Research On The Variable Intake Manifold And Variable Valve Timing Of EFI Engine

Intake system and air distribution system are key components of electronic fuel injection (EFI) gasoline engine, which directly effect engine volumetric efficiency and the economic and power performance of EFI gasoline engine. With the rapid development of electronic control technology and the new mechanisms are constantly emerging, variable parameter design of intake system and air distribution system on EFI gasoline engine becomes possible. Variable length intake manifold can improve the volumetric efficiency of EFI gasoline engine by fluctuation effect in the broad engine speed range; Best phase angle is provided by variable valve timing, which enhances the performance of the EFI gasoline engine in full load conditions.This paper analyzed all kinds of domestic and international variable intake system and variable valve timing system. Based on 474 EFI gasoline engine, simulation model is established by one-dimensional simulation software AVL-BOOST, two-stage variable technology on intake manifold and valve timing are adopted in optimization design by comparing the simulation data and experimental data. The optimization parameters of variable intake manifold include the manifold length and diameter, while the optimization parameters of variable valve timing include intake advance angle, intake late closed angle, exhaust advance angle and exhaust late closed angle.The simulation-result of the variable intake manifold optimization design shows that:EFI gasoline engine should use slightness intake manifold in low-speed, while switch to thick short intake manifold in high speed. The average performance of variable intake manifold length and diameter can be adjusted is better than the variable length intake manifold and variable diameter intake manifold. The power and torque of the variable intake manifold can be increased by up to12.79%, volumetric efficiency can be enhanced up to14.55%, brake specific fuel consumption (BSFC) also can be decreased.The simulation result of the variable valve timing system optimization design shows that: Exhaust late closed angle and intake late closed angle have the greatest influence on the average performance of EFI gasoline engine. The volumetric efficiency, power and torque of variable intake late closed angle valve-train can be separately increased by up to 3.81%,3.13% and 3.08%, average BSFC can be reduced about 3.1%; The volumetric efficiency, power and torque of variable exhaust late closed angle valve-train can be separately enhanced up to 3.3%, 2.9% and 2.89%, average BSFC can be reduced about 2.8%. As to 474 EFI gasoline engine, variable exhaust late closed angle valve-train is better than variable intake late closed angle valve-train, while the difference is not very significant. After variable intake manifold and variable valve timing system are joint matched, the volumetric efficiency can be enhanced up to 15.04%, power and torque can be increased by up to15.43%, average BSFC can be reduced about 3.5%.Based on the computer aided analysis method, is used to one-dimension engine working process cycle simulation numerical calculation method, analyze the influence of different length and diameter of intake manifold and phase angle of valve-train on EFI gasoline engine. This paper aimed to be instructive on the engine simulation, the design analysis of variable intake system and variable valve timing system.