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Fiat Breathing Easy With MultiAir
By Tom Murphy
WardsAuto.com, Mar 26, 2010 9:00 AM
TORINO – Here in northern Italy, surrounded by the snow-covered peaks of the Italian Alps, winter days can be icy and bleak, devoid of the electrifying thrill that charged the region when it hosted the Winter Olympics four years ago.
But the halls of Fiat Powertrain Technologies’ Central Research lab, which pioneered the now-ubiquitous high-pressure common rail for diesel engines, as well as the automated manual transmission, are buzzing with energy because engineers and executives know they are sitting on a goldmine.
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After 15 years of development, Fiat’s MultiAir induction technology, which takes variable valve timing to a whole new level of flexibility, has made it to prime time, introduced late last year in the Alfa Romeo MiTo (pronounced ME-toe) in Europe.
As many as 1 million Fiat engines annually will incorporate MultiAir technology within the next three years for the European market, Lucio Bernard, Fiat’s diesel engine director, tells Ward’s.
Americans will get to experience MultiAir for the first time in the fourth quarter when the Fiat 500 city car goes on sale, powered by a 1.4L FIRE engine being built in Dundee, MI.
Fiat is confident MultiAir will revolutionize engine valve control in the same way common rail now is standard on every new light-vehicle diesel engine.
“Eventually all gasoline engines will have this,” declares Richard Gadeselli, vice president-communications for Fiat Automobiles SpA. “We’re at the start of a rollout.”
The auto maker says MultiAir delivers a 10% boost in power, 15% increase in low-end torque and up to 10% improvement in fuel economy for both normally aspirated and turbocharged engines. Although the first applications are for gasoline engines, MultiAir also is compatible with diesel.
The fuel-efficiency gain can jump to 25% if, say, a V-6 were replaced by a turbocharged 4-cyl.
Variable valve timing is not a new concept.
Here at the Central Research labs, Fiat’s Giovanni Torazza developed a system in the late 1960s that used hydraulic pressure to vary the fulcrum of the cam followers. It became the first fully functional VVT system patented by an auto maker.
But many industry observers credit Honda Motor Co. Ltd. with bringing VVT to the masses with its VTEC system, which debuted in 1983 and enabled electronic switching between two cam profiles, depending on driver inputs.
Cutaway of Fiat’s 1.4L FIRE engine shows MultiAir system. One camshaft controls both intake and exhaust valves.
Since then, with the proliferation of multi-valve engines, auto makers have pursued various routes to VVT as a way to boost performance and fuel economy and reduce pumping losses. Electro-magnetic actuation was researched heavily but eventually abandoned as inefficient and unreliable.
Then came simpler electro-mechanical concepts that usually employed cam phasers to allow control of both valve lift and phase.
More advanced electro-mechanical valve-control systems have flourished over the past decade, with successful production launches (and upgrades) from BMW AG (Valvetronic), Toyota Motor Corp. (VVT with Intelligence) and Nissan Motor Co. Ltd. (Variable Valve Event and Lift).
In the meantime, Fiat changed gears in the mid-1990s, switching its VVT research efforts to electro-hydraulic actuation, which had provided the foundation for Fiat’s patented common-rail fuel delivery for diesel engines.
The goal was to achieve unprecedented levels of valve control. Cylinder by cylinder and stroke by stroke, Fiat engineers wanted the ability to precisely meter how much air enters the combustion chamber, dictated by the particular driving mode.
Fiat believed electro-mechanical systems gaining popularity didn’t offer enough flexibility in valve control and were not modular, nor compatible with diesel engines.
Years of research revealed electro-hydraulic actuation would be relatively simple, reliable and inexpensive, and power requirements would be minimal.
Enter the MultiAir system, also known as Fully Variable Valve Actuation, which works only on the intake valves. MultiAir needs only one overhead camshaft, with lobes to govern both exhaust and intake openings.
Fiat explains the system this way: Variable valve actuators, filled with conventional engine oil drawn from the sump, are positioned between the camshaft and each intake valve. With every rotation of the camshaft, a solenoid valve connected to an electronic control unit is energized, regulating the quantity of oil pumped by the cam action to the actuator or a reservoir.
How wide the intake valves open for every combustion cycle depends on how much oil has been pumped to the actuator. The timing of the valve openings changes constantly, based on pedal inputs and driving conditions.
With this unlimited number of air-management strategies, Fiat says MultiAir allows each cylinder to operate independent of the next, allowing engines to react much more quickly to changes in driver inputs.
There are five modes behind MultiAir, each one tailored to a particular driving cycle:
Late Opening: When the vehicle is started and at idle, a partial valve opening is achieved by closing the solenoid valve while the mechanical cam action already has started. The result: Air enters the combustion chamber at higher velocity, achieving higher in-cylinder turbulence.
Early Closing: For low-rpm torque, the solenoid valve is opened near the end of the cam profile, causing the intake valve to close early, eliminating unwanted backflow into the intake manifold and trapping the maximum amount of air in the cylinder.
Partial Load:The solenoid valve opens early, causing partial valve openings to control the trapped air mass as a function of the required torque.
High-response solenoid enables infinitely variable intake valve actuation in MultiAir system.
MultiLift: In stop-and-go traffic, the system allows the intake valve to open twice for each intake stroke, enhancing turbulence and combustion rates at low loads. This mode is designed mainly to save fuel.
Full Opening: For maximum power on the highway, the solenoid valve is always closed and the camshaft provides full lift of the valves, as if the MultiAir system were not on board at all.
But the system operates in more than just these five principal modes.
“For each of these five modes and strategies, there are infinite, continuously variable valve-lift profiles,” Bernard says. “It is in my opinion quite correct to say that Multiair enables infinitely variable control of the valvetrain.”
Next generations of the technology will add new valve-control modes.
For instance, Bernard says an engine with MultiAir could do without a conventional exhaust-gas recirculation valve. That function could be handled entirely by a secondary lobe on the intake cam profile, allowing the opening of the intake valves during the exhaust stroke.
This would allow part of the exhaust gas to be stored in the intake ducts, then sucked into the cylinder in the following intake stroke.
It’s difficult to imagine so much happening – and so many changes occurring – in the span of milliseconds. To the driver, the underhood machinations are nearly imperceptible.
On a short drive here, a MultiAir-equipped Alfa Romeo MiTo (aptly named by combining the names of neighboring cities Milano and Torino) is incredibly quiet and capable, integrating a smooth-functioning stop/start system.
The turbocharged 1.4L FIRE engine makes 135 hp on paper, but it feels like much more, with loads of low-end torque. It freely sprints to the redline, without being thrashy and without sounding like an overtaxed “4-banger.” Whatever MultiAir does, it works.
The price is right for the entry-level Italian luxury car, E19,000 ($25,370), and the estimated fuel economy is astounding: 42 mpg (5.6 L/100 km). For context, consider Mini a competitor.
In this Alfa Romeo application – with a 6-speed manual transmission – the 1.4L turbo is one of the world’s most enjoyable 4-cyl. engines.
So where to now for MultiAir?
Fiat could start printing money by selling licenses allowing other auto makers to use the technology. But that won’t happen until the company has a big head start on its rivals, Gadeselli says.
“The primary error we made with the development of common-rail diesel was that we licensed it immediately, which meant we didn’t have any proprietary lead,” he says. “We came out with a car, and immediately after, all our competitors came out with it.”
Within each of the five intake modes, there are infinite valve-lift profiles. Fiat says future generations of MultiAir will introduce additional valve modes, enabling further improvements.
Fiat won’t make the same mistake twice, executives promise. But Bernard suggests Fiat might be willing to negotiate in two or three years.
By virtue of Fiat’s recently acquired 20% stake in Chrysler Group LLC, North America will get MultiAir by year’s end – before other markets such as South America and Asia, where Fiat already is firmly entrenched.
The 500, to be produced in Toluca, Mexico, goes on sale at the end of the year in the U.S. with the naturally aspirated 100-hp 1.4L MultiAir FIRE engine, about the same time a 170-hp turbocharged version of the same engine arrives.
Beyond the 1.4L, Fiat has said MultiAir will appear on 2.0L and 2.4L Chrysler World Engines, although applications have not been confirmed. Chrysler has said the MultiAir 2.4L produces 190 hp.
The technology also will be applied to Chrysler’s all-new 280-hp 3.6L Pentastar (aka “Phoenix”) DOHC V-6, appearing first in the all-new Jeep Grand Cherokee later this year. The engine is expected to have variable valve timing on both intake and exhaust valves.
In Europe, Fiat sells three MultiAir versions of the 1.4L FIRE engine, producing between 105 hp and 170 hp.
In addition to the MiTo, MultiAir engines are available in the Fiat Punto and, by June, the Fiat Bravo.
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In September, the 500 will be available in Europe with an all-new 85-hp 2-cyl. 0.9L TwinAir turbocharged gasoline engine that emits 30% less carbon dioxide than an engine of equal performance.
Afterward, a naturally aspirated 65-hp version of the TwinAir engine is due, followed by another turbocharged 105-hp version. Also in the powertrain plan is a compressed-natural gas version of the TwinAir, Bernard says.
Fiat currently produces MultiAir FIRE engines at its plant in Termoli, Italy. Production of the new TwinAir engine will ramp up this summer at Fiat’s plant in Bielsko-Biala, Poland.
Producing the MultiAir actuators for Fiat under a licensing agreement is German supplier Schaeffler KG, which ships the units directly to the Termoli engine plant.
As volumes increase, Bernard says he hopes component production can be done closer to the engine plants.
Bernard declines to specify the additional costs associated with MultiAir, but he says they are reasonable, partly because the technology allows for certain components to be eliminated, such as one of the camshafts.
Gadeselli realizes Fiat cannot view MultiAir primarily as a tool to meet strict new fuel-economy and CO2 emissions requirements.
“People buy Italian cars because they’re nice to drive and offer good performance,” he says. “We’re not forsaking that part of our DNA in this singular drive to reduce CO2. That’s why MultiAir is such a key technology for us. It’s actually doing everything.”
Fiat Powertrain Technologies
20,000 employees and 22 assembly plants
17 research and development facilities worldwide
400 researchers and physicists at Torino Central Research labs
3 million engines and 2.5 million transmissions produced annually
Engine sizes range from 0.9L to 20.0L for marine applications
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