By the combination of 3D simulation and bench test

effects of medium and high tumble ratio combustion system of a three-cylinder turbocharged port-injection gasoline engine on the engine performance of combustion

power and fuel consumption were studied under full load conditions. Results show that the value of tumble ratio directly affects the moment of turbulent kinetic energy peak and the center of turbulent kinetic energy

which affects the flame development and propagation. The excessively high tumble ratio will cause the center of turbulent kinetic energy to eccentric and affect the flame propagation. The medium tumble ratio combustion system A facilitates the formation of flame core and the flame propagation

shortening the total combustion duration and improving the thermal efficiency. At low-to-medium speeds

the crank angle of 50% mass fraction burned （MBF50） by the medium tumble ratio combustion system A is 3.4°ahead of the value of the high tumble ratio combustion system B

while the indicated mean pressure cycle variation can be maintained at 3%.