What is CVVD?
Hyundai Motor Group has launched the world’s first Continuously Variable Valve Duration (CVVD) technology to be featured in future Hyundai and Kia vehicles.
The innovation was revealed at Hyundai Motor Studio Goyang, South Korea, alongside the Smartstream G1.6 T-GDi the first engine to feature the technology.
CVVD optimizes both engine performance and fuel efficiency while also being eco-friendly. The valve control technology controls the duration of valve opening and closing according to driving conditions, achieving a 4% boost in performance and a 5% improvement in fuel efficiency. Furthermore, the technology cuts emissions by 12%.
Continuously Variable Valve Duration (CVVD)
An internal combustion engine’s performance and efficiency have been administered by variable valve control technology that adjusts the timing of valve opening and closing and depth of the valve’s opening, with engine power produced through the fuel intake-compression-expansion-exhaustion cycle.
Typical variable valve control technologies manage the timing of the valve’s opening and or control the volume of air admitted by adjusting the depth of the opening. Previous variable valve control technologies could not regulate valve duration, as the valve’s closing timing was subordinate to opening timing and could not respond to diverse driving situations. CVVD takes the technology in a new direction by adjusting how long a valve is open.
When the vehicle is maintaining a constant speed and requires low engine output, CVVD holds open the intake valve until the middle of the compression stroke and from that point holds it closed until near the end of the compression stroke. This helps to improve fuel efficiency by reducing the resistance caused by compression. On the other hand, when engine output is high, such as when the car is driving at a high speed, the intake valve is closed at the beginning of the compression stroke to maximize the amount of air used for the explosion, enhancing torque to improve acceleration.
Engine valves are either for intake or exhaust. The intake valve opens during the intake stroke to draw the fuel-oxygen mixture into the combustion chamber. The Exhaust valve opens during the exhaust stroke to discharge the expanded and oxidated gas out of the combustion chamber. Engine valves open and close in less than 0.02 seconds and undergo about 100 million cycles in the engine’s lifetime.
Although the open-close cycles occur in a couple of hundredths of a second, the cycles are important determining factors of an engine’s power. This is because combustion requires a certain ratio of oxygen from the air; air which can enter and exit only through the valves. The turbocharging technology that has become commonplace in engines is based on forcing in or charging the combustion chamber with an extra gust of air.
Here, duration specifically means the duration of the valve event, optimized to the operation of the engine. The Hyundai Motor Group successfully created the most simply structured, mechanically implemented CVVD mechanism, through countless iterations.
The CVVD system consists of a variable control unit and a drive motor on the camshaft. While ECU turns the CVVD drive motor up to 6000rpm, the variable rotating adjuster moves up and down in 0.5 seconds, and shifts the contact point of the cam lobe, determining how long a valve is open.
CVVD cams share similarities with existing engine cams, but the adjuster link shifts the axis and adjusts cam revolution speeds. Depending on how long the intake and exhaust valves stay open or closed, there are up to 1400 settings that the CVVD system can select from.
“The development of the CVVD technology is a good example of how Hyundai Motor Group is strengthening our powertrain technology. We will continue our innovation efforts to bring forth paradigm shifts and ensure the sustainability of our business model”. Said Albert Biermann President and Head of Research and Development Division at Hyundai Motor Group