Researched regimes of engine operation without load: 1 – test of the original engine; 2 – test with disconnection of four cylinders by stopping the fuel supply; 3 – test with the disconnection of four cylinders by simultaneously stopping the fuel supply and the absence of pumping losses of the cylinder-piston group (CPG) of the disconnected cylinders. It was established that when the crankshaft rotation frequency increases from 1400 min-1 to 2550 min-1 when the fuel supply to half of the cylinders is turned off, the fuel economy changes from 0 to 0.53 kg/h. When the fuel is turned off and there are no CPG pumping losses, the fuel economy changes from 1.2 kg/h to 3.88 kg/h. Recommendations have been developed that allow to increase the efficiency of wheeled vehicles by 11-26% by disconnecting a part of the cylinders.

The conducted systematic analysis of maintainability indicators allows establishing their connection with other reliability properties and classifying these indicators according to technical and economic criteria. On this basis, the technological component of maintenance and repair, which ensures the provision of spare parts, tools and means of technical condition control, was selected and investigated. Set of indicators that allow to evaluate and standardize the maintainability of means of transport most fully and in accordance with modern requirements is proposed.The dependence was obtained for determining the required number of tools in a set of spare parts, tools and accessories (STA), which takes into account the reliable characteristics of the machine and the characteristics of the process of restoring its operability under real operating conditions.The approach to calculations of rational sets of tool equipment for vehicle machinery is proposed on the example of the chassis of the domestic wheeled tractor KhTZ-17221, the corresponding calculations are performed. The conducted analysis shows that with the existing service system and the level of reliability of the KhTZ-17221 tractors in real operation conditions to ensure the readiness factor within 0.85-0.95, the presence of tools in the equipment kit has a significant impact.The analysis of the obtained dependence shows that in order to quickly eliminate the consequences of the failures of the KhTZ-17221 tractors, it is necessary to have a complete set of tools in the set of STA, provided for in the operating instructions. Otherwise, the operative time for eliminating failures increases, which leads to unjustified downtime of equipment and increased costs for consumers, especially during periods of agricultural work. When increasing the number of tools in the kit of STA to the level regulated by the factory documentation, while maintaining all other parameters, it is possible to increase the readiness factor in real operation from 0.84 to 0.92. That is, the presence of tools significantly increases the efficiency of vehicles using in real operation conditions.The obtained results can be used to improve maintainability indicators