The Hyundai Motor Group today revealed details of the continuously variable valve duration system (CVVD) that will debut on the 2020 Hyundai Sonata's 1.6L Smartstream turbo engine when that car goes on sale later this year.

Dubbed a world first by its maker, CVVD evolves the concept of variable valve timing by adding the ability to vary how long the valves remain open. Current variable valve timing systems can open valves earlier or later and change the width of the valve opening relative to the engine's combustion cycle, but only for a fixed duration.

Hyundai says its CVVD system works on the intake valves and can keep them open through part of the compression stroke in light-load situations. By reducing the amount of resistance the pistons encounter during the compression stroke, Hyundai says CVVD boosts fuel efficiency by 5 percent and performance by 4 percent, while cutting tailpipe emissions by 12 percent.

At wider throttle openings, such as at higher speeds and during acceleration, the intake valves close earlier at the start of the compression stroke to maximize torque production.

Modern engines operate on a four-stroke cycle that includes intake, compression, expansion/power and exhaust strokes for each piston. Variable valve control technology allows an engine's control systems to reduce emissions or enhance performance depending on the driving situation.

In the new Sonata, the Smartstream 1.6L engine will make 180 hp and 195 lb-ft of torque mated with an eight-speed automatic transmission. Following its Sonata debut, the CVVD 1.6L turbo will be rolled out in other Hyundai and Kia models.