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Collaboration between the Schaeffler Group and Fiat Powertrain has resulted in UniAir, an engine system that is claimed to be the world’s first fully variable hydraulic valve control system.

UniAir will make its debut on Fiat’s Alfa MiTo 1.4 MultiAir.

As well as offering car manufacturers a more compact valve-control system, UniAir will help the automotive industry meet future CO2 emissions targets for passenger cars, according to Schaeffler.

UniAir provides improvements in start-up, part-load and acceleration behaviour of the vehicle.

During the engine warm-up phase, for example, hydrocarbon emissions are up to 40 per cent less, and nitrogen oxide is reduced by up to 60 per cent.

In addition, UniAir is said to offer an improved driving experience through more power, higher engine torques and optimised engine response.

Car manufacturers are expected to be impressed by the fact that UniAir enables car engines to be downsized.

Fiat uses UniAir in its four-cylinder Fire series of engines and in its small-volume two-cylinder engines that are in development.

As well as petrol engines, UniAir will also be available for diesel-engine applications.

Developed for series production by Schaeffler, UniAir refers to the system as MultiAir.

UniAir/MultiAir is also based on an invention by the Centro Ricerche Fiat (CRF).

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.

UniAir allows variations in the valve stroke and in the opening and closing of valves several times during one cycle, at different points in time.

Therefore, the system is said to expand the potential of traditional valve-train mechanisms.

UniAir can provide full coverage of every conceivable airflow possibility, from zero lift to maximum lift, dictated by the camshaft lobe for each individual cylinder or valve.

With the de-throttling of the engine, UniAir can provide early intake-valve closing or late intake-valve opening in order to maximise engine breathing relative to certain engine speed and load conditions.

UniAir is said to offer unique valve lift events for every valve – individually and cycle-to-cycle.

In contrast, an electromechanically actuated, fully variable valve train requires several cam events to achieve the same lift differential.

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