1980-06-01

Controlling Engine Load by Means of Late Intake-Valve Closing 800794

Varying the timing of intake-valve closing was examined on a single-cylinder engine as a means for controlling the load of a homogeneous-charge spark-ignition engine. The engine was operated unthrottled, with load control obtained by holding the intake valve open during a portion of the compression stroke. This allowed the piston to push part of the cylinder charge back into the intake manifold.Results showed that to achieve the range of load control required for vehicular operation, late intake-valve closing would have to be combined with variable-density throttling. Comparisons to a conventional engine showed the late intake-valve-closing engine to have (1) lower pumping losses, (2) lower specific fuel consumption, (3) lower nitric oxide emissions, and (4) similar HC emissions. However, the fuel-economy benefit offered by this load-control concept would be reduced by the frictional losses of a control mechanism. The current trend toward lower vehicular power/weight ratios also would diminish the impetus for this approach.

SAE MOBILUS

Subscribers can view annotate, and download all of SAE's content. Learn More »

Access SAE MOBILUS »

Members save up to 43% off list price.
Login to see discount.
Special Offer: Purchase more aerospace standards and aerospace material specifications and save! AeroPaks off a customized subscription plan that lets you pay for just the documents that you need, when you need them.
X