A fully variable hydraulic valve actuation using early intake valve closing (EIVC) mode was developed and assembled on a SD2100TA diesel engine to adjust intake mass flow and effective compression ratio in a large speed range. The intake and combustion characteristics of the modified engine were investigated. The experimental results show that

compared with the throttle valve control mode

the pumping loss is reduced substantially and the mean cylinder temperature is decreased in EIVC mode

which is beneficial to low temperature combustion (LTC). With the advance of intake valve closing timing (IVCT)

the effective compression ratio is decreased

the cylinder pressure and temperature at the end of compression stroke are lowered

the ignition delay is increased

the start of heat release is delayed

the proportion of premixed combustion is increased

the proportion of diffusion combustion is decreased

and the exhaust temperature is decreased because of the reduction in the heat capacity. A significant reduction in the peak pressure is attained providing that there is little variation in indicated thermal efficiency

with which a larger output power is obtained. The peak pressure is reduced by 26% at 1 650 r/min and IMEP of 0.64 MPa when the IVCT is advanced from 30° to -50° in crank angle after BDC.