While the world is turning to hybrids, work is quietly continuing on developing a new petrol engine. The goal is to combine the best bits of petrol and diesel motors while negating the handicaps of both.
The means an engine with greater efficiency and range with a cleaner exhaust.
The technology — homogeneous charge compression ignition (HCCI) — has been around since the 1970s but until now only the trucking industry has taken it seriously. But car companies are revisiting the concept to as a way of reducing fuel consumption without the loss of power or performance.
It works by mixing petrol with air outside the combustion chamber, just like a conventional petrol motor. But the difference is that the gas is then compressed in the cylinder to produce heat which creates combustion — like a diesel - without the need for sparkplugs.
Mercedes-Benz, Toyota and Honda have all dabbled with the technology but General Motors in the United States is the latest car company to pick up the HCCI baton to try and bring the engine into production and has prototype cars running in both America and Europe. However the future of the project is now uncertain after General Motors filed for bankruptcy this week.
Until now there have been plenty of obstacles in developing the HCCI engine because the explosive combustion process has been difficult to control with any accuracy, especially under various speeds and engine loads.
The advent of microprocessors has solved part of that problem and GM says it still uses conventional spark plugs for cold starting before the spontaneous combustion takes over once the cylinders are brought up to temperature.
The beauty of HCCI system is that it compared to a conventional petrol engine it produces fewer noxious exhaust gases so it doesn't rely on expensive catalytic converters to reduce emissions. The system also overcomes the petrol engine's biggest handicap that up to 80 per cent of thermal energy created in the combustion process is wasted.
GM says an HCCI engine could come close to matching the efficiency of a typical hybrid engine at a fraction of the production cost.
GM claims to have achieved up to 15 per cent better fuel efficiency over a conventional engine with no substantial loss of performance and the system can work from idle right up to 100km/h.
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