Fiat’s MultiAir System: Valve Control for Fiat and Chrysler Engines

Fiat MultiAir system

Fiat MultiAirMultiAir is Fiat’s variable valve timing and lift technology; it allows for separate timing of each cylinder. Engines sold in North America with MultiAir include Chrysler’s TigerShark 2.4 and the 1.4 liter Fiat “FIRE” engine, both standard and turbocharged.

The system uses electro-hydraulic valve actuators; a solenoid energized with each rotation of the camshaft regulates the amount of oil sent to the actuator, which controls the amount of lift from completely closed to completely open. Rather than having a limited number of positions between open and closed, there is infinite variation over the opening of the intake valves.

Unlike competing systems, MultiAir allows for each individual cylinder’s valves to be adjusted independently, for faster responses.

Valve timing is also adjusted, with the system keeping the valve open as long as needed. The setup replaces the conventional throttle valve, too, providing more dynamic and direct control over combustion and airflow. MultiAir technology can be adapted to diesels for enhanced NOx control.

Chrysler claims that power can be increased by up to 10% because of the ability to use a better cam profile, with low-end torque increased by up to 15% due to direct control over valve opening.

Greater mass air pressure increases acceleration, while cutting up to 7.5% of fuel consumption results from lower pumping losses. Cold starting is also improved.

Fiat FIRE

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