This mode has a significant impact on engine noise and the amount of harmful emissions into the surrounding space. This mode is characterized by a relatively small amount of injected fuel: from 0.5 mm³ to 1.5 mm³ per stroke at a fuel pressure of 200 bar (20 MPa). The lower limit of this range is determined by the fuel atomization conditions. Exceeding the upper limit leads to increased engine noise and an increase in the amount of harmful emissions (solid particles).
Pre-injection is implemented in almost the entire range of engine operating modes up to a rotation speed of 3500 rpm and a fuel pressure in the high-pressure fuel pump of 1200 bar (120 MPa).
The pre-injection mode is disabled under the following circumstances.
- The engine speed is too high.
- The calculated fuel supply is too low for pilot injection.
- The calculated fuel supply for the main injection is too low.
- Insufficient amount of fuel in the fuel injection system.
- The engine has stopped.
The amount of fuel allocated for pilot injection is part of the total amount of fuel calculated for the entire cycle.