Δύο νέοι PureTech κινητήρες από τη Citroen

H Citroen θέλοντας να μειώσει τον μέσο όρο εκπομπών CO2 έως το 2020 παρουσίασε τη νέα οικογένεια PureTech τρικύλινδρων βενζινοκινητήρων οι οποίοι διαθέτουν μικρότερη κατανάλωση και λιγότερες εκπομπές CO2 κατά 25%. Κατασκευάζονται στο εργοστάσιο Tremery της Γαλλίας και θα τοποθετηθούν στο άμεσο μέλλον στα C3, DS3 και C-Elysee.

Αρχικά θα υπάρχουν δύο εκδόσεις. Μια 1.000 κ. εκ με 68 άλογα και μια 1,2 λίτρων με 82 άλογα. Αργότερα θα υπάρχουν και άλλες εκδόσεις που θα αποδίδουν 68 άλογα/λίτρο. Ο πρώτος, έχει μέση κατανάλωση 4,3 λίτρα/100 χλμ με 99 γρ/χλμ εκπομπές CO2 ενώ ο δεύτερος 4,6 λίτρα/100 χλμ με 107 γρ/χλμ εκπομπές CO2. Τα νούμερα αυτά είναι κατά 25% βελτιωμένα σε σχέση με τους κινητήρες που αντικαθιστούν, ενώ παράλληλα ζυγίζουν και 20 κιλά λιγότερο.

[Πηγή: Citroen]

[learn_more caption=”Δελτίο Τύπου”]

CITROËN TAKES A NEW STEP FORWARD IN CRÉATIVE TECHNOLOGIE WITH PURETECH ENGINES

Meeting 2020 objectives on the reduction of greenhouse gas emissions calls for the development of new technologies. Engines play a cornerstone role in these efforts. The launch of a new generation of engines is also an opportunity to introduce a number of advances that are beneficial to all, especially in terms of environmental respect, driving pleasure and lower cost in use.

The arrival of the new PureTech petrol engines in the CITROËN range is still further proof of the Brand’s “Créative Technologie”. Featuring cutting-edge technologies, the new family has equivalent or superior power compared with the previous generation combined with significantly lower fuel consumption and greenhouse gas emissions, down by roughly 25%. Available on several Brand ranges (CITROËN C3, DS3 and C-Elysée), the new engine family is produced at the Trémery site in France.

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 pollutant emissions and fuel consumption, and also to reduce the weight of the powerplant and make it more compact. The specifications also stipulated a specific power of 50 kW per litre. Several capacities were developed, of which two are available today: a 1 litre and 1.2 litre with power ranging from 68 bhp to 82 bhp EEC (50 to 60 kW). Depending on the model and the tyres fitted, combined cycle fuel consumption for the new family is between 4.3 and 4.6 l/100 km and CO2 emissions range from 99 to 107 g/km, for an approximate 25% reduction on the previous generation of engines.

PERFORMANCES PERFECTLY IN LINE WITH NEEDS

Two PureTech engines are already available:

• PureTech VTi 68: fuel consumption reduced by 1.6 litres per 100 km
• The VTi 68 engine, available on the C3, has a capacity of 999 cm3.
• Maximum power of 50 kW at 6,000 rpm is up 6 kW (10 bhp) on the 1.1 litre engine it replaces.
• Progress has been made across the board, with top speed up 8 km/h and 0 to 100 km/h a full
• 2.3 seconds faster. Combined-cycle fuel consumption is down 27% or 1.6 l/100 km to 4.3
• l/100 km, while CO2 emissions are a full 38 g/km lower at 99 g/km.
• PureTech VTi 82: economy plus top-level performance
• The VTi 82 engine, available on the C3 and DS3, has a capacity of 1,199 cm3.

Maximum power of 60 kW comes at 5,750 rpm, for a 6 kW (9 bhp) increase on the 1.4 litre unit it replaces. Impressive advances have also been made with this version. Top speed is up 11 km/h and the 0 to 100 km/h dash is 1.9 seconds faster, while fuel consumption is down 1.5 l/100 km (or 25%) on the previous generation to 4.5 l/100 km and CO2 emissions are 35 g/km lower, at 104 g/km.

An additional version with the same capacity, the VTi 72, is already available on the new C-Elysée.

TECHNICAL CHARACTERISTICS FEATURING THE FINEST TECHNOLOGY

The PureTech engine family features the latest technologies to meet user expectations as closely as possible:

· A timing system with two overhead camshafts controlling 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, for better performance at low and medium engine speeds and optimised fuel consumption,

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

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

A NEW APPROACH TO MEET AMBITIOUS OBJECTIVES

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

· Downsizing (reduction in capacity)

· The choice of three cylinders rather than four

· Reduced weight and more compact design

· Reduced internal friction

· Optimised combustion.

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. Downsizing with improved efficiency
Besides reducing weight and friction, downsizing technology serves to significantly reduce fuel consumption and CO2 emissions. Already used on a number of other Brand engines, diesel and petrol included, downsizing is particularly relevant for the new engine range, which is now the entrylevel offer.

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 rather than four cylinders for multiple gains A three-cylinder engine has a number of advantages over a four-cylinder one, including reduced energy loss through friction, fewer moving parts, lower weight and more compact dimensions, all of which cut fuel consumption.

Lighter and more compact

By reducing the number of cylinders, as well as redesigning several components, the weight loss compared with the previous engines is 25 kg for the VTi 68 and 21 kg for the VTi 82, or over 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 co-design 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 100 mm in width and 70 mm in height, accessories included. Significant reduction in friction and the number of moving parts

The decisions made during the design phase of the PureTech engine family led to developments on a number of major parts aimed at reducing engine friction loss, 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 piston jackets, off-centred. The piston pins, segments and push rods in the timing system feature a low-friction coating (in diamondlike carbon) to keep friction down to a minimum.

The regulated, variable-capacity oil pump continually provides optimal lubrication pressure. Friction linked to this part has been reduced by 30%. 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. Optimised combustion for maximum reduction of fuel consumption and emissions The combustion system, a crucial component in fuel consumption and emissions, takes full advantage of the engine technologies. The bore/stroke ratio was chosen to optimise 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 optimised to enable the combustion system to work with high rates of Internal Gas Recirculation, which reduce 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 optimise 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.

[/learn_more]