## 4 Discussion  
1. Speed characteristics at a full load: * Obtaining higher values of torque and effective power (entire range) for the maximum HVO dose at the maximum volumetric dose of HVO fuel (Figure 4). Max 4% increase. * Achieving lower specific and hourly fuel consumption (whole speed range) for DF--max 2% (Figure 5).
2. The analysis of the results of the instantaneous pressure and temperature in the combustion chamber as a function of the crankshaft rotation angle shows the following for HVO fuel: * Earlier start of the combustion process by 2 degrees CAD (Figure 6) and, consequently, an increase in the maximum temperature in the combustion chamber by approximately 30 K and in the maximum pressure by 0.3 MPa for the maximum load and rotational speed of 1300 rpm (Figures 7 and 8). At lower loads, the differences are smaller for both fuels, and at an engine load of 25%, no difference was observed. * Earlier start of the combustion process, resulting in an increase in the maximum temperature in the combustion chamber by approximately 20 K and in the maximum pressure by 0.2 MPa for the maximum load and rotational speed of 1600 rpm (Figures 9 and 10). At lower loads, the differences are smaller for both fuels, and at an engine load of 25%, no difference was observed. * Earlier start of the combustion process, resulting in an increase in the maximum temperature in the combustion chamber by approximately 17 K and in the maximum pressure by 0.16 MPa for the maximum load and rotational speed of 1900 rpm (Figures 11 and 12). At lower loads, the differences are smaller for both fuels, and at an engine load of 25%, no difference was observed. * Earlier start of the combustion process, resulting in an increase in the maximum temperature in the combustion chamber by approximately 17 K and in the maximum pressure by 0.16 MPa for the maximum load and rotational speed of 1900 rpm (Figures 11 and 12). At lower loads, the differences are smaller for both fuels, and at an engine load of 25%, no difference was observed.
3. Emissions of harmful substances: The speed characteristics (Figure 13) show that NOx concentrations are higher for HVO fuel (by a maximum of 18%), and particulate matter is 50% lower than for DF. The load characteristics for 1300 rpm (Figure 14) show that NOx concentrations are higher for HVO fuel, but only at the maximum load. As the load decreases, the trend reverses and HVO fuel shows a maximum of 7% lower NOx concentration than DF. In the case of HVO fuel, PM emissions in the entire range of tested load characteristics show lower emissions by up to 75% (at a low engine load). On the load characteristics for 1600 rpm (Figure 15), NOx concentrations are higher for HVO fuel, but only at the maximum load. As the load decreases, the trend reverses and HVO shows a maximum of 17% lower NOx concentration than DF. In the case of HVO fuel, PM emissions in the entire tested load range are lower by up to 58% (at a low engine load). On the load curve at 1900 rpm (Figure 16), NOx concentrations are about 17% lower for HVO, but only at the maximum load. As the load decreases, both fuels show similar emissions (maximum 4% difference) For HVO, particulate matter in the entire tested range is characterized by lower emissions by up to 56% (at a low engine load).
4. The specific NOx emissions determined in the ESC test for the Perkins 854E-E34 TA engine are 2.3% lower for HVO. Specific PM emissions are 43% lower for HVO compared to DF.