Engine manufacturers have for several years used electronics to control fuel-injection rates in diesel engines. In a demonstration of engine technology earlier this year, International Truck and Engine Corp. unveiled a system that uses electronics to also manage air in the combustion process.

International replaced a conventional engine's mechanical system of camshafts, lifters, pushrods and rocker arms (Figure 1) with an electro-hydraulic system using actuator pistons to open and close the engine valves (Figure 2). This allows control of air to and from the engine without limitations imposed by the mechanical system of cams and levers. Camless technology provides infinitely variable valve timing, which International said should improve durability and driveability, reduce weight and decrease emissions.

The engine technology is the result of a joint venture International formed with Sturman Engine Systems in 1995. The recent demonstration used an International 8100 truck with a 530E diesel engine. According to the company, benefits of camless technology include:

* 40% increase in torque at clutch-engagement speeds, creating a flatter torque curve and resulting in smoother acceleration and faster starts;

* integration of compression-braking technology for greater control over deceleration and less brake wear;

* increased parts reliability and less noise because valve closing rate is controlled with hydraulic actuation and the valves compress gently;

* decreased weight because the camshaft is eliminated and the compression brake is incorporated into the engine instead of added on; and

* increased reliability because the solid-state electronic controls are wear resistant and easier and faster to diagnose compared with mechanical systems.

Low-emission engines As the Environmental Protection Agency continues to tighten clean-air standards, electro-hydraulic air-management technology provides another engineering tool to help meet emissions goals.

"Camless engine technology represents a radical change in the way engines operate," said Patrick Charbonneau, vice president of engine engineering of International's engine group. "We believe applying this technology to air management in diesel engines is the inevitable step to meeting customers' needs while achieving clear-air solutions."

International also has demonstrated what it calls Green Diesel Technology based on the use of ultra-low sulfur (less than 5 parts per million) diesel fuel. Tests of an International 4900 6Yen4 dump truck with a 530E engine, a continuously regenerating trap and ultra-low sulfur diesel fuel indicated a more than 90% decrease in particulate emissions, the company said. Hydrocarbons were reduced below measurable levels and diesel odors were eliminated.