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Fiat 875cc TwinAir named International Engine of the Year 2011

Cutaway of the 875cc TwinAir. Click to enlarge.

Fiat’s 875cc TwinAir engine (earlier post) was named the International Engine of the Year 2011. Judged by a panel of 76 motoring journalists from 36 countries as disparate as the USA, Japan, China, Russia, New Zealand, India, Korea, Germany, France, Romania, South Africa, Mexico and the UK, the Awards highlight and acknowledge engine engineering excellence.

The top award for the two-cylinder turbo was Fiat’s first, and only the second time a sub-1-liter engine took the top prize (the first being Toyota’s 1-liter Yaris VVT-i engine in 1999. The TwinAir was also named Best New Engine of the Year, Green Engine of the Year, and Sub 1-Liter engine.

Applied in the Fiat 500, the gasoline-fueled, 85 hp (63 kW), turbo two-cylinder features a small-sized turbine which, combined with dedicated valve management strategies, minimizes transient response times and keeps maximum power levels high. Compared with a 1.2-liter 8v engine, the new 85 HP turbo has 23% more power and a 30% better performance index. The performance of the two-cylinder is not only equivalent to a 1.4-liter 16v engine, but fuel consumption is 30% lower.

The TwinAir is equipped a number of features usually found in higher engine classes, such as the electrohydraulic control of the Multiair inlet valves and an innovative timing chain that cuts engine running costs because it does not need any maintenance. A counterrotating balancer shaft also guarantees that vibrational comfort is maintained in all operating conditions.

TwinAir weighs 85kg; emits 95g/km of CO2 and delivers fuel consumption of around 4.34 litres/100km (54 mpg US) in the Fiat 500.

Soon to be available in the new Lancia Ypsilon, the TwinAir will shortly also be launched on the market in the 65 HP aspirated version and in another high-performance 105 HP Turbo version, with a category-topping 120 hp/liter specific power, as well as in the ecological 80 HP Turbo bi-fuel version.

The other winners in this year’s International Engine of the Year awards were:

Best Performance Engine Ferrari 4.5-Liter V8
1-Liter to 1.4-Liter Volkswagen 1.4-Liter TSI Twincharger
1.4-Liter to 1.8-Liter BMW 1.6-Liter Turbo
1.8-Liter to 2-Liter BMW 2-Liter Twin-Turbo Diesel
2-Liter to 2.5-Liter Audi 2.5-Liter Turbo
2.5-Liter to 3-Liter BMW 3-Liter DI Twin-Turbo
3-Liter to 4-Liter BMW 4-Liter V8
Above 4-Liter Ferrari 4.5-Liter V8

In 2010, Fiat’s 1.4 MultiAir Turbo engine was awarded the Best New Engine 2010 award.

The Awards are organized by Engine Technology International, published by UKIP Media & Events, which also publishes a number of other automotive titles.



With the domination by BMW, the author could have used another headline this time...


There are 2 reasons for this:
1. The Fiat engine was the overall winner
2. This site is called Green Car Congress


I have heard that the real world economy is well off the claimed economy - we'll have to see more reviews.

The range of twin air engines looks good for the future.

However, it does not look like a good candidate for a range extender in terms of volume - it is designed to replace larger engines in a F500 engine bay, and is rather ungainly for a compact range extender.


And 2 reasons against:
1. Four titles are more than one
2. Green? A BMW 320d EDE with the sister engine of the 1.8-2.0 liter class gives you a fuel consumption of 4.1 l/100 km (4.34 l for Fiat 500). Put this engine in a Fiat 500 size of car and it will be even greener. More fun to drive, as well...


An improved (smaller?) version could become a strong candidate for a clean running, efficient, range extender.


delivers fuel consumption of around 4.34 litres/100km (54 mpg US) in the Fiat 500

The Ford Fusion hybrid gets 41 mpg city. In the U.S. buyers may want a bit more room than the Fiat can offer.


From the article: "... and only the second time a sub-1-liter engine took the top prize.."

Didn't someone conveniently forget Honda's 995 cc IMA engine in 1st gen. Insight? It was International Engine of the Year for 2000.



diesel ≠ gasoline


Put this engine in a Fiat 500 size of car and it will tip over.

Stan Peterson

I suspect it will eventually arrive in the US as part of a Chrysler-Fiat EREV.


BMW ≠ Fiat. BMW 320 is bigger than Fiat 500. 2 liter is bigger than sub-1 liter. I you take into account that you need less crude oil to produce diesel fuel, the BWW is better.

Put the Fiat engine in a 3-series BMW and you will get nowhere. With little mathematics you could envision the use 2 of cylinders from a 4 cylinder engine.

Nikolay Meshterov

Good to see so many technologies, but still the Prius is unbeatable in terms of low emissions.
Here are some numbers measured in NEDC, including the BMW 320d ED:

fiat 500 - 95 g/km CO2, 419 mg/km CO, 34 g/km NOx, 0 g/km Particulates
BMW 320d ED - 109 g/km CO2, 330 mg/km CO, 141 g/km NOx, 0.4 g/km Particulates.
prius - 89 g/km CO2, 258 mg/km CO, 6 g/km NOx, 0 g/km Particulates

The diesel is simply nowhere as green as the hybrid and the small gas engine.

@Peter XX "I you take into account that you need less crude oil to produce diesel fuel"
No idea where you get that info, but a litter of diesel definately needs more crude oil to produce since it has higher hydrocarbon content than a litter of gas.


Modern Diesel cars have particle filters. PM of 0.4 g/km is totally wrong! You should have realized that. The EU limit is 0.005 g/km. Normally, the level is a factor of 10 lower. >95% of that PM is volatiles, not solid particles. Pretty clean! Gasoline cars do not have zero PM emissions.

The efficiency of gasoline production is ~83%, diesel is ~88%. See for example MIT or NREL. Where do you get your data? Taking this into account, the BMW is ~5% better. Furthermore, how do you take car size into account? The Fiat is not big enough for USA but the BMW might be accepted.


I plan on sticking with 5+ liter V-8 engines the rest of my life thank you very much. I need big vehicles with "road presence", like my Quad Cab Dodge Ram 4 X 4. Yeah, it's got a hemi!


Fiat 500 11.000 Euro
BMW 320D ~35.000 Euro

this Fiat 500 is a nice car and driven in the right way not bad (not like a ford or opel corsa ...)

just forget BMW, far to costly, only the 6er and 5er have a nice design, but too costly ... why to spend so much money for a car :))


Fiat vs. BMW?
Let me summarize: The BMW engine has double size, double power and lower fuel consumption in a much bigger car. Fiat gets the Engine of the year victory. To be honest, I am very impressed by this little engine but I am probably the only person on this site who is more impressed by the BMW engine. Common sense: if people like the Fiat better, Fiat will sell more cars. However, I am afraid that Fiat 500 is too small for big Americans...


An excellent point Peter....if the current trend continues, there will be more and more obese drivers/passengers in North America. Already, many 9-10 year children do not fit well into a standard 22-inch seat. Eventually, one 40+/-inch front seat may be required for the driver and one 40+/-inch back seat for the occasional passenger (mate). Three rows will be required to accommodate a family with one teen age child or two very young children.

However, with future ultra light weight materials, car cabs could be enlarged without increasing the total weight of the vehicle and we could keep on eating more and more junk foods.

Some 55% to 60% of us could still fit into a Fiat 500. That is a large but diminishing market.


For my 179 cm and 69 kg body the Fiat would be O.K. but my much taller 18-year 71-kg son would not be comfortable in the back seat, simply because he is too tall...

Probably Fiat will increase the power in the future and put the engine in larger cars… maybe also increase the number of cylinders to 3. In a reasonable light medium-sized car, a 3-cylinder engine would provide sufficient power for highway driving.

Nikolay Meshterov

Peter XX,

"PM of 0.4 g/km is totally wrong! "

Applogies for the wrong units - all the CO, NOx and Particulates numbers in my post above are in mg/km.
Still, the diesel emits significantly more NOx and PM, especially when compared to the Prius which should have been the real award winner.

">95% of that PM is volatiles, not solid particles. Pretty clean!"

Care to share some sources to backup these statements? To my knowledge the volatile stuff is more dangerous, since it penetrates even deeper in human lungs.

"The efficiency of gasoline production is ~83%, diesel is ~88%."

Again, sources of these numbers? Are you sure it is about low-sulfur diesel?
According to the Diesel Dilemma report: "a gallon of low-sulfur diesel fuel requires 25 percent more oil than a gallon of low-sulfur reformulated gasoline"

link: http://www.ucsusa.org/clean_vehicles/technologies_and_fuels/gasoline_and_diesel/the-diesel-dilemma-diesels.html


Well, you show a certain lack of knowledge, so perhaps it is time for a free lesson.

It should be accepted knowledge now that smaller particles pose a greater health hazard than larger particles. EU made the choice to regulate solid particles due to health effects. These small particles are regulated for diesel cars via a limit for particle number (PN) emissions. There is yet no such limit for gasoline cars. Proposed gasoline PN limits in EU and California are ~10 times higher than for diesel cars. Are gasoline particles green? Just because these emissions are not measured and regulated it should not indicate that they are zero. Sources for data on PN & PM emissions: well, look at the European PMP program, which was the background for EU Euro 5 and 6 regulations.

If you read my comments carefully, I already gave you the sources for fuel production. MIT, ANL and NREL are well-known in the US (University and federal labs). There are too many publications to list here, so you simply have to search yourself. Of course it is low-sulfur fuel. The Internet site you referred to is rubbish. Common sense should tell you that 25% more oil cannot be realistic for sulfur removal. I prefer scientific publications, such as, e.g. those from MIT and ANL.

Nikolay Meshterov

Peter XX,

thanks for the lesson, but you seem to miss few points.
First, since no one measures PN emissions of gas vehicle how do you know they emit more than diesel vehicles which you seem to imply? And how about in case of a hybrid Prius which ICE runs at much "cooler" 8:1 compression ratio?
Second, what happens to diesel PM in a diesel vehicle with a particle filter (just like the BMW 320d ED)? Are they annihilated? No, they are stored in the filter. And what happens when the filter is full? It is regenerated by burning PM thus reducing it into... smaller PM. Yep, the much more dangerous ones. This process is not reflected in any of the vehicle emission certifation procedures.

As for diesel/gas crude oil content - you do realize that diesel contains an average of 13.5% more hydrocarbons than gas per unit volume, right? Which, assuming 100% efficiency of crude oil to gas or diesel conversion, translates into 13.5% higher crude oil content, i.e. a certain volume of crude oil is converted into either 1 volume unit of gas or 0.88 volume units of diesel.
Now, if we include the conversion efficiencies that you cite, for the same volume of crude oil we get:
gas -> 1*0.83 = 0.83
diesel -> 0.88*0.88 = 0.77
And if we take the conversion efficiencies from the following ANL publication
of 85.5% for 5-30 ppm S gas (fig A1(d))
and 87% for 5-30 ppm S diesel (fig A1(f)), we get:
gas -> 1*0.85.5 = 0.855
diesel -> 0.88*0.87 = 0.766
Sorry, but it seems diesel still needs about 10% more crude oil to produce.


@ Nikolay,

There have actually been many studies of gasoline PM emissions conducted over the past 10 years or so.

The first was a study by the Swedish National Road Administration (Färnlund et al., "Emissions of Ultrafine Particles from Different Types of Light Duty Vehicles.") which showed that gasoline engines emitted PN that approached those of uncontrolled diesel engines under many common driving conditions (high speed/load, cold ambient temperatures). This study also showed that diesel engines with DPF have the lowest PN emissions of any technology studied.

David Kittleson of the University of Minnesota also conducted a series of studies which have shown that gasoline engines emit PN that approach and in some cases exceed those of uncontrolled diesel engines under common operating conditions (David Kittelson, et al, Gasoline Vehicle Exhaust Particle Sampling Study [http://www.osti.gov/bridge/servlets/purl/829821-SQYKH6/native/829821.pdf]; D. B. Kittelson, W. F. Watts and J. P. Johnson, "Nanoparticle emissions on Minnesota highways." Atmospheric Environment, Volume 38, Issue 1, January 2004, Pages 9-19; D.B. Kittelson, W.F. Watts, J.P. Johnson, J.J. Schauer, and D.R. Lawson, "On-road and laboratory evaluation of combustion aerosols—Part 2: Summary of spark ignition engine results." Journal of Aerosol Science, Volume 37, Issue 8, August 2006, Pages 931-949).

The USEPA also funded a study in Kansas City in which it concluded that it had been significantly underestimating PM emissions from gasoline vehicles ("Analysis of Particulate Matter Emissions from Light-Duty Gasoline Vehicles in Kansas City.") Granted, that was mostly based on the fact that older gassers produced significantly higher PM emissions than newer ones, but today's new vehicles become tomorrow's old high-emitters.

A 2009 study by Ecotraffic (Sweden) showed that gasoline engine particles were almost exclusively in the nanoparticle size range (<50 nm; "Particle and NOx Emissions From Automotive Diesel and Petrol Engines.")

There are only a few studies which showed PN emissions during DPF regeneration, and those showed that they were elevated only to what gasoline engines typically emit (Karlsson, “Measurement of Emissions from Four Diesel Fuelled Passenger Cars Meeting Euro 4 Emission Standards.” AVL, 2005; CARB, CALIFORNIA’S INFORMAL PARTICIPATION IN THE PARTICLE MEASUREMENT PROGRAMME (PMP) LIGHT DUTY INTER-LABORATORY CORRELATION EXERCISE (ILCE_LD), FINAL RESEARCH REPORT, October 2008). By the way, in the CARB report, it was specifically mentioned that except during regeneration, PN emissions from a DPF-equipped diesel vehicle were indistinguishable from background, which in this case was HEPA-filtered dilution tunnel air.

You also neglected to mention the higher HC emissions in the NEDC of the Prius (vs. the 320d ED). The higher HC emissions in the exhaust and VOC emissions from the fuel handling would likely produce secondary particle formation in the form of SOA that would exceed those of the very low PM exhaust emissions from the 320d.


Thank you Carl!
This clarifies so many of the PM issues that I do not have comment much further on that. We can conclude that in the 2015/2016 timeframe we might have PN emission limits for gasoline cars. If we allow gasoline cars to have 10 times higher PN emissions than diesel cars; does this make gasoline cars cleaner than diesel cars? I do not think so!

It is pathetic to see that you mix density and efficiency in your calculations. The more you write, the more obvious it becomes to me that you have no clue about what you are doing. Efficiency data refer to the energy used in production and the energy content of the fuel. If efficiency of diesel production is higher than for gasoline production it means that one unit of energy in crude oil gives you more energy as diesel fuel compared to gasoline. You must understand this fundamental as a starting point. One should not mix in density in the efficiency calculation. Apparently, this is the first time you try to do anything like this. Of course I take fuel density and energy content per liter into account in my calculations. Energy content and density of gasoline and diesel vary somewhat between countries. I used energy contents of 32.8 MJ/liter for gasoline and 35.1 MJ/liter for diesel fuel in my calculations. The calculation becomes: 35.1/32.8*0.83/0.88*4.1=4.15. This is kind of “gasoline equivalent” fuel consumption of the BMW and, as you can see, it is 4.15 l/100 km. Consequently, the BMW is ~5% better than the Fiat. Other numeric values might change the calculation somewhat. However, I have to say: sorry, your error in the calculation does not imply that diesel needs 10% more crude oil to produce.


If one were to purchase a gasoline Fiat instead of diesel BMW one could easily replace appliances with efficient appliances and improve house insulation or install a solar hot water or even a photovoltaic system and drastically reduce CO2 emissions for the same €/$ spent and on top of that: Reduce the electricity and heating bills.

Besides that a diesel engine is more costly and heavier than a gasoline engine - if everybody started to produce and use diesel engines only, there would be a serious fuel supply problem.


Not everybody needs a 3 or 4 tonnes car. Many can fit in much smaller vehicles. We should continue to have the choice to match the car with our body weight/size. One tonne vehicles such be enough for the majoriy.

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