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Abstract

The paper provides an analysis of a VNT-type turbocharger implementation influence on operating parameters of the spark-ignition engine with additional expansion of exhaust gases. Previously, the research of the engine was performed with a charging system composed of a turbocharger with a simple waste-gate valve. The research was done mainly in order to improve the engine's performance for lower rotational speed range. The second reason of the described modification was to obtain lower fuel consumption. The four series of tests with boost pressure rising gradually from 0 to 0.8 bar were conducted for rotational speed of range 2000-3200 rpm. The described analysis of the obtained results showed that application of the VNT-type turbocharger caused significantly improved performances of the engine, especially in a lower rotational speed region. Also, decrease in the brake specific fuel consumption of the spark ignition engine with additional expansion of exhaust gases has been achieved for the rotational speed of value 2400 rpm.