AN IMPACT OF USING A DUAL-INJECTION SYSTEM ON A COMBUSTION ENGINE'S WORKING

The paper analyses the impact of using a dual- injection system on the eng ine's working parameters. The analysis is based on the results o f the test stand research on a four-stroke four-cylinder, spark-ignition engine. Dual-injection system combines the multipoint injection with additional injection directly into the combustion chamber. It is used to increase the performance of an engine without affecting the fuel consumption or the low toxicity of exhaust gas. For the purposes of this research an en gine from Toyota Yaris wa s fitted with th e direct injection by insta lling high pressure injectors on th e cylinder head. This engine is factory-equipped with MPI. Based on the tests performed four controlling characteristics of the torque and brake specific fuel consumption were pre pared. The con trolling value was the proportion of the fuel injected into the inlet channel to the fuel injected directly into the combustion chamber. The same rela tionships were also described in relation to temperature of the exhaust gas and the fraction in volume in the exhaust gas of ingredients such as carbon monoxide, carbon d ioxide, unburned hydrocarbons and nitric oxide. Points of measurement were decided upon based on the existing literature on the subject. The analysis of the test results shows a possibility of a 2-4 % decrease in the brake specific fuel consumption for the dual- injection engine in the low and middle RPM range and for the partial loads. The dual-injection engine also shows a decrease in the nitric oxide's fraction in the exhaust gas and a lower temperature of the exhaust gas. There was a small increase in the carbon monoxide and hydrocarbons