Fiat Shows New Super-Efficient Variable-Valve Timing/Lift System

By Editors on March 6, 2009 9:15 AM

Fiat displayed a new and improved take on the variable valve-timing and lift design theme at Geneva, where it unveiled a trick electro-hydraulic actuation system called Multiair. According to the automaker, the Multiair system can optimize both the intake and combustion processes for each individual cylinder on a stroke-by-stroke basis. This ability creates a win-win-win opportunity in which power and economy can be significantly increased while emissions are dramatically reduced on both naturally aspirated and turbocharged engines. In contrast to some earlier variable-valve packages that utilized electromagnetic actuation, the practical appeal of Fiat's new electro-hydraulic setup is that it's far cheaper and more reliable while requiring less power to operate.

The heart of the Multiair system is a small piston that's actuated by a mechanical cam which is connected to each intake valve via a hydraulic chamber. This, in turn, is controlled by a normally open on/off solenoid valve that instantaneously responds to a series of computer commands to vary the intake's timing and lift schedule in a manner that ideally complements differing load conditions, from feather-footing to full throttle. Fiat claims the real-world benefits of Multiair technology are impressive, to say the least. Maximum engine power can be increased by up to 10 percent while its ability to eliminate pumping losses can reduce fuel consumption by 10-25 percent. In addition to making an engine more responsive to throttle input, Multiair's more precise valve-control mapping during warm-up coupled with internal exhaust gas recirculation gains trim hydrocarbon (HC) and carbon dioxide CO2 emissions by up to 40 percent and cut oxides of nitrogen (NOx) by up to 60 percent.

Fiat's first wide-scale application of Multiair will be on its "Fire" family of 1.4-liter 16-valve four-cylinder gasoline engines, which will be produced in both naturally aspirated and turbo from. The firm also is developing an all-new 900cc two-cylinder Small Gasoline Engine (SGE) family that's specifically designed to take full advantage of the Multiair system. One turbocharged version of the new SGE line will be fueled by compressed natural gas (CNG).