Powerful and small: MCE-5 Variable Compression Ratio engine
Meet the MCE-5 VCR engine, coming at you from France. VCR stands for Variable Compression Rate, and its creators claim it will replace conventional Fixed Compression Rate engines. According to the press release (found after the jump), what is special about this engine is that it's based on a combination of rod-crank mechanism and long-life gears, integrating both power transmission and compression ratio control for each cylinder.MCE claims that this allows ratios from 7:1 to 20:1, which adapts the engine for most usage requirements. Oh, and this reduces fuel consumption by 30 percent, as two other prototypes of VCR engines showed by Saab and Audi in 2000. MCE also claims the design is more durable and robust, and will have lower maintenance costs.
This engine has no impact on the rest of the components of a vehicle, so it's potentially installable in every sort of vehicle. MCE's current prototype offers 160 kW (218 HP) with a 1.5-liter engine.
Gallery: MCE-5 VCR Engine
Press Release:
All carmakers share the same opinion: Variable Compression Ratio is the most efficient solution to reduce gasoline engines' Fuel Consumption while opening the way to several strategies for the future.
In March 2000, Saab unveiled its Variable Compression Ratio (VCR) prototype vehicle, powered by a 1.6 L supercharged VCR engine named SVC (Saab Variable Compression). The SVC engine delivers 168 kW of power (228 hp) and 305 Nm of torque, and provides more than 30% Fuel Consumption reduction when compared to a conventional naturally aspirated engine of equivalent power.
Few months later, FEV Motorentechnik also unveiled its own interpretation of Variable Compression Ratio through an impressive A6 Audi, powered by a 1.8 L VCR engine. Thanks to VCR, the FEV engine presents the same performance than that of a 3.0 L engine while reducing Fuel Consumption by 27%.
Saab and FEV demonstrated that Variable Compression Ratio is well the ultimate tool to reduce Fuel Consumption of Spark Ignition engines (gasoline engines).
But Variable Compression Ratio is not a revolution; VCR is only a major technical evolution, which could rapidly be as indispensable for SI engines as multiple Direct Injections for Diesel engines.
In the near-future, VCR will provide to automotive industry a wide range of efficient strategies to produce fuel-efficient, powerful and attractive cars which conform to most stringent emissions standards.
Then the question is: as present, environmental and energy context cannot be more suited to such a strategy, why don't carmakers already produce VCR engines?
In fact, all carmakers don't share the same opinion - for the time being - concerning the point of planning VCR engines production for the near future. Indeed, even if VCR is an old dream which goes back 100 years, producing VCR engines represents a real technological challenge which implies big changes in engine's mechanical definition.
Different VCR prototypes have confirmed the exceptional potential of VCR strategy, but they also revealed that designing VCR engines that respond to mass-production requirements is a tremendous technological challenge.
In this context, next step is to identify and study a design that fulfils all indispensable features for a mass-produced engine in terms of functionalities, robustness, reliability and durability while presenting reasonable production costs.
This is the purpose of the MCE-5 VCR engine block that is intended to replace conventional Fixed Compression Ratio engine blocks. Based on the combination between a rod-crank mechanism and long-life gears, the MCE-5 is an all-in-one VCR technology integrating both power transmission and Compression Ratio control.
Its conservative combustion chamber and its totally conventional and invariable piston kinematics allow making the most of know-how related to combustion and performance control.
The MCE-5 provides an individual, continuous and reactive Compression Ratio control to each cylinder of the engine. Its wide control range comprised between 7:1 and 20:1, permits serving all VCR strategies with no limitation.
Thanks to its long-life gears and to its roller-guided piston which is no longer subjected to radial stress and slap, the MCE-5 guarantees a high robustness and reliability to high-loaded VCR engines, and responds to one of the greatest challenge of high specific power and torque engines: durability.
The high robustness of the MCE-5 VCR engine block also comes from its rigid structure and crankshaft, which ensure a high reliability and a long lifespan to hydrodynamic bearings.
The MCE-5 VCR engine block has no impact on other engine parts or vehicle components. Its connection to gearbox, pipes and peripherals requires no additional device, as well as its integration into vehicles, which remains conventional.
The MCE-5 VCR engine bock has been studied and tested since 1997 and improved by successive steps. Next MCE-5 generation will be representative of a mass-production version and its components will be realized using industrial processes.
Thanks to its reasonable production costs and exclusive features, the MCE-5 could rapidly lead to a new generation of fuel efficient, powerful and attractive vehicles, while opening the way to crucial engine design strategies for the future.
[Source: MCE (thanks to Dominique for the tip)]
Reader Comments (Page 1 of 1)
Calvin Azzola 9:49AM (4/10/2008)
218hp from 1.5L?!? That would be quite an accomplishment. Variable compression should also be able to take advantage of the naturally higher octane rating of ethanol. Maybe that would eliminate the energy tradeoff from regular fuel.
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Gordio 10:51AM (4/10/2008)
Yea...1.5L for 218 hp is...amazing. The s2000 is 2.0L 200hp. I guess it makes sense given s2000 is a fixed ratio.
What fuel will this run on? I'm no expert, but if the compression ratio is high, and if the fuel octane level is not high enough, won't it "hiccup"? Unless that's intended. Diesels, which get good mileage, detonate by compression not by spark plugs.
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MikeW 11:13AM (4/10/2008)
Yes, but didn't VW hop up the twincharger to 220hp for racing.
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rgseidl 11:26AM (4/10/2008)
The high compression ratios are used near idling, the low ones at rated power. The former increases efficiency while the reduces the need for mixture enrichment.
I'm not sure if the 218hp number refers to a naturally aspirated version of this engine. Normally, you'd need at least one turbo stage if not two to reach that high.
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Architeuthis 12:32PM (4/10/2008)
I like the idea in principle, but ... since it is the mass flow that counts and not the volumetric displacement how is this any better than a VGT or Miller cycle? Also, the specific power looks impressive, but ... what does "1.5l" even mean? Max swept volume on the power stroke? Volume of compression stroke at minimum CR?
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steven 2:03PM (4/10/2008)
@2: The S2000 is a 2.2l with 237 HP
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Chris M 4:04PM (4/10/2008)
I'm a bit curious as to how they achieved the variable compression, sounds like some sort of modified crank mechanism.
Certain types of variable crank mechanisms could act as a true Atkinson cycle, where the power and exhaust strokes are longer than the intake and compression strokes. That allows the engine to extract more energy from the hot expanding gases.
With enough variation in compression ratios and 2 sets of fuel injectors, they could make a real "Flex Fuel" engine that could run as spark ignition, Diesel, and even HCCI!
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BlackbirdHighway 4:53PM (4/10/2008)
Chris, the gallery has some diagrams that help, even one that is animated. They also have some high res photos that are nice, but not terribly helpful in understanding it.
Steven, the original S2000 was 2L, and 240 HP. You are correct about the newer ones.
Seems like are fairly complex mechanism. I know there is less wear on the piston, but those gear teeth might have wear issues. Overall, an interesting design. Hope it really turns out to be useful.
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Kevin Nugent 12:22AM (4/11/2008)
Is it cost effective . everything looks good on paper but it comes down to actually building such a device
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Chris M 3:21AM (4/11/2008)
Thanks, Blackbird, the gallery did help. Looks like the compression ratio is regulated by a hydraulic piston next to the combustion chamber. Atkinson Cycle operation is possible, but would require sophisticated fast acting hydraulics.
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John-Christopher 3:33PM (4/11/2008)
Variable compression CAN turn a gasoline motor into a true diesel equivalent that runs on true (not pre-mixed) dual-fuel (gas + ethanol combines via separate tanks / common rail injectors to maximize power output).
The mix variability and compression variability will allow non-detonation at high loads and temperatures. As evidence of the capability, alc or even water injection, is a common practice for racers and tricked diesel trucks that can push 1200 ft-lb of torque. But at the same time the complexity of control would be astounding under ideal conditions, and offers the opportunity for secondary and even tertiary things to affect things downstream in a major way - a slight leak in one cylinder for instance throwing off a sensor in the exhaust.
This motor addresses the build issues directly, for a functionally great concept: a conventional motor that offers:
* true dual fuel capability without pre-mix (from 0 to 100% gas or alcohol),
* something like 100% power to weight improvement,
* and I think potentially something like 60% lower fuel cost overall, with (ethanol-stretching / power maximizing) variable fuel mix.
directly, and is an alternative to a non-VCR using dual turbos & supercharger.
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John-Christopher 4:22PM (4/11/2008)
Boy, I'd like to comment on the design. That is really a sweet design. It's so good IMO that I doubt that it is exactly novel here -- it probably has evolved and I'm not familiar with past efforts.
In case you don't get it -- the piston is on the left and the ugly clone on the right is fixed except for limited travel when adjusting the compression. Although the text implies independent piston adjustment -- not so much. From what I see in the exploded diagram the four adjusters are controlled by a lobed cam, and this is controlled by a single motor (sticking out on the right, about the size of a wiper motor.)
The trick is that the adjusters form the right side of a cantalever system that (x4) operates under typical hi-po conditions -- and much higher revs than a diesel.
This combination of novel build and simplicity is what makes it seem so sweet -- since the piston is rigid it seems like (I count) the same number of moving parts as in a conventional setup.
Mech-Engineering wise the weak / delicate / critical design issues seems to have to do with distribution of power across those gears and castings. Fluid dynamics (SAE type) might call for a special oil formulation to compensate for the obvious differences compared with simple rotary crank and wrist bearings. Gee -- VCR oil by the gallon -- who'da guessed?
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John-Christopher 4:48PM (4/11/2008)
Actually my wrong: there are two more critical moving parts just for the pistons: the little roller gear is radial-load bearing on its flats; and of course the incredible machine work and casting in the middle.
THEN you add the entire cam adjustment setup, which seems non-critical in terms of mechanics (except the gearbox), but seems like a lot of parts. I'll bet it can be simplified.
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Kit-Cat 11:35AM (5/08/2008)
Variable compression ratio engines as stated in the lengthened portion of the article, have a long history. Just Google "variable compression engine" in the patents search engine and you'll see.
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boomhauer 11:18PM (6/25/2008)
this design is awful. infiniti has a much better one in the works that doesnt have these giant moving gears and such. Honestly, after seeing many VCR designs this one is probably the worst. Even the big piston adjusters next to the real pistons, could be easily replaces with a much smaller cam system, again like the infiniti system. go read it: http://www.nissan-global.com/EN/TECHNOLOGY/INTRODUCTION/DETAILS/VCR/
I just hate seeing lousy tech passed off as leading edge.
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herman 6:08AM (12/22/2008)
Well boomhauer there are alot company's busy with it.
http://www.gomecsys.com Had a working 2 in line motor with 100 hp working at the dutch television.
You could hold the engine in your hand.
Anyway.. they are now busy with a 600 hp engine that can get 60 to a gallon.
There system also looks promising. But it isnt a car maker...
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paintball barrel 3:33PM (1/17/2010)
herman, (yes, very slow reply ;), that gomech system looks really bad too. there is no way that crankshaft would last more than a single revolution before blowing up, and then the extremley obvious problems of balance.. those dual sets of pistons on each crank journal would blow itself apart in minutes, if it werent for the fact that the crank already blew up. Yet another "wow looks good on paper" designs that just cant possibly work.
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