Continuous Variable Valve Timing - Early Intake Valve Closing

Early Intake Valve Closing

Another way to decrease the pumping losses associated with low engine speed, high vacuum conditions is by closing the intake valve earlier than normal. This involves closing the intake valve midway through the intake stroke. Air/fuel demands are so low at low-load conditions and the work required to fill the cylinder is relatively high, so Early intake valve closing greatly reduces pumping losses. Studies have shown early intake valve closing to reduce pumping losses by 40%, as well as to increase fuel economy by 7%. It also has reduced NO emissions by 24% at partial load conditions. A possible downside to early intake valve closing is that it significantly lowers the temperature of the combustion chamber, which can increase hydrocarbon emissions.