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Internal combustion engines of vehicles which are equipped with classic drivetrains are mostly operating in variable load conditions. This fact especially refers to city driving, where the vehicle speeds are lower than in highway driving, but the accelerations are more frequent and intensive. The efficiency of the engine’s work is among others a load- and crankshaft rotation speed dependent parameter. Generally in low load conditions the efficiency of the engine is low, and in high load the efficiency is high. The authors conducted a series of road tests, searching for ranges of engine power most commonly used in urban traffic, adopting economical, dynamic and balanced driving strategies. In all strategies the passenger vehicle engine was most frequently operating in low power (and low efficiency) conditions. One of the ways to improve the efficiency of an IC engine is to raise its compression ratio (CR).

The vibrations of the sprung mass of a passenger car, traveling along a road surface, are random. They also form its main source but there are besides other factors to consider. The resulting force ratio is overlapped by other phenomena occurring at the interface of the pneumatic tire with the road surface, such as non-uniformity of tires, shape deformations and imbalances. The resulting additional inertia force acts on the kinematic force that was previously induced on the car body. The vibrations of the sprung mass of the car body at the time can be considered as a potential source of diagnostic information, but getting insight their direct identification is difficult. Moreover, the basic identification is complicated because of the forces induced due to the random interference from road roughness. In such a case, the ratio defined as SNR assumes negative values.

This paper presents the results of research, whose aim was to design and build a prototype device for the estimation of traction parameters of a car, including power output from engine. The estimation of the power of the powertrain system follows on the basis of measurements of the car's longitudinal acceleration in a special road test in actual driving conditions. The measurement of the longitudinal acceleration brings a number of problems which were solved due to the application of the new measurement method. The factors affecting deficiency of the precision of measurements and the methods applicable for its reduction were developed. As a result, it was possible to obtain a measurement method with reduced uncertainty and increased repeatability in terms of results. In addition, an interpretation of the results of the test is presented in reference to the power of the powertrain and engine.

In this paper the application of spectral and wavelet analyses in power train system diagnostics were shown. The main goal of investigations was a comparison of changes of selected values measured by accelerometer installed in the car body during particularly designed road test. The investigation object was passenger car and the experiments were performed with use of special measuring device. The logged data were analyzed using amplitude spectrum and short time Fourier transform (STFT) algorithms implemented in Scilab software. The transformed data were compared with continuous wavelet transforms (CWT), which were obtained with use of Morlet's and Mexican hat analyzing wavelets. The advantages and disadvantages this transforms were discussed. As main effect of investigations it can be concluded, that the STFT and CWT algorithms can provide more diagnostics information then the other transforms.

The paper presents the properties of a prototype universal portable device for the determination of parameters of road vehicle driveability. The objective of this device is to enable the determination of driveability parameters in road vehicles. In this solution driveability parameters are determined only on the basis of acquired longitudinal acceleration during particularly designed road tests. The acceleration is measured with the use of accelerometer installed in the car body. During execution of the project numerous problems associated with the method of vehicle acceleration have been solved. Sources of errors in measurement method were determined. Methods and algorithms of road test time disturbances reduction were indicated. As a result accuracy of driveability parameter increased beside the repeatability of test results. The interpretation of the determined parameters is discussed in relation of road test course.