TURBOCHARGING OF NATURALLY ASPIRATED SPARK IGNITION ENGINE WITHOUT MODIFICATION OF A COMPRESSION RATIO

The objective of research was to determine total efficiency and performance of turbocharged small displacement SI engine without modifying engine control unit. The engine used during the investigation was Toyota yaris 1296 cm3 displacement SI engine with modified intake manifold. There was variable and fixed geometry turbocharger mounted in the exhaust system. Inlet air pressure was controlled by introducing a waste gate valve. Specific values of maximum boost pressure were obtained thanks to implementation of different valve springs. The outcome of investigation shows that there is a possibility of introducing turbocharger without modification of intake system and engine’s control unit. Implementation of turbocharger with variable turbine geometry and waste gate valve controlling maximum boost pressure permits significant improvement in torque characteristic without exceeding permissible harmful exhaust gases emissions. Change of waste gate valve spring’s characteristic allowed reaching higher torque and making its value constant in wide range of engine’s rotational speed. Change of waste gate characteristic permitted to achieve advantageous torque characteristic, maximum torque rise and its constant value in wide range of engine’s speed.