This mode significantly affects the noise of the engine and the amount of emissions of harmful substances into the surrounding space. This mode is characterized by a relatively low 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 interval is determined by the conditions of fuel atomization. Exceeding the upper limit leads to an increase in the noise of the engine and an increase in the amount of harmful emissions (particulate matter).
Pre-injection is implemented in almost the entire range of engine operating modes up to a speed of 3500 rpm and a fuel pressure in the TKVD of 1200 bar (120 MPa).
The pre-injection mode is disabled under the following circumstances.
- The engine speed is too high.
- Estimated fuel supply is too low for pilot injection.
- Estimated fuel supply for main injection is too low.
- Insufficient amount of fuel in the TKVD.
- Engine stopped.
The amount of fuel allocated to the pilot injection is part of the total amount of fuel calculated for the entire cycle.