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Posted by Sheryll Alexander Jun 20, 2006 |
: The West Australian
(The diesel engine) is named after German engineer Rudolf Diesel, who received a patent for his invention in 1893 and demonstrated it at the 1900 Exposition Universelle in Paris using peanut oil as fuel.
The air-fuel mixture in the diesel engine is compressed to such high pressures in the combustion changer that it self-ignites, firing the engine without the benefit of spark plugs and an ignition system.
To achieve this, the diesel engine requires a compression ratio up to double that of a typical petrol engine.
Because the oil-like diesel fuel is rich in energy and requires less effort to start the combustion process, each power stroke provides more propulsion in the form of torque. This means that the engine generally uses less fuel.
High-compression diesel engine parts are heavier than those of lower-compression petrol engines, so the diesel engine spins more slowly.
Production diesel cars appeared in the mid-1930s, the models including the Mercedes-Benz 260D, Hanomag Rekord and Citroen Rosalie.
Turbodiesel development was encouraged by the 1970s oil crisis, the first production cars appearing late in the decade. These included the Mercedes 300 SD and 300 TD, and the Peugeot 604.
The first direct-injection turbodiesels - including the Fiat Croma, Austin Rover Montego and Audi 100 TDI - were launched in the late 1980s.
The Audi 100's pioneering electronic control of the engine allowed big gains in emissions reduction, refinement and power.
In recent years, new technologies have made major steps towards these goals.
One direction has been common-rail injection, which does away with pump injectors and replaces them with a central storage "rail', or tube, where the fuel is kept under extreme high pressure and then released via precise, electronically controlled solenoid injectors directly into each cylinder.
The high pressure creates a fine mist of fuel for more efficient burn.
Electronics also allow the process to be broken down into a series of smaller injections to improve combustion for cleaner, quieter and more efficient firing.
Most modern turbodiesel engines provide frugal fuel use, long tank ranges, quiet operation, lots of grunt and low emissions, especially where particulate filters are fitted.
Downsides include the higher cost of diesel fuel, inadequate facilities at many service stations and the higher initial purchase cost of the car, though the discrepancy is narrowing.
From a low base, sales of turbodiesel passenger vehicles in Australia have rocketed in the past two years.
In the first five months of this year, sales of private passenger diesel cars were 3045, a 93.5 per cent lift on the same period last year.
Sales of non-private passenger diesels jumped 218 per cent.
Brands such as Peugeot, Volkswagen, Mercedes-Benz, Audi and BMW are moving towards offering diesel variants across their ranges.
Citroen, Jaguar, Chrysler and Alfa Romeo have also recently released diesel models and the coming Fiat Punto will be offered with a turbodiesel model.
Most 4WD brands offer turbodiesel models, with only the compact segment awaiting a reasonable selection.