## 3 Development and Production of Vehicle
### Modification of the Engine
It was necessary to design the throttle so that it could be easily and quickly dismantled for inspection purposes during the race. At the same time, it was necessary to think about electronic opening/closing of the damper in order to significantly facilitate the control of the engine for the pilot (Figure 16). During the preparations for the Shell-Eco Marathon 2019 race, the pistons were gradually changed and power and consumption were measured on the engine brake. For each piston, it was necessary to set the engine control program so as to achieve the lowest possible fuel consumption with the highest possible torque. The measured values were compared and put together the engine with the most efficient parameters for the competition. In the beginning, the original, serial engine was measured. It was already clear during the preparation of the technical documentation for the production of pistons that if the effort is to achieve low consumption, it will be necessary to get the engine characteristics completely elsewhere. Due to the fact that the original engine was not designed for low consumption, it was necessary to keep the operating speed of the engine as low as possible. To do this, it was necessary to design the engine so that it had the lowest idling speed. For comparison, the original engine had a working speed of 7000 RPM and an idle level of 3500 RPM. The proposed modifications to the engine got a working speed of 3500 RPM and idled up to the level of 1500 RPM, which was extremely demanding. The fly wheel also had to be modified with regard to electronic starting. All this while maintaining low weight  
Figure 14: Piston models in Solidworks. Figure 15: Manufactured pistons with different numbers of grooves for piston rings and different compression ratios. and easy assembly/disassembly from the vehicle. The aim was to achieve the lowest possible engine consumption at the highest torque. The monitored values, which were measured and evaluated, were based on the torque and consumption at a given speed. Speed was measured from idle to maximum. The value of torque and consumption was measured in differences of 250 RPM, which gave a large range of measured quantities and helped in further design of gear ratios in the transmission. Engine consumption was evaluated in grams per kWh. The engine was run under load at the selected speed for 1 min and then the consumption was measured. The following graphs show the engine torques and consumption (Figures 17-24). The final evaluation of the achieved values is summarized in the final table (Table 3). Figure 16: Mounted throttle system with electronic opening control and injector. Figure 17: Engine torque characteristics for serial piston. Figure 19: Engine torque characteristics for piston no. 1. Figure 18: Fuel consumption characteristics for serial piston. Figure 11:0 Engine torque characteristics for piston no. 2. Figure 11:1 Fuel consumption characteristics for piston no. 1. Figure 11:2 Engine torque characteristics for piston no. 3. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Height h [mm]** & **Compression Ratio** & \
\begin{tabular}{c} **Maximum** \\ **Torque/Revolutions** \\ \end{tabular} &
\begin{tabular}{c} **Lowest** \\ **Consumption/Speed** \\ \end{tabular} \\ \hline Original piston & 13.6 & 8.0:1 & 1.6 Nm/5500 RPM & 980 g/7000 RPM \\ \hline piston1 & 14.1 & 10.0:1 & 1.79 Nm/4000 RPM & 450 g/4250 RPM \\ \hline piston2 & 14.6 & 12.0:1 & 1.5 Nm/4000 RPM & 520 g/4000 RPM \\ \hline piston3 & 15.1 & 14.0:1 & 2.12 Nm/3500 RPM & 275 g/3500 RPM \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparison of engine characteristics using different pistons. Figure 22: Fuel consumption characteristics for piston no. 2. Based on the data, piston no. 3 (blue line) and at the same time the characteristics of the torque engines were compared with the piston of the original series engine (red line) and with the optimum, i.e., with the piston 3 (Figure 25). Figure 24: Fuel consumption characteristics for piston no. 3.