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THEORY OF OPERATION The major advantages of a GDi engine are increased Fuel Efficiency and high Power output. This is achieved by the precise control over amount of fuel and injection timings which are varied according to the load conditions. In addition, there are no throttling losses when compared to a conventional Fuel Injected or Carbureted engine, which greatly improves efficiency in engines without a throttle plate. The , Stoichiometric , and full power output. Each mode is characterized by the Air-fuel Ratio . The Stoichiometric air-fuel ratio for Petrol (gasoline) is 14.7 to 1 by weight, but ultra lean mode can involve ratios as high as 65 to 1. These leaner mixtures, much leaner than in a conventional engine, reduce fuel consumption.
Direct injection may also be accompanied by other engine technologies such as Variable Valve Timing and tuned or Variable Length intake manifolding. Water Injection or (more commonly) Exhaust Gas Recirculation can help reduce the high NOx emissions that result from burning Ultra Lean mixtures. HISTORY The first direct injection system was developed by Bosch , and was introduced by Goliath and Gutbrod in 1952. The 1955 Mercedes-Benz 300SL , the first sports car 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. During the late 1970's, the , '' Car And Driver '', June 2004 utilizing a unique high pressure pump and direct injectors. One hundred Crown Victoria cars were built at Ford's Atlanta Assembly in Hapeville, Georgia utilizing a ProCo V8 engine. The project was canceled for several reasons; electronic controls, a key element, were in their infancy; pump and injector costs were extremely high; and lean combustion produced Nitrogen Oxides in excess of near future EPA limits. Also, the three way Catalytic Converter was proven to be a more cost effective solution. It was not until 1996 that gasoline direct injection reappeared in the automotive market. 1999 DaimlerChrysler produced a special engine for 2000, offered only in markets with low sulphur fuel. Although other companies have since developed gasoline direct injection engines, GDI (with an uppercase final "I") remains a registered trademark of Mitsubishi Motors. "GDI-ASG Pistachio" , Mitsubishi Motors press release, September 28 1999 Toyota introduced direct injection engine D4 ( Toyota AZ Engine ) in 2000 Toyota Avensis . Toyota 's '' 2GR-FSE '' V6 uses a combination of direct and indirect injection. It uses two injectors per cylinder, a traditional port injector and a new direct injector. Later GDi engines have been tuned and marketed for their high performance. Volkswagen / Audi introduced their GDi engine in 2001, under the product name Fuel Stratified Injection (FSI), the technology adapted from Audi's Le Mans prototype racecar. Alfa Romeo introduced their first direct injection engine JTS in 2002, and today the technology is used on almost every Alfa Romeo engine. BMW introduced GDi V12 BMW N73 engine in 2003. This initial BMW system used low-pressure injectors and could not enter lean-burn mode, but the company introduced its second-generation High Precision Injection system on the updated N52 Straight-6 in 2006. This system surpasses many others with a wider envelope of lean-burn time, increasing overall efficiency.1 PSA is cooperating with BMW on a new line of engines which will make its first appearance in the 2007 MINI Cooper S . 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 , the Vauxhall GT, the Opel Speedster, and the Saturn Sky Red Line. The forthcoming 2008 Cadillac CTS and Cadillac STS will also be available GDi 3.6 L LLT engine due out in the fall of 2007. In 2004 Isuzu Motors produced the first GDi engine sold in a mainstream American vehicle. Standard on the 2004 Axiom and optional on the 2004 Rodeo. Isuzu claimed the benefit of GDi is that the vaporizing fuel has a cooling effect, allowing a higher compression ratio (10.3 to 1 versus 9.1 to 1) that boosts output by 20 horsepower and that 0-to-60 times drop from 8.9 to just 7.5 seconds, with the quarter-mile being cut from 16.5 seconds to 15.8 ticks. "Isuzu Direct-Injection V6" , ''Popular Science'', 2003 Mazda uses their own version of direct injection in the Mazdaspeed 6 / Mazda 6 MPS, the CX-7 sport-ute, and the new Mazdaspeed 3. It is referred to as Direct Injection Spark Ignition. IN TWO-STROKE ENGINES The benefits of direct injection are even more pronounced in Two-stroke engines, because it eliminates much of the pollution they cause. In conventional two-strokes, the exhaust and intake ports are both open at the same time, at the bottom of the piston stroke. A large portion of the fuel/air mixture entering the cylinder from the crankcase through the intake ports goes directly out, unburned, through the exhaust port. With direct injection, only air comes from the crankcase, and fuel is not injected until the piston rises and all ports are closed. Two types of GDI are used in two-strokes: low-pressure air-assisted, and high pressure. The former, developed by Orbital Engine Corporation of Australia (now Orbital Corporation) injects a mixture of fuel and compressed air into the combustion chamber. When the air expands it atomizes the fuel into 8- Micrometre droplets, very small relative to the 20 to 30-micrometre fuel droplets in other direct injection systems. The Orbital system is used in motor scooters manufactured by Aprilia, Piaggio, Peugeot and Kymco, in outboard motors manufactured by Mercury and Tohatsu, and in personal watercraft manufactured by Bombardier. In the early 1990s, Ficht GmbH of 1996 OMC purchased a controlling interest in Ficht in 1998."Marriage Made in Boat Heaven", '' Sarasota Herald-Tribune '', December 26 1998 Beset by extensive warranty claims for its Ficht outboards, OMC declared bankruptcy in December of 2000 and the engine manufacturing portion and brands ('', March 26 2001 , http://findarticles.com/p/articles/mi_m0BQK/is_2_6/ai_71766946 Evinrude introduced the E-Tech system, an improvement to the Ficht fuel injection, in 2003, based on U.S. Patent 6,398,511. In 2004, Evinrude received the EPA Clean Air Excellence Award for their outboards utilizing the E-Tech system. "2004 Clean Air Excellence Awards Recipients" , EPA website, 2004 Yamaha also has a high-pressure direct injection system for two-stroke outboards. It differs from the Ficht/E-Tech and Orbital direct injection systems because it uses a separate, belt driven, high pressure, mechanical fuel pump to generate the pressure necessary for injection in a closed chamber. This is similar to most current 4-stroke automotive designs. EnviroFit, a non-profit corporation sponsored by Colorado State University , has developed direct injection retrofit kits for Two-stroke Motorcycles in a project to reduce Air Pollution in Southeast Asia , using technology developed by Orbital Corporation of Australia . Envirofit works to retrofit the Philippines The World Health Organization says air pollution in Southeast Asia and the Pacific causes 537,000 premature deaths each year. The 100-million two-stroke taxis and motorcycles in that part of the world are a major cause.http://www.ernasia.org/index.php?option=com_content&task=view&id=313&Itemid=75 http://www.worldwatch.org/node/5267 REFERENCES EXTERNAL LINKS
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