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Direct Fuel Injection
The direct fuel injection (DFI) used in the new 911 flat-six engines is based on homogeneous direct injection. In this process, electro-mechanically controlled fuel injectors inject the fuel directly into the combustion chamber at a pressure of approx. 580 psi to 1740 psi (40 to 120 bar) and with millisecond accuracy as required by the respective driving state. The mixture of air and fuel is distributed as evenly as possible in the combustion chamber, thereby allowing optimal combustion.
The spray cone angle and injection-jet orientation have been optimized to achieve optimum homogenization in the entire operating range. Within the injector, the fuel jet is twisted (rotated around the longitudinal axis). This rotation forms a conical cloud of fuel. The fine atomization produced in this way allows faster evaporation of the fuel.
The heat energy required to evaporate the fuel is absorbed from the combustion air, thereby cooling the air. This reduces the cylinder charge volume and additional air is drawn in through the open intake valve, which in turn improves cylinder charging.
Lowering the temperature reduces susceptibility to knocking and additionally allows the compression ratio to be increased. The higher compression ratio in turn increases the engine efficiency. This reduces fuel consumption, particularly in the partial-load range.