Search Results

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.