Future Kia Motors vehicles will feature world-first Continuously Variable Valve Duration (CVVD) engine technology. The innovation has been developed by Hyundai Motor Group, Kia’s parent company, and was revealed alongside the company’s new Smartstream G1.6 T-GDi engine – the first power unit to feature the technology.
CVVD optimises both engine performance and fuel efficiency while also being eco-friendly, says Kia. The valve control technology regulates 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%.
Innovation explained
Until now, an internal combustion engine’s performance and efficiency have been governed by variable valve control technology that adjusts the timing of valve opening and closing and depth of the valve’s opening. Engine power is produced through the fuel intake-compression-expansion-exhaustion cycle.
Typical variable valve control technologies manage the timing of the valve’s opening and closing (as in Continuously Variable Valve Timing – CVVT) or control the volume of air admitted by adjusting the depth of the opening (Continuously Variable Valve Lift – CVVL). 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 the length of time that a valve stays open.
Kia explains: “When the vehicle maintains a constant speed and requires low engine output, CVVD opens the intake valve from the middle to 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 maximise the amount of air used for the explosion, enhancing torque to improve acceleration.”
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