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.
Read more about this topic: Continuous Variable Valve Timing
Famous quotes containing the words early and/or closing:
“Here is this vast, savage, howling mother of ours, Nature, lying all around, with such beauty, and such affection for her children, as the leopard; and yet we are so early weaned from her breast to society, to that culture which is exclusively an interaction of man on man,—a sort of breeding in and in, which produces at most a merely English nobility, a civilization destined to have a speedy limit.”
—Henry David Thoreau (1817–1862)
“And if the stage-dark head rehearse
The fifth act of the closing night,
Why, cut it off, piece after piece,
And throw the tough cortex away....”
—Allen Tate (1899–1979)