Indirect injection

Adding indirect injection keeps fuel spraying on the intake valves, reducing or eliminating the carbon accumulation on intake valves and in low load conditions, indirect injection allows for better fuel-air mixing.

This system is mainly used in higher cost models due to the added expense and complexity.

Port injection refers to the spraying of the fuel onto the back of the intake valve, which speeds its evaporation.

The prechamber is carefully designed to ensure adequate mixing of the atomized fuel with the compression-heated air.

[3] The addition of a prechamber increases heat loss to the cooling system and thereby lowers engine efficiency.

Direct injection, by contrast, uses slow-moving air and fast-moving fuel; both the design and manufacture of the injectors is more difficult.

[5] After combustion, the products return through the same throat to the main cylinder at much higher velocity, so more heat is lost to the walls of the passage.

At its top dead centre (TDC) the majority of the charge mass is contained in the cavity and air cell.

[citation needed] When the injector fires, the jet of fuel enters the air cell and ignites.