Experimental Study On Cold Starting Performance Of Vehicle Gasoline Engine

With the improvement of people's awareness of environmental protection in China,the performance requirements for the economy and dynamics of automotive engine are also constantly increasing.The cold start of the car is an important condition for the optimal development of engine performance,which is gradually being taken seriously by major automotive R&D and manufacturing plants.In this paper the calibration method of cold start performance of automotive is studied.Firstly,the development history of automotive cold start match calibration and engine torque control strategy was introduced;then the latest engine management system(ME7 system),related critical sensors and engine technical parameters were introduced;finally the control strategy for the cold start phase of the engine was described,and the influence of starting enriched fuel injection coefficient and ignition advance angle on engine speed and excess air coefficient during engine start-up were made a special effort to study,and the start-up optimization calibration test of the whole vehicle was carried out based on the experimental results,so that the engine can obtain a better starting performance.(1)The engine torque control strategy,fuel injection quantity control strategy,air intake quantity control strategy and ignition control strategy were briefly described.(2)The fuel injection control model,the air intake control model,and the ignition control model were simulated by Simulink modeling.According to the rotation speed,the engine cold start was divided into three phases: synchronous,start,and warming up after starting,and the fuel injection calculation models were designed at different stages.The air intake volume calculation model and the calculation model of ignition advance angle were also designed.(3)By changing the rotate speed of the start-finish flag,the effect on the engine speed and excess air coefficient at the start of the gasoline engine was studied.The experimental results show that the start-up time of the engine is proportional to the start-stop-end speed,which means that the higher the rotate speed is,the longer start-up time of engine is.In order to take the reliability and time into account when the engine starts,the speed o f the final start end flag was determined at 610 RPM;(4)The starting oil correction coefficient and the ignition timing were changed respectively,and their influence on the rotation speed and excess air ratio of the gasoline engine at startup was studied.The test results show that in a certain range,the start-up time decreases first and then increases with the increase of the start-up fuel injection correction coefficient,and the start-up time of the car engine increases with the advance of the intake valve start-up time.(5)The three-high test for cold start calibration was performed on the calibration vehicle,including the summer high temperature test and the winter high cold calibration test.For the problems in the calibration test process,the optimization and control strategy for the engine cold start and post-start phases are adjusted so that the engine start performance is gradually optimized.