Donald J. Pozniak

A lost-motion, variable-valve-timing system for automotive piston engines

A simple, passive, lost-motion mechanism for varying the timings of engine valve opening and closing events has been developed and evaluated. The mechanism was found to be durable and precise in its control. When applied to a high-specific-output engine, the mechanism allowed much lower idle speeds and reduced idle fuel consumption without compromising high-speed power. However, valve-train noise was increased moderately at low engine speeds. When applied to a low-speed passenger-car engine with a compatible camshaft to reduce valve-train noise, the mechanism provided idle quality, fuel consumption, and vehicle performance roughly equivalent to those for the same engine operating with conventional fixed valve-timing. Thus, the potential advantages of this type of variable valve-timing appear to be confined to an engine system which is designed for high power output over a wide speed range.

The Design of an Engine-Flywheel Hybrid Drive System for a Passenger Car

The quest to improve the fuel economy of General Motors passenger cars has led to the investigation of an engine-flywheel hybrid powertrain at the GM Research Laboratories (GMR). An engine-flywheel system was designed for a compact car and its performance was predicted analytically. The sytem was estimated to achieve an improvement in EPA composite fuel economy of 13 per cent ooer a 1984 production compact car. This margin of improvement was judged insuficient to justify the complex drivetrain, and, therefore, a prototype system was not built. However, the current potential of engine-flywheel hybrids for GM passenger car applications has been defined, and the technology areas requiring additional research attention have been identified.