Direct fuel injection in gasoline engines is not a new idea. In years 30. it began to be used in military aviation to ensure continuity of power supply in various positions of the aircraft and at different values of ambient pressure and to eliminate the carburetor, which was covered with ice at high altitudes. Fuel economy and exhaust gas composition did not matter at that time. After the Second World War, the idea was picked up by automotive designers. In two-stroke engines, High performance DKW has thus been able to reduce the losses in flushing the cylinder. In the early years 50. Bosch's direct injection systems were also fitted to the two-stroke engines, small cars Gutbrod 600 i Goliath. In the four-stroke engine, such a solution was introduced in 1954 r. in Mercedes 300 SL, for the best possible performance. They were also installed on the Formula W196 racing models 1. Attempts were also made to implement it into Wankel engines. All these systems were mechanically controlled. Only the development of electronics made it possible to significantly improve them in the direction of lowering fuel consumption and limiting the emission of harmful components in the exhaust gas., while maintaining the dynamics and flexibility of the engines.
In practical implementations of direct fuel injection in gasoline engines lean combustion is used (with excess air lambda coefficient above unity). After Toyota (Lean Burn), Mitsubishi (GDI) and Renault (HERE), Volkswagen engineers chose this path, cooperating with Bosch specialists.
The Lupo FSI adopts two methods of direct fuel injection into the cylinder. First – layered – is used, when the engine is running at part load (slow driving in low gears, driving at a constant moderate speed, riding on flat ground). Second – with complete mixing of fuel and air – is used, when the engine is running under a heavy load (acceleration, riding uphill, driving at speeds in excess of 3/4 maximum speed).