Fiat variable valve control system—— MultiAir

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In the car exhibition of Geneva in 2009, Fiat officially released its research achievements on variable valve technology.It is assembled to the engines of 1.4 FIRE series and the subsequent  double-cylindered engine of 900CC.

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It can be apparently seen from the picture, the system of MultiAir is indeed quite simple. A liquid chamber is put above the air valve, and connects with the solenoid valve.The solenoid valve adjusts the oil mass transferred to liquid chamber according to different working conditions through Ecu signals. The plunger powered by camshaft controls the valve on and off through pushing the oil in the liquid chamber.

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From this simplified structure sketch, we can apparently know how the whole system works. But camshaft and plunger are actually put on one side of the camshaft of the valve exhaust. And the cam pushes the plunger with a rocker arms, thus opening the air valve through the pressure changes in the liquid chamber. When  Multiair starts to work, the magnetic valve provide the liquid chamber moderate oil mass through ECU signals, and then the  magnetic valve itself.At this time, the volume of the oil in the liquid chamber is constant, so the plunger connecting the liquid chamber can transfer the pressure from the exhaust cam shaft to the air valve, opening the air valve.

The most striking advantage of MultiAir is that it removes the admission cam shaft and the air damper, and uses a air valve to  control the air dose in the cylinder stator. Also, the remove of admission cam shaft simplifies the structure of cylinder cover and lightens the engine, and the remove of air damper greatly reduces bumping loss and increases the response speed of the engine.In addition,the lightweight and the  miniaturization design in engine is also a big advantage of MultiAir. Because it removes the air damper, and adopts only one camshaft, which makes it superior to traditional DOHC overhead double camshaft engine

 

References:

http://en.wikipedia.org/wiki/MultiAir

http://www.caranddriver.com/features/fiats-multiair-valve-lift-system-explained

http://www.motortrend.com/features/auto_news/2011/1103_chrysler_engines_to_get_fiat_multiair_technology/

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