efficient.

For an example, at 10-30 degrees After Top Dead Centre (ATDC) when the pressure in the cylinder is at its highest, a crankshaft connecting rod arrangement provides low mechanical transfer to rotational force.
Most of the force is applied downwards on the main journals and is wasted as a mechanical loss. At between 70-80 degrees ATDC, the crankshaft mechanical device has high efficiency because the connecting rod is around 90 degrees to the crank.

At the crankshaft’s point of highest efficiency, the piston has travelled approximately 40% down the stroke, and the pressure in the cylinder is around half of peak. This interesting finding meant that the formula for working out engine losses must include the mechanical losses caused by the poorly efficient crankshaft device. It is believed that all losses have been accounted for in the formula.

The Dream of an Engine
After the theory was realised, Brad literally dreamt the Revetec engine design. After graphing the performance of the new engine design, it was realised that it is possible to increase an engine’s efficiency to a much higher level. In some initial designs it was calculated that a petrol engine of this design could reach 50% efficiency, which is deemed as unachievable in the industry.

Breaking the Theory
Over the last decade, six different versions of Revetec engine designs have been prototyped. The latest version was designed as a development engine for the aviation industry, and in early 2008 it was independently tested by Orbital Australia. The X4v2 engine has a very basic top end featuring only two valves per cylinder operated by push rods. It features no variable valve timing nor variable length intake ports which are common in many current late model vehicles.

The X4v2 Prototype petrol engine achieved a Brake Specific Fuel Consumption (BSFC) of 207g/(kW-h) or 39.5% efficiency. The figure achieved was deemed as impossible, given the knowledge of engine losses and that various current engines achieve an efficiency in the range of 27-32%.
Copyright Revetec Holdings Limited 2009