Fully variable hydraulic valve control system cuts CO2 emissions
A collaborative development between Schaeffler and Fiat Powertrain has resulted in the development of a fully variable hydraulic valve control system for use on car engines. The transmission reduces vehicle fuel consumption by up to 25%.
The joint development called UniAir will make its debut on Fiat's Alfa MiTo 1.4 MultiAir. It will deliver improvements to start-up, part load and acceleration behaviour of a vehicle.
UniAir is a cam-actuated, electro-hydraulic valve train system. The fully variable valve control can be used for both petrol and diesel engines and is supplied via the existing engine oil circulation system. For petrol engines, UniAir enables throttle-free, continuously variable, software-based load control across the entire engine map.
With diesel engines, regulation of the temperature of the combustion chamber is achieved due to the precise control of exhaust gas recirculation rates. At the same time, the effective compression ratio in the cylinder can be varied and a homogeneous combustion ensured.
It is hoped that the technology will allow car manufacturers to downsize the engine size. Fiat uses UniAir in its four-cylinder FIRE series of engines and in its small volume two cylinder engines that are currently being developed.
Michael Haas, director advanced engineering and business development at Schaeffler Group Automotive's Engine Systems, says: "The development of the fully variable valve control system to production standard has involved complex efforts in the fields of mechanics, hydraulics and valve control software."
UniAir allows variations in the valve stroke, and also in the opening and closing of valves several times during one cycle, at different points in time. Therefore, the system significantly expands the potential of traditional valve train mechanisms.
