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THEORY OF OPERATION The major advantages of a GDI engine are increased combustion, Stoichiometric combustion and high power output mode. Each mode is characterized by air-fuel ratio, the amount of fuel in the air-fuel mixture; the stoichiometric ratio for Petrol is 14.7 to 1 by weight, but in ultra lean mode, it could be as high as 65 to 1. These leaner mixtures than those ever achieved in the conventional engines are desired because of reduced fuel consumption.
Direct injection can also be accompanied by traditional methods such as VVT and VLIM , which provide conventional control over airflow swirl patterns at stoichiometric and full power modes. Water Injection or EGR can help reduce NOx emissions inevitable when burning Ultra Lean mixtures. HISTORY The 1955 Mercedes-Benz 300SL , the first gasoline-powered automobile to use Fuel Injection , used direct injection. The Bosch fuel injectors were placed into the bores on the cylinder wall used by the spark plugs in other Mercedes-Benz six-cylinder engines (the spark plugs were relocated to the cylinder head). Later, more mainstream applications of fuel injection favoured less expensive indirect injection methods. It was not until 1996 that gasoline direct injection reappeared on the market. Mitsubishi Motors was the first with a GDI engine in Japan, the Galant / Legnum 's '' 4G93 '', which it brought to Europe in 1998 . Mitsubishi applied this technology widely, producing over 400,000 GDI engines in four families before 1999, but high-sulphur fuel led to emissions problems, and Fuel Efficiency was less than expected. PSA Peugeot Citroën also launched a GDI engine (with licensed Mitsubishi technology) in 1999, but both were withdrawn from the market in 2001 . DaimlerChrysler produced a special engine for 2000 , offered only in markets with low sulphur fuel. Later GDI engines have been tuned and marketed for their high performance. Volkswagen / Audi led the trend with their 2001 GDI engine, under the product name Fuel Stratified Injection (FSI). The technology, adapted from Audi's Le Mans racecars, induces an electric charge in the fuel-air mixture. BMW followed with a GDI V12 . PSA is cooperating with BMW on a new line of engines for future introduction. General Motors had planned to produce a full range of GDI engines by 2002 , but so far only two such engines have been introduced - in 2004 , a version of the 2.2 L Ecotec used by the Opel Vectra and in 2005 , a 2.0 L Ecotec with VVT technology for the Pontiac Solstice GXP . Toyota 's '' 2GR-FSE '' V6 will use a combination of direct and indirect injection in 2006 . It uses two injectors per cylinder, a traditional port injector and a new direct injector. Mazda uses their own version of direct injection in the new Mazdaspeed 6 / Mazda 6 MPS. It is referred to as Direct Injection Spark Ignition. Isuzu offered a direct injection 6 cylinder engine in the 2004 Axiom and Rodeo, and both were the least expensive direct-injection models offered in the United States from then until present (April 2006). EXTERNAL LINKS
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