When it's time for maximum power, CVVD closes the valve at the beginning of the compression stroke
By: Evan Williams
July 3, 2019
Hyundai has just announced a new valve timing measure it’s calling a world’s first. The automaker says that its new CVVD will increase performance, boost fuel efficiency, and cut emissions. And it’ll arrive in a new engine that’s set for launch later this year.
The automaker calls the tech continuously variable valve duration. Existing variable valve timing changes when the valves open and close in the combustion cycle, and can even change how far they open. What they couldn’t change was how long the valves would stay open. That’s valve duration.
Hyundai says their new system can adjust how long the valves stay open. Which it says is more effective than just varying the timing of the valvetrain.
At constant speeds and low outputs, CVVD opens the intake valve in the middle of the compression stroke until the end of that stroke. Hyundai says that reduces fuel consumption by reducing losses to compression resistance. It would also reduce the amount of air in the cylinder, thus reducing the amount of fuel needed to burn it.
When it’s time for maximum power, CVVD closes the valve at the beginning of the compression stroke. Maximising how much air, and so fuel, there is in the chamber. Which increases torque and power. The info is short on details, but it appears to shift the center point of the camshaft to alter the opening and closing of the valves.
What’s the difference? Hyundai says 4 percent better performance, 5 percent better fuel efficiency, and 12 percent decreased emissions.
The tech will debut on a new 1.6L turbo-four Hyundai calls the Smartstream G1.6 T-GDI. That engine will develop 180 hp and 195 lb-ft of torque. It’s going to end up in the Hyundai Sonata Turbo, which the automaker says will be introduced in the second half of the year. It’ll appear in more Hyundai and Kia vehicles following that launch.
The new engine has some other efficiency-boosting tricks. Like a low-pressure exhaust gas recirculation. That increases EGR efficiency under high loads. It will also have a new thermal management system to get the engine to temperature more quickly and then keep it there. Plus a new higher-pressure fuel system and lower friction moving parts.