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The Return of VCR: Variable Compression Ratio (VCR) technology for powertrains is back. Or at least that's what I discovered while attending this year's Geneva Motor Show.

Amidst the glamour and glitz glitz   Informal
n.
Ostentatious showiness; flashiness: "a garish barrage of show-biz glitz" Peter G. Davis.

tr.v.
 of new model launches at the 78th International Motor Show in Geneva Geneva, canton and city, Switzerland
Geneva (jənē`və), Fr. Genève, canton (1990 pop. 373,019), 109 sq mi (282 sq km), SW Switzerland, surrounding the southwest tip of the Lake of Geneva.
 show at the beginning of March, almost hidden from view, was a small company highlighting its vision of a brighter and greener future. However, it was not some unrealistic advanced technology being promoted by a starry-eyed engineer who had lost all sense of commercial reason, but what seems to be a viable solution with real-world potential.

Variable Compression Ratio Variable compression ratio is the technology to adjust internal combustion engine cylinder compression ratios on the fly. This is done to increase fuel efficiency while under varying loads. Higher loads require lower ratios to be more efficient and vice versa.  (VCR VCR: see videocassette recorder.
VCR
 in full videocassette recorder

Electromechanical device that records, stores on a videotape cassette, and plays back on a TV set recorded images and sound.
) technology is hardly new--Harry Ricardo built and tested the first such engine in the 1920s--but in recent years it has been the focus of some interest. Saab had a bash at it in 2000 with its SVC (1) (Switched Virtual Circuit) A network connection that is established at the time the transmission is required and disconnected when the session is completed.  (Saab Variable Compression) concept, as have other companies including Nissan, PSA (Professional Services Automation) An information system designed to organize, track and manage all opportunities, work, resources, costs, revenues and invoices to improve the productivity and efficiency of the workforce.  Peugeot-Citroen, Renault, and Volvo. For all the benefits that it offers in theory, though, it failed to deliver in practice and soon gave ground to direct injection.

One of the present challenges in automotive engine Automotive engine

The component of the motor vehicle that converts the chemical energy in fuel into mechanical energy for power. The automotive engine also drives the generator and various accessories, such as the air-conditioning compressor and power-steering
 technology, though, is the improvement of thermal efficiency In thermodynamics, the thermal efficiency () is a dimensionless performance measure of a thermal device such as an internal combustion engine, a boiler, or a furnace, for example.  and hence fuel economy and lower emission levels. And one of the key features affecting thermal efficiency is the compression ratio, which is always a compromise in fixed compression ratio spark ignition engines. This is why the VCR concept remains so compelling to some, including French engineer Vianney Rabhi of MCE-5 Development, the company that I spotted in Geneva. "VCR technology can achieve around 10% fuel saving when running the engine with the optimal compression ratio under all load and speed conditions," says Rabhi, "but this figure can go as high as 18% when downsizing (1) Converting mainframe and mini-based systems to client/server LANs.

(2) To reduce equipment and associated costs by switching to a less-expensive system.

(jargon) downsizing
 is taken into account while maintaining torque and performance by high boosting. Overall fuel consumption reduction of up to 27% is possible with the new technology without any disadvantages in drivability, pollutant emissions, and with only moderate production cost increase."

[ILLUSTRATION OMITTED]

He has been working on VCR engines for more than 20 years, registering several patents on the technology in the 1980s. However, the real boost came at the turn of the century with the formation of MCE-5 Development, the name reflecting Rabhi's VCR concept that he had invented in 1997, by a small group of engineers. The major impetus, though, came from the French government through a number of research agencies and the PSA Peugeot Citroen Group which joined the venture at the same time. In the eight years since then, the company has acquired 47 shareholders that include four financial companies and CERTAM, the engine research laboratory based in France. It is also supported by major French institutions for energy saving, innovation and transportation that include the PREDIT PREDIT Programme National de Recherche sur Les Transports, dans Les Réseaux de Recherche et d'Innovation Technologiques  program (the French program for energy and transportation), ADEME ADEME Agence de l’Environnement et de la Maîtrise de l’Energie (France; French Agency for Environment and Energy Management)  (the French Agency for Environment and Energy Management), ANVAR ANVAR Agence Nationale de Valorisation de la Recherche (France)  (the French Agency for Innovation), Ministry of Research and the Ministry of Industry.

Externally, the MCE-5 engine looks no different than a conventional one and it remains compatible with all combustion chamber shapes and cylinder head designs. All the components are enclosed in the engine block and no moving part is visible from the outside. Another significant factor is that it can be fixed into vehicles and connected to the gearbox, pipes and peripherals as if it were a conventional engine. The difference internally is the piston control and movement. Instead of it being located on a crank, the clever design means that the piston slides absolutely vertically on a geared rail so that piston slap is zero. However, its kinematics kinematics: see dynamics.
kinematics

Branch of physics concerned with the geometrically possible motion of a body or system of bodies, without consideration of the forces involved.
 remains exactly the same as that of a conventional engine with the same rod/crank ratio. This remains always true whatever the compression ratio which ranges from 7:1 to 18:1.

"The piston is roller-guided and is no longer subjected to rod thrust so there is no piston radial stress or piston slap," says Rabhi. "The forces that generate torque on the crankshaft are entirely assumed by the rollers--this arrangement reduces friction losses and widely extends the cylinder lifespan. This constitutes a strong response to the durability problem of highly downsized high-loaded engines." It is also the first and only intelligent VCR engine with a floating compression ratio as it features integrated hydraulic actuators that provide a wide range, precise and continuous compression ratio control for each cylinder.

The connecting rod and crankshaft have both been designed in collaboration with companies that produce several millions of them a year, says Rabhi. "The forging processes selected for these parts are those already used in the automotive industry. The cost price of each basic part that do not require specific manufacturing processes were identified, all of which has meant that it is possible to mass produce the MCE-5 engine in the near future." This latter point is often the killer for new technologies but Rabhi says that the MCE-5 engine will actually save carmakers money. "Our studies have shown that in the worst case scenario
This article is about the television show. For other uses, see worst-case scenario.


Worst Case Scenario is a reality show aired on TBS in 2002 in the U.S..
 the additional cost to producing it and the turbocharger tur·bo·charg·er  
n.
See turbosupercharger.



turbo·charged adj.
 amounts to around $750, approximately the cost price of a diesel particulate filter “DPF” redirects here. For plasma focus device, see dense plasma focus.
A diesel particulate filter, sometimes called a DPF, is a device designed to remove diesel particulate matter or soot from the exhaust gas of a diesel engine.
. However, when used to replace a large V6 gasoline engine, it generates savings of approximately $1,200 per vehicle while offering the same performance level. At equivalent or lower fuel consumption levels, a vehicle equipped with the MCE-5 engine is less expensive than a diesel and far less expensive than any hybrid, so that the cost price per kilowatt of power or per Newton meter of torque is below current standards."

While the core attribute of a VCR engine is in allowing downsizing and consequent fuel and emissions savings, the downside is that it can affect drivability. However, Rabhi is adamant that this is not the case with the MCE-5. "Drivability is not an issue because it relates to low end torque," he says. "It's necessary when you downsize Downsize

Reducing the size of a company by eliminating workers and/or divisions within the company.

Notes:
When a company downsizes, it is attempting to find ways to improve efficiency and increase profitability.

It is sometimes referred to as trimming the fat.
 an engine to have high torque at low revs without any turbo lag--and we have an extremely high torque with that of our 1.5-liter engine being better than that of a conventional 3.0-liter V6. As far as hard numbers are concerned, peak torque is around 3,500 rpm on a normally aspirated engine while we have 265 lb-ft at 1,800 rpm on the MCE-5 with most of it being available from 1,500 rpm. The price that the customer pays per mile must remain low, taking into account the price of the vehicle, its running costs and also the resale price," says Rabhi. "Good performance levels, low fuel consumption and reasonable purchase prices remain indispensable qualities for future cars, conditions that are necessary for cars of the future if cars are to contribute to lowering global [CO.sub.2] emissions and fuel consumption in a significant manner. "However, it is pointless to produce low fuel consumption vehicles that do not sell well or at all because they are too expensive. It's therefore essential to find simple, low cost solutions and this has been our strategy and our solution is the variable compression ratio."

wilkimberley@yahoo.co.uk
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Title Annotation:Euro Auto
Author:Kimberley, William
Publication:Automotive Design & Production
Date:Apr 1, 2008
Words:1158
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