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Citroën introduces first members of new 3-cylinder gasoline engine family; 1.0L and 1.2L PureTech reduce fuel consumption about 25%

11 December 2012

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PureTech 3-cylinder engine. Click to enlarge.

Citroën is introducing the first members of its new PureTech family of three-cylinder gasoline engines on the C3, DS3 and C-Elysée (for international markets) ranges. The PureTech engines offer equivalent or better power compared with the previous generation powerplants, combined with significantly lower fuel consumption and greenhouse gas emissions, down by roughly 25%.

Citroën developed two different capacity versions: 1.0-liter and 1.2 liter with power ranging from 68 hp to 82 hp (50 to 60 kW). Depending on the model and the tires fitted, combined cycle fuel consumption for the new family is between 4.3 and 4.6 l/100 km (51.1 to 54.7 mpg US) and CO2 emissions range from 99 to 107 g/km.

The design brief for the new-generation PureTech engines called for a clean break in powertrain development. The objective was to make substantial cuts in emissions and fuel consumption, and also to reduce the weight of the engines and to make them more compact. The specifications also stipulated a specific power of 50 kW per liter.

To achieve these results, PureTech development called for a number of changes, chief among which were:

  • Downsizing. To deliver at least the same performance as the previous generation, engine efficiency had to be improved to offset the reduction in the number of cylinders.

  • Three cylinders. A three-cylinder engine has a number of advantages over a four-cylinder powerplant, including reduced energy loss through friction, fewer moving parts, lower weight and more compact dimensions, all of which cut fuel consumption.

  • Reduced weight and more compact design. By reducing the number of cylinders, as well as redesigning several components, the weight loss compared with the previous engines is 25kg for the VTi 68 and 21 kg for the VTi 82, or more than 20% for assembled engines without accessories (alternators, starters, etc.).

    Using a special casting technique called investment casting, the cylinder heads, in lightweight alloy, feature a number of functions that limit weight and dimensions. The exhaust manifold is integrated directly in the cylinder head, which reduces the number of parts and overall weight. The cooling system outlet module and the upper engine support, both integrated, also figure among the parts that come directly out of casting at the Charleville foundry.

    The cylinder casing, again in lightweight alloy, combined with work right from the start of the project by the design, casting and machining teams, as well as the use of digital technology in mechanics, thermomechanics and acoustics, also led to weight reduction and the integration of a number of functions. Made from pressure-cast aluminium, the cylinder casing features linings that are inserted during casting at the Mulhouse foundry.

    The engine is also much more compact than the previous generation, having lost 100mm in width and 70mm in height, accessories included.

  • Reduced internal friction. The decisions made during the design phase of the PureTech engine family led to developments on a number of major parts aimed at reducing friction, which accounts for roughly 20% of the power consumed by an engine.

    The main parts and components concerned were the crankshaft—and specifically its sizing—and the off-centered piston jackets. The piston pins, segments and push rods in the timing system feature a low-friction coating (in diamond-like carbon) to keep friction down to a minimum. The regulated, variable-capacity oil pump continually provides optimal lubrication pressure.

    The timing belt, wet and housed in a casing, has the same lifespan as the car itself. This technology also helps to reduce engine noise. All these improvements make the PureTech engine the new benchmark on ultra-low friction, which has been reduced by 30% overall.

  • Optimized combustion. The bore/stroke ratio was chosen to optimize the compromise between the intrinsic efficiency of the combustion system and engine friction loss.

    The internal aerodynamics (intake ports, shape of piston heads and combustion chamber with an 11-to-1 compression ratio) were optimized to enable the combustion system to work with high rates of Internal Gas Recirculation, which reduces fuel consumption and pollutant gas emissions.

    To get the engine up to temperature faster, the engine uses Split Cooling technology. When the car starts up, with the engine cold, the cooling circuits in the cylinder block and head are separated to optimize the warm-up process. This system has two advantages. One, it reduces CO2 emissions, which are higher when the engine is cold. And two, it helps to warm up the cabin faster.

    For maximum efficiency, the three-way catalytic converter is located right at the engine outlet and equipped with two lambda sensors.

Some 52 patents were filed in the development of the new engine family, 23 concerning engine architecture, 20 engine control and 9 special manufacturing processes and tools.

The VTi 82 engine, applied in the C3 and DS3, has a capacity of 1,199cc. Maximum power of 60 kW comes at 5,750 rpm for a 6 kW increase on the 1.4 liter unit it replaces. Top speed is up 7 mph (11 km/h), and fuel economy is also improved by up to 1.5 l/100km—25% compared to the previous generation engine—to 4.5 l/100km (52.3 mpg US). CO2 emissions are up to 35g/km lower at 104 g/km.

The VTi 68 engine, which will be available in the C3 range next year, has a capacity of 999cc. Maximum power of 50 kW at 6,000 rpm is up by 6 kW compared to the 1.1 liter engine it will replace. Progress has been made across the board, with the top speed increasing by 5 mph (8 km/h). Combined-cycle fuel consumption is down 1.6 l/100km to 4.3 l/100km (54.7 mpg US), while CO2 emissions are a full 38 g/km lower at 99 g/km.

The PureTech engine family features a timing system with two overhead camshafts and four valves per cylinder, controlled directly by two mechanical push rods for enhanced fill-up and efficiency. Continuous variable hydraulic timing for the intake and exhaust camshafts enable better performance at low and medium engine speeds and optimized fuel consumption.

On the VTi 82 version, a counter-rotating balancer shaft provides reduced vibration and quieter operation.

Electronic management optimizes battery charge, with freewheel alternator operation used to a maximum when it requires no energy expenditure.

The new engine family is produced at the Trémery site in France.

December 11, 2012 in Engines | Permalink | Comments (16) | TrackBack (0)

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Comments

Very impressive for gasoline engines - 99 - 107 gms/Km is very good for a non-hybrid gasoline engine.

Hopefully, they won't cost too much and won't be too noisy.

It is great to see what determined engineering and the EU's 130 gms (or is it 120 gms) mandate can achieve.

These engines are like accusatory fingers pointing at the builders of hybrids:  "See these?  This is what belongs under the hood of the Prius, Volt and Insight!"

It's good to see that French automakers are finally getting over their obsession with diesels.

I wonder if they will turbocharge these engines so that they can power larger cars.

@Bernard
"...Obsession with diesels." Why not? Diesel versions of these engines would have even lower fuel consumption and CO2. It is nothing new either, the VW Lupo and Audi A2 had a fuel consumption of 3 l/100 km. However, the new much larger VW Golf BlueMotion gives 3,2 l/100 km, so we could extrapolate the trend for a small 3-cylinder engine in a smaller car to substantially below 3 l/100 km with known diesel technology. Maybe it is an obsession with gasoline if they cannot recognize the advantages of diesel technology. The fact is that it is only an economic issue. Gasoline engines are cheaper.

Ford has already shown what you can do with turbocharging on a 1-liter 3-cylinder gasoline engine. This engine will shortly be used in such a large car as the Mondeo.

Yes E-P....and light weight Diesel (1.0L 3 cyls) version could do even better with regards to fuel consumption? Would it be too noisy on long rides? Would it be annoying to hear the Diesel running at 2200 rpm (or so) at each street stop light?

Why stop at three when two cylinders would be even better and be even smaller? Also, the engine would be naturally balanced; Hey Briggs and Stratton get better than 24 hp out of their air cooled models lawn tractors. Put this baby on a light aluminum chassis, install a large loud horn and you have a great Paris city car.

You mean like the Fiat TwinAir?

what i dont understand is why isnt there a motor like this paired with super caps for acceletation to get good acceleration and good gas mileage. use a hook to the Trans for the electric assist at lower rpms.

@Chicago,
Cost, I imagine. These are small engines for inexpensive cars. They can't support hybridisation, or diesel, and with this level of economy, you probably don't need it.

Once you are at 50 mpg (US), you can leave it for a while and wait for the rest of the world to catch up. (or oil to go to $200 / barrel).

@HarveyD
There are a couple of issues regarding noise and harshness for all type of 3-cylinder engine, regardless if they are fuelled with gasoline or diesel. However, now we have the technical solutions (e.g. the pendulum flywheel) to handle this. One good example is the Ford 1-liter (gasoline) engine, although it does not even use all the available technology, e.g. balance shafts. In the latest issue of Engine Technology International, you can read about the new BMW 3-cylinder engines in gasoline and diesel versions. I am sure they will meet all your comfort criteria.

To your questions: Diesels are quieter than gasoline engines on highway, so it would be quieter for long rides. My current diesel car is much less noisy than my previous gasoline car on the highway. The idle speed of modern diesel engines is not 2200 r/min; it is 800 r/min on my engine. It has never ever been as high as you suggest. All modern diesel engines have start/stop, so you would not hear anything but the fan and the radio at each stop light. You can also make a diesel engine very quiet at idle, although this does not really apply to all engines for the moment.

@Peter XX,

There's been a backlash against diesels in France. See here for example:
http://www.leftlanenews.com/french-politicians-aim-to-ban-diesels-from-big-cities.html

There's also talk of ending diesel subsidies (lower taxes relative to gasoline). This development, combined with the availability of inexpensive and efficient gasoline motors, will change the economics of running a diesel car in France. It's good to see that Citroën (PSA) isn't too far behind the curve.

Peter...sorry...the 2200 rpm mentioned was to keep the batteries charged (using a smaller ICE and generator) ...not the 500 rpm idling speed. A smaller genset would have to be used at relatively higher speed most of the time to keep the battery pack correctly charged under normal to heavy used. I mentioned 2200 rpm because it is close the the 'sweet spot' for many new Diesel.

@Bernard
Diesel share goes up and down depending on what the politicians do regarding taxation and incentives. However, the opinion of one single politician that is not informed about the latest technology will not change anything. What he proposes will not happen. The WHO study is based on very old results, tracing back to locomotive engines first introduced in 1938. It has absolutely nothing to do with modern diesel cars. In fact, if you want to reduce emissions of particles, modern cars with DPF have lower particle emissions than ambient air – they are cleaning the air. Modern gasoline cars with direct injection have 10 times higher particle emissions. Do you want to promote them?

Talking about incentives, these normally have the objective to promote a technology that is more efficient (or has lower CO2), has lower emissions and so on. Of course, anti-incentives will also work. If you want to increase energy use and CO2, you could provide incentives to gas-guzzling gasoline cars.

EP,

"These engines are like accusatory fingers pointing at the builders of hybrids: "See these? This is what belongs under the hood of the Prius, Volt and Insight!""

Yes, forty years ago. It is only the threat of EVs that has these muscle car morons now trying to prevent their own demise.

The accusatory finger points at them and says: "Why don't you care about anything but money"?

Oh, that's easy, BK4.  They only care about money because companies that don't tend not to remain in business.

What they could do instead is to stop trying to block policy changes which would better align the money-making opportunities with what's good for the public and the country.

Looming EVs and new CAFE standards.

Thanks, PBO....

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