An overhead camshaft, which directly drives the exhaust valves on one side and indirectly the others, has been around for a very long time. What is new with this system is that in this case the intake valves are not actuated mechanically but hydraulically.

In the picture above, one clearly sees the channel from the pump element at the only inlet cam per cylinder to the two elements above the two intake valves. The valve, which is also visible, can open a connection to the oil circuit for a short period of time.

It is not promised too much if one compares it with already existing fully variable systems already in use e.g. in BMWs. In contrast to these, even fractions of the air volume one other another are possible (picture below, last diagram). The remaining diagrams show how strongly the system can be adapted to the respective operating range.

The first saving effect is significant by the always open throttle valve. The system is available for different cylinder numbers. The question remains, why a system without a camshaft only based on valve opening due to oil pressure is possible.

Fiat Powertrain Technologies presents Multi Air, the electronic control of air supply and combustion. In conventional internal combustion engines, the intake valve and thus the amount of intake air are controlled by the rotating camshaft. Disadvantage: loss of energy and too slow reaction to the change in operating conditions.

MultiAir is the new electronic system that ensures a more dynamic control of the intake air, for every cylinder and every stroke. This electrohydraulic technology is based on a combination of high pressure oil between the camshaft and intake valve, controlled by an electronically controlled solenoid valve.

This allows extremely flexible response to the air requirement of the engine. Variable timing is needed to increase the efficiency of an internal combustion engine, performance, fuel consumption and emissions. The full valve opening common to conventional engines is only used with MultiAir when full power is needed.

When the engine is started to idle, the intake opens later in favor of a higher airspeed, which promotes mixture formation. At moderate torque requirements, the intake opens and closes early. This favors the utilization of the volume, pumping losses and backflow into the suction system are avoided.

The multiple opening comes at idle, e.g. at stop-and-go in the city before. Thus, the system presents itself as ready for Euro 5 and 6, facilitated starting conditions, low consumption, responsive and with maximum motivation. 07/17