Fuel Pressure Fuel Rail
Amongst other things, the pressure in the fuel rail is dependent on:
- The capacity and speed of the high pressure pump, i.e. how much fuel the high pressure pump supplies based on the request of the engine control module (ECM)
- The time that the control valve, fuel flow, is closed, which is controlled by the engine control module (ECM) based on the desired fuel pressure
- Injected amount of fuel
- Exhaust valves
- Spark plugs
- Injector
- Inlet valves
The nozzle on each of the fuel injectors has six outlet openings. The type of injection is designated as multi-port injection.
Each one of the six tapered fuel injection jets is individually adapted to the combustion chamber's conditions.
The advantage of multi-port injection compared to single-port injection is that the jet pattern can be set exactly both with regards to angle and shape.
The fuel injector's central placement means that the fuel can be distributed uniformly and that the mixture can be dispersed optimally in the combustion chamber. It has a positive impact on:
- exhaust emissions,
- fuel consumption,
- tendency to knock, and
- oil dilution through the fuel.
With direct fuel injection, the gasoline is injected directly into the combustion chamber. Direct injection on a gasoline engine with turbo gives a fuel-efficient engine with high low rpm torque and high top power. One of the advantages of the direct-injected engine is that the gas mixture in the combustion chamber can be kept relatively cold. This gives higher resistance to knock, which can be used to give the engine a higher compression ratio and/or an higher ignition.
The lower temperature results from cooling/vaporization in a direct-injected engine takes place in the combustion chamber. Vaporization of the fuel reduced the temperature and increases filling. Taking the vaporization heat from the cylinder gas instead of from the inlet manifold's walls means that direct-injected engines can use a high compression ratio.
To reduce the temperature even more, air is directed through the cylinders during the camshafts' overlap (inlet and exhaust valves open at the same time) with positive pressure difference since the inlet pressure is higher than the exhaust pressure. In addition to cooling more, remaining gases from the previous combustion are also removed which otherwise would contribute to knock. To maximize cooling and to ensure correct vorticity, the geometry of the combustion chamber is optimized. The piston top, for example, is designed to minimise fuel wetting during homogeneous operation (injection early during inlet stroke) and direct the fuel mixture against the spark plug for any stratified operation.