Fiat Multiair engine - Development of Fiat Multiair system

Fiat Multiair engine


After the presentation UniJet and MultiJet diesel engines, Fiat The group represents a whole new generation of gasoline engines, which should make significant improvements in terms of efficiency (more power, lower consumption and harmful emissions).

Fiat The group does after the presentation UniJet and MultiJet technology, has established itself as one of the world's leading companies for the production of clean, economical and environmentally friendly diesel engines.

Now, it's up to the gasoline engines to be modernized. MultiAir is expected to deliver even more power, lower consumption and less CO2 emissions by about 10-25%, while other harmful emissions should be reduced by up to 60%.


- Increase maximum power by about 10% thanks to the use of a new, optimized to increase power, camshaft profile.

- Increase available torque at low revs by up to 15% thanks to a special program of early closing of the intake valves, in order to maximize the utilization of air in the cylinders.

- Elimination of losses, produced by the gas station, which should reduce consumption by about 10%, regardless of whether it is atmospheric or turbo engines.

- The reduced-volume MultiAir engine with turbochargers has up to 25% lower consumption than the classic atmospheric engine of appropriate performance.

- Special programs for control of valve operation and gas recirculation while the engine is cold, which are realized by reopening the intake valves during the exhaust phase of engine operation. The result should be a 40% reduction in harmful emissions for unburned hydrocarbon and carbon monoxide (HC / CO), and up to a 60% reduction in nitrogen (NOx) emissions.

- Constant pressure on the intake manifold for atmospheric and turbo engines, very fast control of air flow by individual cylinders will enable fast response of the engine to the gas command and, thus, greater driving pleasure.

It should be emphasized that MultiAir technology can be applied to any internal combustion engine no matter what the fuel in question. This technology can (and probably will be) used with diesel engines to reduce harmful NOx emissions as well as make diesel particulate filters even more efficient.

In short, engines equipped with Fiat MultiAir technology will be more powerful, have better response at all rpm, use less mustard and have less harmful emissions. The new technology will allow Fiat Group to maintain its leading position as a manufacturer with the most economical product range.

The first engine to be equipped with MultiAir technology will be the atmospheric 1,4 16V engine, which will be found in the Alfa Romeo MiTo model at the end of 2009.



Over the past decade, the development of comm-rail direct diesel injection technology has marked a real milestone in the production of passenger car engines. The Fiat Group has decided to try to improve gasoline engines in the same way.

Unlike diesel engines, in which it was crucial to control the mode, time and amount of fuel injected, in gasoline engines the key is to control the air necessary to burn the fuel.

The MultiAir system measures the air flow at the inlet to the cylinder chamber itself, using advanced control and control of the intake valves.

Fiat decided to operate the valves with the latest generation of electro-hydraulic accumulators, instead of using solenoid ones, which have a very poor reaction time and, therefore, preclude accurate and accurate engine management.

In addition, the electro-hydraulic valve control system requires very little energy, is very cheap to manufacture and is reliable.

Fiat Multiair engine


The basic principle of the new intake valve control system is the following: the piston, whose motion is controlled by the intake camshaft, is connected to the intake valve by a hydraulic connection controlled by the solenoid.

Fiat Multiair engine

When the solenoid is "closed", the hydraulics act as a solid body, so that the connection between the valve and the intake camshaft is directly established, so the intake valve opens and closes as required by the camshaft.

When the solenoid is "open", the camshaft connection does not exist so that the intake valve is controlled by a classic spring.Fiat Multiair engine

Controlling the time and length of opening and closing solenoids virtually controls the operation of the engine and allows optimum engine performance in a wide variety of situations.

If maximum engine power is desired, the solenoid is always open, and the maximum opening of the intake valve is achieved by a camshaft, which is specially designed to allow maximum power at high rpm.

At low rpm, the solenoid opens at the rims of the cam profile to allow the suction valve to be opened briefly, which prevents air from flowing back from the cylinders and maximizes the amount of air in the cylinders.

When the engine is partially loaded, the solenoid opens early - so that the intake valve is only partially open, which controls the amount of air depending on how much torque is needed at a given moment.



As always, the first generation of technology never takes full advantage of the possibilities. For the future it is planned:

- Integration of MultiAir airflow control with direct gasoline injection, to further improve the speed of engine response to commands and increase economy.

- Introduction of even more complex intake valve opening control programs, in order to further reduce harmful emissions.

- Improved compatibility of MultiAir systems with turbochargers, in order to take full advantage of the specifics of the turbo engine.

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