## 4 Discussion
Therefore, the demand for increased torque (caused by appearing elements to be chipped) could not be considered by the injection system. This reduces the rotational speed and the ability to achieve the maximum torque value. The system was designed in such a way that during idle operation it rotates at speeds greater than that required to achieve maximum torque. The appearance of the load results in a decrease in the rotational speed, and, in turn, it reaches a value guaranteeing the maximum torque to be obtained. This is in accordance with the actual operating characteristics of the internal combustion engine. The combustion engine with the fuel injection system (A) used in the first stage tests ensured that the fuel-air mixture was maintained at a similar level during chipping. It was done by reducing the rotational speed (and the number of cycles) which led to lower fuel consumption. As a result of applying an injection system (B), the fuel consumption during idle work with low rotational speed decreased at about 38%. During idle work at high speed, the fuel consumption increased by 9%. In the case of chipping objects that caused a significant load of the drive, the modification allowed the lowering of fuel consumption by 61% (Figure 3). The second stage fuel consumption test results allowed for a comparison of the fuel consumption in periodically-variable exploitation conditions (4) with different fuel supply systems (Figure 4). To compare systems in constant conditions, we supplied the branches in such a way that allowed us to keep a constant ratio between chipping and idle work. If the operating conditions were close to reality, the carburetor system with the classic control system showed a significantly higher (by 56-70%) fuel consumption than the injection system. Another important factor affecting fuel consumption was the method of controlling the injection system. An adaptation of the system to operating conditions ensured a reduction of fuel consumption compared to classic control (with carburetor-A) by about:  
* 24% with a chipping/idle work ratio of 78% to 22%,
* 50% with a chipping/idle work ratio of 71% to 29%,
* 60% with a chipping/idle work ratio of 65% to 35%. Fuel consumption in the adaptive system was largely dependent on the ratio between chipping and idle work times. This value decreased with the increase of idle work during machine operation time in processing operations. The above comparison of drive control systems and concepts shows that the average fuel consumption per hour (apart from the injection time) is affected by the rotational speed, on which the number of cycles of the internal combustion engine depends. The introduction of a system with the possibility of adaptation (in terms of mechanical power) to operating conditions will reduce fuel consumption. A similar method of reducing emissions from the internal combustion engine was used in motor vehicles by introducing the start-stop system. It is estimated that using systems of this kind reduces fuel consumption and carbon dioxide emissions by 5-10%, and in hybrid vehicles by 10-25% [47; 48]. [PERSON] et al. [34] showed that the start-stop system is used for 20% of the time when the vehicle is operating in the urban environment. For chipping machines, the frequency of changes in operating states, and especially the length of idle work time is too short to enable turning the engine off. According to the authors, the rotational speed decreasing system is beneficial. In addition, system utilization time can be assumed to be 20% or more over the entire operation cycle time, according to the test results concerning real conditions for mobile chipping machines. The quantitative reduction of exhaust gas emissions results from the decrease in fuel consumption, but the quality of exhaust gases is also important. The adaptive system is characterized by the extended work time in a transient state.