The efficiency of a car is considered through the amount of energy loss spent on transmission from the engine to the driving wheels of the car. Analytical and experimental methods for assessing mechanical losses are analyzed. The advantages and disadvantages of road and bench tests of a car in free run modes are indicated. A description of the diagnostic equipment - a stand with running drums, used to simulate the movement of a car in laboratory conditions is given. The components of the necessary measuring equipment for recording the speed and torque on the wheels of a car are considered. The list of primary measuring sensors and main transducers is indicated, which transmit information to the computer. The results of the car run-out on the stand are given: the change in the instantaneous speed from time to time. The primary assessment of the regression model is made and the values of the coefficients are obtained by the method of least squares of deviations of the vehicle speed. A mathematical model for the subsequent processing of experimental data has been developed. The purpose of mathematical modeling is to separate mechanical losses by power units separately for the engine, transmission and car wheels. An assessment was made of the amount of energy losses in the stand itself with running drums. The characteristic of the stand has been obtained, which must be taken into account in the measurement procedure. The results of experimental studies for the GAZ-31029 car are presented. The results of the influence of the technical condition of transmission units and vehicle wheels on the value of the power of mechanical losses are presented. Car tire pressure studies have been conducted. The graphical dependences of the power of mechanical losses depending on the speed of the car are obtained. Recommendations have been developed for diagnosing the general condition of the vehicle by the amount of mechanical losses at the stand with running drums. The ways of further improvement of the method are given. The main conclusions based on the research results are formulated.

Fuel efficiency is one of the indicators for evaluating the efficiency of rolling stock. The article discusses the main reasons that determine the need to assess the fuel efficiency of road vehicles during their operation. An analysis of recommendations for the accuracy of measuring vehicle parameters in regulatory documents was given. The goal of the work was formulated, which is to develop measures to improve the accuracy of measurements during bench tests of cars. The main features of measuring fuel consumption on a simulation stand with running drums were considered. Formulas for calculating fuel travel on the road and on the stand with running drums were presented. A criterion for the similarity of road and bench tests for the fuel efficiency of a car was determined. The factors that influence the measurement of fuel consumption were considered. The general measuring scheme of the simulation bench was drawn up. The components of the load-speed modes for the stand operation were analyzed. A metrological assessment was made of the equipment used to measure the torque and rotation speed of the drive shaft of the running drums. A diagram of the calibration process of a strain gauge beam was given, which is used to measure the torque on the running drums of the stand and the wheels of a car. An assessment was made of the regularity of the change in the output channel of the measuring signal from the torque. The characteristic of the relative error was obtained for two ranges of load measurements. The influence of the frequency and number of successive measurements on the convergence of the accuracy of determining the fuel consumption, speed and load of the vehicle during bench tests was established. The optimal measurement time was obtained with an acceptable accuracy. The general dependence of the total error in measuring fuel consumption on a stand with running drums was obtained, taking into account the accuracy of measuring, processing and sampling the signal. The influence of the sampling frequency of the analog-to-digital conversion on the measurement accuracy was assessed. Conclusions and recommendations were developed, which indicated the main avenues for further research.

The article proposes a method for assessing the change in the braking properties of passenger cars during operation following a change in the main characteristic of the brake system - the coefficient of distribution of braking forces between the axles of vehicles, both equipped and not equipped with tracking systems for the braking process by installing brake force regulators in the brake circuits, working according to different laws of changing the drive pressure. The aim of the work is a comparative assessment of the braking efficiency of passenger cars using the example of Lanos cars, the braking systems of which are equipped with various devices for changing the coefficient of distribution of braking forces between the axles, under changing operating conditions. It is known that braking efficiency is an indicator characterizing the braking properties and the ability of a car to maintain a given law of motion during braking, which is determined both by the nature of the adhesion properties of the wheels to the road and the capabilities of the braking system itself to implement these properties. Since the operating conditions of passenger cars significantly affect the braking properties, in order to ensure the required braking efficiency, it is necessary to take into account the change in the primary distribution coefficient of the braking forces generated by the braking mechanisms and the change in their implementation during the operation period. In order to assess the change in the braking properties in the general case of the operation of a passenger car, the dependence of the actual coefficient of distribution of braking forces between the axles on the braking coefficient was proposed. Moreover, the value of the coefficient of distribution of braking forces between the axles depends both on the type of laws of regulation of braking forces and on the residual values of the parameters of braking systems that determine these laws. These dependences on the parameters of the braking systems and the parameters of the passenger car in operation are a function of the goal for determining the residual output characteristics of its braking system.

The scheme of energy transmission from the engine to the wheels of the car is considered. It is indicated that the dynamics of the vehicle when driving in low gears is significantly influenced by the value of the moment of inertia of equivalent masses. For a passenger car, when driving in first gear, the equivalent weight can increase up to 28%. In the literature, inertial masses are determined approximately. The article proposes a simple technique for assessing the moments of inertia of the main parts (wheels, transmission, engine) without disassembling the car. The essence of the method is to measure the deceleration during free run of the car with the vehicle's wheels hanging, and then without the wheels. A system of equations for the power balance of the vehicle run-out in 3rd and 4th gears of the gearbox with open clutch is compiled. When drawing up the equation, it was assumed that with the same engine speed and the same throttle opening, the engine torque would be the same. Formulas are obtained for calculating the moment of inertia of the wheels and the variable part of the transmission, according to which the inertial mass of the engine is calculated without the need to remove it from the machine. The article describes the experimental research methodology applied to the Hyundai i30 car with a working volume of 1.4 liters, manufactured in 2007. In the course of the experiment, the engine speed was measured through the OBD II connector, using the ELM 327 adapter and the ScanMaster-ELM program, the vehicle on-road speed using the Garmin eTrex 30 navigator, and the wheel revolutions were recorded on video. During the experiment, the condition of the tires Nokian Nordman SX 195/65 R15 91H was monitored, for which the residual depth of the tire tread pattern, pressure, moment of inertia were determined (by the bifilar suspension method). Based on the results of the experiment, the developed mathematical model was used to calculate the moment of inertia of the rotating parts of the Hyundai i30 in different gears. The result of the study allows you to establish the actual state of the rotating parts of the car, the knowledge of which increases the accuracy of determining the performance characteristics. The technique can be used to diagnose the conditions of transmission elements and car wheels. The technique does not require the use of complex stands and expensive devices.

Decision-making in solving the problems of auto technical examination of road accidents (road accidents) is carried out in conditions of incomplete information, ie in conditions of uncertainty, which may be stochastic or fuzzy in nature, and therefore is compositional. When forming expert opinions of auto technical examination of road accident the general uncertainty is formed due to uncertainty of the chosen structure of model of road accident, experimental data, error of measuring devices, adequacy of model of road accident, uncertainty of indications of witnesses and other proofs, competence and honesty of the expert. The calculation of vehicle parameters in motor vehicle expertise in the vast majority of cases is performed without estimating the error of the results, which does not meet the requirements of the Law of Ukraine "On Metrology and Metrological Activity" and determines the relevance of improving methods of solving road accident technical examination. The paper reveals the prospects of improving the existing methods of assessing the effectiveness of braking of wheeled vehicles, as the main way to prevent accidents in road transport, which is regulated by the current Traffic Rules. The basic theoretical dependences which form a basis of the improved technique of estimation of parameters of movement of cars at braking are presented. Analysis of the results of the calculations shows that by taking into account the design of the braking system, type and condition of tires used in assessing braking efficiency, the improved technique avoids the same solutions within one category of vehicles, and taking into account stochastic and fuzzy uncertainty narrows the range of possible solutions by 49.4 %. The probability of occurrence of type I errors is reduced by 1.75-18.5%, and type II errors - by 43.1-67.8%.