Control problems in a turbocharged spark-ignition engine

The paper presents the problems of adapting of the charge system to the standard four stroke spark ignition engine Toyota Yaris 1300 cm3 with compression ratio 10.5. The main problem in charged spark ignition engine is control of air-fuel ratio near stoichiometric values at different boost pressure in order to obtain higher torque at the same level of specific fuel consumption and exhaust gas emission. Charging of such engine is connected with the problem of knock in the medium and high values of load at low engine speeds. Higher boost pressure leads to abnormal combustion process and to knocking. The paper describes the boost pressure control algorithm which enables to prevent the knock, so the engine can work near the knock boundary. The article includes a description of the engine, the method of charging and test bench, which was built to verify the proposed control algorithm for boost pressure. The publication contains the results of different tests conducted on the supercharged engine stand by the proposed algorithm and measured parameters were torque, fuel consumption and volumetric concentration of the main exhaust gas components. Applying of turbocharger in SI engines leads to knocking. The controlling of combustion process in SI engine is realized on the adjustment of WG or VTG to decrease or increase the rotational speed of turbocharger. Such control causes the engine work near boundary of knocking.