• Mar 7th 2009 at 9:07AM
  • 22
Fiat's not planning to give up its title as the lowest CO2-producing line in Europe any time soon. While diesel engines remain the best choice when carbon emissions are the main concern, the Italian automaker has invested plenty of research and development into its Multiair technology for gasoline powerplants. The latest engines using this tech were unveiled earlier this week at the Geneva Motor Show, as expected.

Nearly all automakers have some form of variable valve technology. Fiat's system is unique in that it uses an electro-hydraulic system to actuate the valves as opposed to the more common electro-mechanical setup. This relatively simple system can alter the timing of the valve's opening and closing in relation to how much power or efficiency is required at any specific moment.

Fiat claims its Multiair technology allows for a 10 percent improvement in horsepower, a 15 percent improvement in low-rpm torque and a 10 percent improvement in fuel efficiency and carbon emissions. Since the powerplant can be made smaller for a given power requirement, further gains are possible over a conventional engine. For a more detailed explanation of how all of this works, click past the break. Thanks for the tip, Jules!

[Source: Fiat]


Fiat Multiair: The Ultimate Air Management Strategy

GENEVA, Switzerland, 4 March, 2009 - Fiat Group and Fiat Powertrain Technolgy unveiled its new air management technology 'Multiair' at the Geneva Motor Show. Multiair is an electro-hydraulic system of engine valves for dynamic and direct control of air and combustion, cylinder by cylinder and stroke by stroke. Thanks to a direct control of the air through the intake engine valves without using the throttle, Multiair helps reducing fuel consumption; and pollutant emissions are likewise reduced through combustion control.

The Fiat Multiair Technology: some history In the last decade, the development of the Common Rail technology for Diesel engines marked a breakthrough in the passenger car market. To be competitive also in the field of gasoline engines, Fiat Group decided to follow the same approach and focus on breakthrough technologies. The aim was to provide customers with substantial benefits in terms of fuel economy and fun-to-drive while maintaining the engine intrinsic comfort characteristics, based on a smooth combustion process and on light structures and components.

The key parameter to control Diesel engine combustion and therefore performance, emissions and fuel consumption is the quantity and characteristics of the fuel injected into cylinders. That is the reason why the Common Rail electronic Diesel fuel injection system was such a fundamental breakthrough in Direct Injection Diesel engine technology.

The key parameter to control gasoline engine combustion, and therefore performance, emissions and fuel consumption, is the quantity and characteristics of the fresh air charge in the cylinders. In conventional gasoline engines the air mass trapped in the cylinders is controlled by keeping the intake valves opening constant and adjusting upstream pressure through a throttle valve. One of the drawbacks of this simple conventional mechanical control is that the engine wastes about 10% of the input energy in pumping the air charge from a lower intake pressure to the atmospheric exhaust pressure.

A fundamental breakthrough in air mass control, and therefore in gasoline engine technology, is based on direct air charge metering at the cylinder inlet ports by means of an advanced electronic actuation and control of the intake valves, while maintaining a constant natural upstream pressure.

Research on this key technology started in the 80's, when engine electronic control technologies reached the stage of mature technologies.

At the beginning world-wide research efforts were focused on the electromagnetic actuation concept, following which valve opening and closing is obtained by alternatively energizing upper and lower magnets with an armature connected to the valve. This actuating principle had the intrinsic appeal of maximum flexibility and dynamic response in valve control, but despite a decade of significant development efforts the main drawbacks of the concept - its being intrinsically not fail-safe and its high energy absorption - could not be fully overcome.

At this point most automotive companies fell back on the development of the simpler, robust and well-known electromechanical concepts, based on the valve lift variation through dedicated mechanisms, usually combined with cam phasers to allow control of both valve lift and phase. The main limitation of these systems is low flexibility in valve opening schedules and a much lower dynamic response; for example all the cylinders of an engine bank are actuated simultaneously thereby excluding any cylinder selective actions. Many similar electromechanical valve control systems were then introduced over the past decade.

In the mid 90's Fiat Group research efforts switched to electro-hydraulic actuation, leveraging on the know-how gained during the Common Rail development. The goal was to reach the desired flexibility of valve opening schedule air mass control on a cylinder-by-cylinder and stroke-by-stroke basis.

The electro-hydraulic variable valve actuation technology developed by Fiat was selected for its relative simplicity, low power requirements, intrinsic fail safe nature and low cost potential.

The Fiat Multiair Technology: how it works

The operating principle of the system, applied to intake valves, is the following: a piston, moved by a mechanical intake cam, is connected to the intake valve through a hydraulic chamber, which is controlled by a normally open on/off Solenoid Valve.

When the Solenoid Valve is closed, the oil in the hydraulic chamber behaves like a solid body and transmits to the intake valves the lift schedule imposed by the mechanical intake cam. When the solenoid valve is open, the hydraulic chamber and the intake valves are de-coupled; the intake valves do not follow the intake cam anymore and close under the valve spring action. The final part of the valve closing stroke is controlled by a dedicated hydraulic brake, to ensure a soft and regular landing phase in any engine operating conditions.

Through Solenoid Valve opening and closing time control, a wide range of optimum intake valve opening schedules can be easily obtained.

For maximum power, the Solenoid Valve is always closed and full valve opening is achieved following completely the mechanical cam, which was specifically designed to maximize power at high engine speed (long opening time).

For low-rpm Torque, the Solenoid Valve is opened near the end of the cam profile, leading to early intake valve closing. This eliminates unwanted backflow into the manifold and maximizes the air mass trapped in the cylinders.

In engine part load, the Solenoid Valve is opened earlier causing partial valve openings to control the trapped air mass as a function of the required torque. Alternatively the intake valves can be partially opened by closing the Solenoid Valve once the mechanical cam action has already started. In this case the air stream into the cylinder is faster and results in higher in-cylinder turbulence.

The last two actuation modes can be combined in the same intake stroke, generating a so-called "Multilift" mode, that enhances turbulence and combustion rate at very low loads.

The Multiair Technology Benefits

The Multiair Technology potential benefits for gasoline engines exploited so far can be summarized as follows: - Maximum Power is increased by up to 10% thanks to the adoption of a power-oriented mechanical cam profile

- Low-rpm Torque is improved by up to 15% through early intake valve closing strategies that maximize the air mass trapped in the cylinders.

- Elimination of pumping losses brings a 10% reduction of Fuel Consumption and CO2 emissions, both in Naturally Aspirated and Turbocharged engines with the same displacement

- Multiair Turbocharged and downsized engines can achieve up to 25% Fuel Economy improvement over conventional Naturally Aspirated engines with the same level of performance

- Optimum valve control strategies during engine warm-up and internal Exhaust Gas Recirculation, realized by reopening the intake valves during the exhaust stroke, result in emissions reduction ranging from 40% for HC / CO to 60% for NOx

- Constant upstream air pressure, atmospheric for Naturally Aspirated and higher for Turbocharged engines, together with the extremely fast air mass control, cylinder-by-cylinder and stroke-by-stroke, result in a superior dynamic engine response

Application of the Multiair Technology to FPT Engines

The first world-wide application of the Multiair technology will be the Fire 1400cc 16V Naturally Aspirated and Turbocharged engines.

The second application is a new Small Gasoline Engine (SGE - 900cc Twin-cylinder) where cylinder head design has been specifically optimized for the Multiair actuator integration. Here again, there will be both a Naturally Aspirated and a Turbocharged version. A specific Turbocharged engine version will be bi-fuel (gasoline- CNG).

Thanks to radical downsizing, the Turbocharged Small Gasoline Engine achieves Diesel-like CO2 emission levels, which are further reduced in its Natural Gas version with CO2 emissions lower than 80 g/km in many vehicle applications.

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    • 1 Second Ago
      • 6 Years Ago
      Formula cars have used pneumatically actuated valve trains for a while now. Preston Tucker suggested this feature on his car in the 40's. Too bad it has taken so long for anyone to put this into any form of production, it's like having a cam for every occasion. Now if they could get these production engines closer to adiabatic temperatures we could see some real efficiency.
        • 6 Years Ago
        On adiabatic engines/temperatures: Besides it being doubtful that his would actually be an improvement (volumetric efficiency would go down), there was one manufacturer who actually tried to make a ceramic engine in order to reduce thermal losses. I think they failed back then because the couldn't produce the ceramics in the quality needed.
        • 6 Years Ago
        F1 cars use a pneumatic spring to CLOSE each valve. There is still a camshaft to open the valves.
        F1 19,000rpm
        Nascar 9,500rpm
        • 6 Years Ago
        The Uniair system uses hydraulics.
      • 6 Years Ago

      We all want zero emission cars, but 1st : the technology is just not ready, electric cars won't be more than city cars for quite a while 2nd : electric cars are not zero emissions since more than 50% of electricity is made from coal in this country, so even if everybody was driving a full EV car it wouldn't make even a dent in the CO2 emission. Electric car will take time to ramp up as well as clean generation of electricity, we have to accept it as a fact of life, so progress on the ICE are still welcome. It is a big mistake to believe that technology only will save us, you know if you put 2 persons in a car instead of one you slash 50 of emissions, if you take your bike 1 day out 2 you slash by another 50%, if you work online or work on 4 days week instead of 5 you slash even more, all this without any expensive new technology.
      • 6 Years Ago
      Its April 9th already, so I don't know if this thread has gone cold. A lot of people here really understand the Multi Air technology. I don't, but I have a question. It's in layman's language, so there is the great risk that my question couldn't be answered by people who know the answer, even if they wanted to. Here goes.

      A few days ago the Wall Street Journal summed up Multi Air technology by saying, as I recall, that "a conventional engine flows the same amount of air thru the cylinders whether the engine is at idle, or at maximum power. Multi Air reduces the air in the cylinders when the engine requires only low power."

      Is that correct? Ignoring the great difference in volume of air flow between an engine running at 1,000 rpm and one running at 6,000 rpm, unless the engine is turbo charged or supercharged, isn't the volume of air always going to be the same? If the intake valve is shut before the downstroke of the piston is complete, a small vacume will be created in the cylinder. Is that what is happening? And the vacume doesn't actually retard the cranking power of the engine, because force that could go to propelling the car is being used instead to overcome the vacume pull of the (air) shortchanged cylinder? Maybe that resistance is small, and is vastly offset by the benefit of reduced volume of fuel that goes to the shortchanged cylinder? Less gas used in the cylinder, less power produced, but less power needed at that moment, so the system is a success? Comments anyone? A shot in the dark.
      • 6 Years Ago
      "a conventional engine flows the same amount of air thru the cylinders whether the engine is at idle, or at maximum power. Multi Air reduces the air in the cylinders when the engine requires only low power."

      It's wrong. A normal internal-combustion engine controls its power output by
      having a throttle plate which restricts the airflow. Then the fuel is added in
      proportion to the mass of air. So when it's running at full power, it's like chugging
      a glass of beer; when it's at low power, it's like sucking the beer through a narrow
      straw. And sucking beer through a narrow straw is hard work and thus wasted

      The difference in the MultiAir system (and in some other variable-valve-timing
      systems) is that the mass of air going into the cylinders is controlled by the
      valve timing and there is *no* throttle. So instead of sucking the beer through a
      straw, you take a very short gulp on each intake stroke. It's more efficient for
      all operating conditions other than full power. The danger is that whereas a
      throttle is a *very* simple mechanism to control power output, variable valve
      timing is very complex. I'm not sure how the MultiAir system can really be
      "fail-safe" - you certainly don't want it to get stuck at full-power, but then if it
      sticks at minimum-power you can't really drive the car. But it's probably true that
      using low-power solenoid valves to modulate the hydraulic pressure is more robust
      than trying to directly actuate the engine valves with high-power solenoids. On the
      other hand if you still have a camshaft then you're wasting quite a bit of power
      (and paying for quite lot of mechanical complexity) in driving the camshaft.
      • 6 Years Ago
      Zero emission has to be No 1 Priority for car manufacturing -
      if they effortlessly can improve 'them old ICEs', fine, but the lion part of development resources must be directed to more rewarding and eco-friendly concepts.
      The aim of making money is not a valid excuse for meagre development grantings,
      with the sole purpose of developing "showpieces of improvement" : 10% of ~ 30% is..
      a whopping 3% improved efficiency.

      It clearly will be a ruff and tuff transformation for the car industry, but the alternative is... none.

      Surely, it will take time - that's precisely why EVERYONE have to focus on the goal, Zero Emission, ALL the time.
      Responsibility is the key word.

      The incentive for drastic change in cars to ZERO emission and VASTLY improved fuel efficiency is NOT the personal wallet and that "gas is getting so expensive", nor that "importing oil is funding terrorists".
      It's A LOT MORE SERIOUS than that.
      " - Why didn't you listen - you had so much information? - Why couldn't you have acted more determined?" ... our chidren in 30 years could ask.

      If we elevate ourselves from the pubertal drooling over shiny sports cars we just might happen to notice that every single science report on climate change is REVISING the recent worrying reports to EVEN MORE WORRYING prospects than just half a year ago. Not to mention the ones as "old" as a year ago.
      ( And to dismiss the climate threat is indeed a tremendous Responsibility ).

      What's irresponsible is to walk down the same - wrong, Big-time wrong - path.
      It's precisely because it can't happen "tomorrow" that EVERY effort is unconditional and mandatory for ALL parts: us the people, the politicians, the industry and also investors and funding.

      I repeat my claim :
      Investments in sustainable energy production have never been more TIMELY,
      considering the financial situation around the world,
      and never more NEEDED, considering the climate situation in our world.
      OUR world.
      • 6 Years Ago
      I'm pretty sure the most common VVT is hydraulic-mechanical (like VTEC) where oil pressure pushes the cam followers over to another lobe. In those systems, the valve timing at any given RPM is inherently fixed because the hydraulic pressure at any given RPM is inherently fixed.

      This system's main advantage seems to be that it can change its operation multiple times during a single revolution of the crankshaft (more importantly camshaft). So I guess output could be tailored to what the driver is asking for.

      Still, it sounds overly complex to me and subject to wear. It sounds like a regular Fix It Again Tony situation with its dependency on solenoids.

      We will see though.
        • 6 Years Ago
        The most common form of variable valve timing is electro-hydraulic. On BMW's M54 a pulse width modulated solenoid controlled oil flow into/out of the helically splined pulley (chapstick actuator ;)
        The solenoid is still there on the standard vaned pulley design.
        The newest is direct electronic actuation of the camshaft timing. (Lexus-intake, Nissan-exhaust) No one has electronic intake & exhaust. [yet]

        This Fiat Multiair system seems like the 357Sig, a solution in search of a problem.
        This system doesn't seem as versatile as BMW's valvetronic, Nissan's VVeL, or Toyota's Valvematic.
        Variable valve timing first, then direct injection second, and then lastly camshaft switching systems. (see Audi)
        Fiat probably would of had bigger bang for the buck with direct injection.
        • 6 Years Ago
        While I don't think the Uniair system (as a part of the Multiair system) is simple, as described in the article, I do think it is the best system because it is the most capable. Not only can you vary the valve lift, but you also can vary the opening and closing times of intake and exhaust valves.
        • 5 Years Ago
        Oil leakage according to FIAT is no problem for this system. The oil from the valve actuators and solenoids is the same oil that is being used to operate the rest of the engines mechanics. It is not a closed oil volume but one that is constantly being ejected from and replenished into the solenoids/actuators. The system does that considering changing factors like engine/oil temperature, consistency and “slippage”. After each valve lift the actuator/solenoid system is replenished with “new” oil volume guaranteeing the system to deliver the desired valve lift in the following phase. According to FIAT this system is absolutely fail safe and guaranteed to work for the lifetime of an engine. All existing FIAT engines on the market are known for their superior fuel efficiency and dependability. FIAT developed MultiAir over the past 10 years and it does not appear to me they would put some kind of experiment on the market. It is too early to tell but I did not hear about any problems with the 1.4 FIRE MultiAir engine FIAT is selling on it’s European models.
        • 6 Years Ago
        You are missing it. This is a throttle-less infinitely variable approach using the hydraulic fluid as a mechanical method of controlling the extent of valve lift and timing. Don't compare it to VVT or iVVT, or whatever variable valve timing scheme other manufacturers use; compare it to using an electronic solenoid to operate each valve independently of engine rotation.
        Like the BMW 3 liter 6 that shipped with a mechanical only variable lift and timing system, there is no throttle plate to get in the way of the incoming air. This reduces the pumping losses, and allows the engine to operate more efficiently. Other VVT schemes don't do this, so that part is a big deal. But that isn't the extent of it. This goes way beyond.
        We've heard for years the idea that valve systems would go fully electronic so that they could be decoupled from fixed mechanical relationships of lift and timing, but as the press release states, there are issues with fail safe operation (lose power and it all stops) and power needs (remember 48v?).
        Since it seems fully electronically actuated valves are still stuck in the future, FIAT has come up with a way to achieve the same result (near totally independent control of valve lift and duration on a per cylinder basis) with a mechanical system that doesn't require technology that we have yet to perfect.
        Obviously the fact that this is hydraulic opens up the door for leaks and other issues down the road. I live in the US, so the name Fiat for me still evokes something small, old, and unreliable. I don't know if they still have those issues in their European products or not... but this still seems like a reasonable approach to getting independent valve control without fully electronic valves.
        The ICE is an imperfect technology, but that doesn't mean we shouldn't try to do everything we can to make it as efficient as possible.

      • 6 Years Ago
      Every step down the wrong path is a step in the wrong direction.

      Here we shurely see the underlying reason that Fiat makes no efforts to develop electric vehicles.

      The principle of making air expand by heating it IS working - we've seen that in the combustion engine for the more than hundred years.
      Yes, but is it effective, energy-wise ? No it's not. Far from.
      Is it environmentally friendly to burn the fuel ( to heat that entrapped air ) No it's not. Far from.
      The ancient principle of Internal Combustion was developed in the age of the steam engine, with the main goal of speeding up the start proccess where the steam engine had its fuel burning outside the water tank which took a long time to heat up.

      The 'heat-the-air' principle is a lousy one: after over hundred years of development the efficiency is still down way below 50% - even half of THAT is frequently seen (!).
      As seen in this example, they're STILL struggling with a lousy powerband , apart from the obvious inability to start. Not many seem to even think about the fact that
      the ICE depends on an ELECTRIC MOTOR to even start
      ( still with that lousy powerband and absolutely hidious efficiency ) . . . ( apart from the environmentally harmful exhausts ) ... ( and those abnormal financial consequences that transfer absolutely pervert amounts of money to selwct parts of our world ).

      Big Oil has been playing political power games with our worlds - yes! OUR World ! - environment and the legacy to our children for way too long now, and the purpose of car industry is certainly business - NOT the actual needs of humanity. They certainly operate in mutual understanding with the Oil empires.

      We must demand from the politicians in power to
      to a rational, clean, efficiant, economical, silent, sustainable propulsion system.

      Investments in sustainable energy production have never been more timely,
      considering the financial situation around the world,
      and enver more needed,
      considering the climate situation of OUR world.

      We HAVE to S-T-O-P burning things to get power.
        • 6 Years Ago
        EV-1, that's one long-term goal. As much as many would like it to happen tomorrow, the widespread adoption of batteries, chargers etc. will take a while. In the meantime, it would be irresponsible for automakers like Fiat to soldier on with no advancements in fuel efficiency or emissions controls.
        • 6 Years Ago
        It's more than apparent that you have no clue about combustion engines. I mean, tell e.g. MAN Diesel that combustion engines aren't more efficient than 50%. I'm pretty sure they'll have a laugh.
        • 6 Years Ago
        What a nut! Who killed the ev-1? Conspiracy!!! The politicians will save us!!

        Why do you bother to read a car sight? This is just an article on further developement of the internal combustion engine. Props to Fiat for some good engineering. Is it the future? No. It is just another step towards electical vehicles. Until they solve the battery/fuel cell issues hybrid vehicles will still require gas engines. Isn't it good if they pollute less and are more efficient?

        Moonbeam, say "hello" to Al Gore.
      • 6 Years Ago
      First let me congratulate you all this is the best thread ever, you're all right in you observations as far as I can tell. The real problem as I see it is our state of unreadiness, not just the development level of EV's, their electron storage, or the distribution and recharge infrastructure, it's the lack of doing the things we can that make the most impact - a process to reduce those sources of pollution most easily removed - dare I say the removal of all pre-1995 vehicles and to those who so dearly love their old cars a $1 per mile charge for running it (escalating by a dollar per year indefinitely every Jan 1) and providing a huge incentive to buy the lowest emitting replacement). The fantastic thing about this announcement is the prospect of an 80 gram 200hp engine that runs on CNG, with the ecvt's that are available today this combination could power most everything on the roads today.
      This could put Chrysler at the top in a stroke, and with the need to replace all the aforementioned removed vehicles (& intelligently recycled) this could reopen every factory and recall every laid off worker in the continent.
      • 6 Years Ago
      You DON'T want to remove pre-1995 cars that are fuel-efficient like the Civic.

      CNG is a joke here in the U.S., as only a handful of states have a public refueling infrastructure (most refueling stations are only for government fleet vehicles).

      The biggest hurdle remains the cost of the battery pack.

      We'll have a lot more EVs at $100/kWh than at the current $1000/kWh.
      • 6 Years Ago
      Bill, you're right if you don't have it available at home. Where it is available you could enquire with the utility if you can get home filling - a 4-stage 220V compressor unit and all the fixings to fill the tank overnight, my utility trialed this on a lease arrangement.
        • 6 Years Ago
        That home refueler is only available in a handful of states here in the U.S., and is so expensive (several thousand dollars installed) that most with CNG vehicles prefer to use a "fast-fill" commercial refueling station instead.
      • 6 Years Ago
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