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This paper describes the principles, effects and the potentials of impulse charging systems applied to SI and Diesel engines. In general, impulse charging is realized by closing the inlet port upstream of the inlet valve during the intake stroke with an additional switching device. The piston, moving towards bottom dead center, generates a vacuum inside the combustion chamber and inlet port. By opening the switching device abruptly, the sub-atmospheric pressure level induces an enhanced volumetric efficiency due to the significantly increased gas dynamic effects in the intake manifold. One major advantage of impulse charging in comparison to the well known supercharging techniques lies in the dynamic behavior. The charging effect can be realized within one engine cycle. Furthermore, impulse charging provides high low-end torque, a nearly constant torque over a wide engine speed range with charging rates from 20% to 30%.

This paper reports the results of theoretical and experimental investigations in the field of variable intake - valve control of spark-ignition engines. Different degrees of freedom for a variable intake profile such as variable intake opening and closing events, variable valve lift, as well as the deactivation of one of the intake valves per cylinder of a multi-valve engine are considered and evaluated concerning their potential to reduce pumping losses, to support mixture formation, and to improve combustion. The investigations show that additional efforts are necessary to convert the potential of minimized pumping losses due to unthrottled SI-engine load control into reduced fuel consumption and good driveability. Increased gas velocities during intake for low engine speed and load and adjusted residual-gas fractions according to the different operating conditions prove to be very efficient parameters to improve engine performance under unthrottled conditions.