In the early stages of the automobile, there was only one priority: High driving performance. Fuel consumption was, initially, a minor matter. Therefore the first attempts to reduce the consumption of petrol emerged in the 1950s. First, the car model Gutbrod Superior 700 E came into the picture, which received a direct petrol injector built into the two-stroke engine by former aircraft engine constructor Hans Scherenberg. A short time later another car, the Goliath 700 GP, was also driving the streets with this technology.What does that mean exactly?The difference between the injector types built into those cars is evident in the terms themselves: As opposed to the conventional injection for Otto engines, where the injection valve is located in the inlet manifold in front of the intake valve, direct injection involves injection directly into the cylinder.
And, as is so often the case in life, the direct route is the best: This technology, developed for aircraft construction, resulted in a saving of 30 percent.

The first “baby steps" with regard to this technology, however, occurred already earlier. As a pioneer, BMW conducted the first trials with the BMW VI, a four-stroke, twelve-cylinder engine. The technology worked so well that in the 1930s, Mercedes-Benz implemented it in supercharged four-stroke aircraft engines. Almost two decades later, in 1954, Mercedes-Benz also delivered for cars: The high performance engine of the 300 SL was also temporarily equipped with petrol direct injection. Three years later however, in 1957, the change was made back to inlet manifold injection, because the direct injection procedure caused problems through the thinning of oil. The revival of this technology however came ten years later when, in 1967, Volkswagen also experimented with direct injection technology: The Volkswagen 1600 TL for the first time received electronically controlled petrol injection. Since then, engineers have been ardently exploring the combustion process in the motor, in order to improve efficiency internally, eg. with modifications to the piston crown and pistons.
But as usual there are different ways to reach the goal: An alternative fuel saving concept was brought to the public in 1964, when the Auto Union introduced the Audi 72 to the market, with a medium pressure motor. The piston crown in this motor contained a spherical combustion chamber, which lead to improved combustion. Many modifications were to follow, including, among others, the electronic throttle control from BMW at the end of the 1990s.
Another steppingstone in the right direction was reached as early as 1947, when the American Ralph Miller received a patent for his overlapping valve timing design. The new thing about this was that the inlet valve remained open at the beginning of the compression process. Thus, a small amount of air-fuel mixture was expelled, which would then be immediately available for the following intake stroke without delay. Honda, Toyota and BMW developed this concept further in introducing intelligent valve control to their motors, which provided for different valve opening times for different driving conditions. In the 1980s, Cadillac equipped its eight-cylinder engines with a cylinder cut-off. Four, six or eight cylinders were in operation at any one time, depending on power requirements. This also led to a saving in fuel.A further development was the lean burn motor, first introduced by Toyota in 1991. Here, the fuel-air mixture was kept extremely lean (that is, with an excess air ratio of 1:21), which led to reductions in consumption, but also entailed disadvantages in starting. The lean burn mixture could only be realised in certain rpm ranges, and the unsatisfactory results lead to the abandonment of the lean burn principle.
In 1997 Mitsubishi went back to the roots of direct fuel injection by presenting the Charisma GDi (Gasoline Direct Injection), the first mass-produced vehicle with petrol direct injection. Volkswagen followed with the FSI motor in 2000. Meanwhile, more and more manufacturers are using this technology – especially in connection with turbocharging and/or supercharging, with which the fundamental torque weakness of petrol direct injection can be remedied. The real success of direct injection in automobile construction, however, began with the advanced development of the diesel engine. The Volkswagen Golf Diesel revolutionised the market in 1976 with the first fast-running diesel engine with a 1.5 litre motor (37 kW/50 hp). This engine accelerated the compact vehicle to 140 km/h, at what was at the time an amazing consumption of 6.5 l/100 km – with a little bit of restraint, less than five litres was also possible. A further advance in development was brought about by the introduction of turbo diesel direct injection, which has presented at the IAA in 1999 by Volkswagen subsidiary Audi. Here, also, the fuel is injected directly into the cylinder, which means that the prechamber or swirl chamber otherwise customary in diesel motors can be foregone. The advantage of direct injection is its efficiency, however in the early stages of development the price of this was loud combustion noise. The motor of the first Audi 100 TDI series had five cylinders, supplied 88 kW (120 hp) and could be driven with consumption figures between six and seven litres. Previously, Fiat had already introduced common rail direct injection, developed in cooperation with Bosch, in the Croma. The common rail motors are now considered to be gentle bruisers.

Currently, engineers in the automobile industry are working on the combination of diesel and Otto engines. Accordingly, with the “Diesotto” Daimler Benz presents a 1.8 litre petrol engine which is compressed to a similar level to a diesel, and for which the premium fuel is ignited automatically in some rpm ranges, as in a diesel. Synthetic fuels and complex emission controls, eg. with the injection of urea by the Mercedes “Bluetec” models, should however make the diesel a sustainable option for the future.One current trend of motor development is downsizing – a reduction in engine size, which generally leads to a reduction in consumption. The loss of power is compensated for by the supercharging or turbocharging. As such, with the 1.4 TSI Volkswagen introduced a 1.4 litre petrol direct injection engine, which is inspired with a supercharger and a turbocharger. The result is a full 125 kW (170 hp), which results in on average 7.3 litres of premium fuel (174g CO2 per kilometre) for the Golf. With this, Volkswagen currently represents the spearhead of the new technology.Nowadays modern petrol direct injection engines use piezo technology. For diesel engines, direct injection with fast piezo injectors has led to noticeable fuel savings. In August, 2006, this technology was also used in an Otto engine for the first time, that of the Mercedes-Benz CLS 350 CGI. The advantage of piezo injectors: They inject the fuel into the combustion chamber so finely that it can be ignited immediately, and without mixing with air. The petrol can thus be used more efficiently. At the same time, constructors from Bosch, the specialists for injector pumps, are working on the development of petrol direct injection with magnetically controlled injector valves. The second generation of this technology also comes onto the market in 2007, and will premiere in a turbocharged 1.6 litre Otto engine developed cooperatively by BMW and PSA for the Mini Cooper S, among others.Automobile engineers see further potential savings in refining aerodynamics, and in the implementation of supporting units of a vehicle such as water pumps, hydraulic pumps, air-conditioner compressors and so forth, according to requirements. However, the selection of the “correct tyres optimised for minimum road resistance”, auto start/stop function and brake energy regeneration system also help to achieve significant savings. BMW is the most dedicated in this regard, and presents an entire bundle of these measures in its new EfficientDynamics models
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