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Infiniti introducing production-ready variable compression ratio engine at Paris Motor Show

Infiniti will introduce a production-ready variable compression ratio engine VC-T (Variable Compression-Turbocharged) at the 2016 Paris Motor Show (Mondial de l’Automobile) in September. Infiniti said that the new four-cylinder turbocharged gasoline VC-T engine has been in development for more than 20 years. (Nissan was awarded a patent in 1995 on compression ratio control for an engine.)

Interest in variable compression engines stretches back more than 40 years. In a 1976 SAE paper, Grundy et al. described the Teledyne Continental Motors (TCM) AVCR 1360-2 variable compression ratio (VCR) diesel engine, the culmination of fifteen years of VCR piston and high specific output research. Two main types of variable compression ratio systems have been proposed over the years: continuous and two-stage.

There have been a number of concepts proposed to enable such VCR systems. Broadly, they can be characterized into three groups: unconventional cranktrains; systems that vary the distance between the crankshaft and the cylinder head; and variable kinematic lengths. (Earlier post.)

Infiniti’s VC-T engine technology seamlessly raises or lowers the height the pistons reach. As a consequence, the displacement of the engine changes and the compression ratio can vary anywhere between 8:1 (for high performance) and 14:1 (for high efficiency). The engine control logic automatically applies the optimum ratio, depending on what the driving situation demands.

A series of earlier SAE papers published by Nissan engineers laid out the core approach of a new piston-crank system incorporating a multiple-link mechanism to vary the piston’s motion at top dead center and thereby obtain the optimum compression ratio matching the operating conditions.

Conceptual configuration of an engine featuring the Nissan multi-link VCR technology. The piston and crankshaft are connected by means of the upper and lower links. The lower link is also connected, via the control link, to the center of the eccentric journal of the control shaft.
Rotation of the crankshaft causes the lower link to revolve around the center of the main crankshaft journal and to pivot around the center of the crankpin. The motions of the lower link are constrained by the control link. As a result of the revolving and pivoting motions of the lower link, the connection point of the lower and upper links traces a vertically long oval shape as the piston undergoes reciprocal motion.
When the compression ratio is varied, an actuator changes the angle of the control shaft relative to the engine, which moves the central position of the eccentric journal. Moving the center of the eccentric journal upward tilts the lower link clockwise, thereby shifting the top dead center (TDC) and bottom dead center (BDC) positions of the piston downward simultaneously to lower the compression ratio. Conversely, moving the center of the eccentric journal downward raises the compression ratio. Hiyoshi et al. (2006) Click to enlarge.

Other attempts to to achieve variable compression ratio with this type of method ran into difficulties from issues such as an increase in the engine size, weight increases, increased engine block vibration due to a worsening of piston acceleration characteristics and increased friction resulting from a larger number of sliding parts.

Nissan, in a 2003 paper, said that its multi-link geometry resolved those previous issues.

This multiple-link variable compression ratio (VCR) mechanism can be installed without increasing the engine size or weight substantially by selecting a suitable type of link mechanism and optimizing the detailed specifications.

The piston stroke achieved with this multiple-link mechanism resembles simple harmonic motion, unlike that of conventional engines. This motion is characterized by slower piston speed near top dead center and faster piston speed near bottom dead center.

In a 2006 paper, the engineering team applied the multiple-link VCR mechanism to a turbocharged engine to investigate its effect on engine performance. In that study, they found that fuel economy and power output can both be improved by increasing the compression ratio and applying exhaust gas recirculation (EGR) under low loads and by lowering the compression ratio and applying higher boost pressure under high loads.

(In 2008, a team from Renault and Nissan published a study on the application of the use of this VCR technology for HCCI combustion in a diesel engine.)


VC-T technology is a step change for Infiniti. It is a revolutionary next-step in optimizing the efficiency of the internal combustion engine. This technological breakthrough delivers the power of a high-performance 2.0-liter turbo gasoline engine with a high level of efficiency at the same time.

—Roland Krueger, president of Infiniti Motor Company

VC-T technology delivers multiple customer benefits including significantly reduced fuel consumption and emissions, greatly reduced noise and vibration levels; it is also lighter and more compact than comparable conventional engines.

Infiniti will present more information on the VC-T engine at Mondial de l’Automobile on September 29 during its press conference.


  • Gérard, D., Besson, M., Hardy, J., Croguennec, S. et al. (2008) “HCCI Combustion on a Diesel VCR Engine,” SAE Technical Paper 2008-01-1187 doi: 10.4271/2008-01-1187

  • Tanaka, Y., Hiyoshi, R., Takemura, S., Ikeda, Y. et al. (2007) “A Study of a Compression Ratio Control Mechanism for a Multiple-Link Variable Compression Ratio Engine,” SAE Technical Paper 2007-01-3547 doi: 10.4271/2007-01-3547

  • Hiyoshi, R., Aoyama, S., Takemura, S., Ushijima, K. et al. (2006) “A Study of a Multiple-link Variable Compression Ratio System for Improving Engine Performance,” SAE Technical Paper 2006-01-0616 doi: 10.4271/2006-01-0616

  • Takahashi, N., Aoyama, S., Moteki, K., and Hiyoshi, R. (2005) “A Study Concerning the Noise and Vibration Characteristics of an Engine with Multiple-Link Variable Compression Ratio Mechanism,” SAE Technical Paper 2005-01-1134 doi: 10.4271/2005-01-1134

  • Moteki, K., Aoyama, S., Ushijima, K., Hiyoshi, R. et al. (2003) “A Study of a Variable Compression Ratio System with a Multi-Link Mechanism,” SAE Technical Paper 2003-01-0921 doi: 10.4271/2003-01-0921

  • Compression ratio control for internal combustion engine US 5450824 A

  • Grundy, J., Kiley, L., and Brevick, E. (1976) “AVCR 1360-2 High Specific Output-Variable Compression Ratio Diesel Engine,” SAE Technical Paper 760051 doi: 10.4271/760051


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We need zero emission engines that are sustainable not another planet destroyer like this gasser. It is time we start to phase out polluting tech by banning the registration of new non-zero emission vehicles for people and corporations in city areas. Then keep expanding these zero emission zones for new vehicle registrations until all new non-zero emission vehicles are banned altogether from 2025. It will still take another 20 years or until about 2045 before all vehicle air pollution is eliminated as there is a large fleet of gassers that needs to be worn out and scrapped if a total ban on new vehicles is effective by 2025. It is either that or a global warming apocalypse with mass extinction of species that cannot adapt fast enough to a warming planet.

Another advantage of simply banning polluting tech is that we do not need subsidies or taxes that are costly to administrate and enforce. A ban is far cheaper to implement and enforce.

Liviu Giurca

A low cost variable compression ration mechanism for IC opposed piston engines is described on
Contrary to Infinity solution this can be used for the normal cars of the B, C and D segments without to affect dramatically the cost of the vehicle.


We should keep the gasser and this one can be a success if it's more efficient. Some confused leftists and green wannabee are already opposing this gasser provoking a worldwide human economic crash written here in this blog and want to ban the billion gasser for the people.

Brian Petersen

Liviu Giurca, your post is obviously self-promotion since it links to a paper with your name on it. Nevertheless ...

Nissan's solution "packages" in the same shape and size as a normal in-line 4-stroke engine except that the crankcase is a smidge wider - but implementing counter-rotating balance shafts (no longer needed) would also require space down there, so it ends up taking the same space as an in-line engine with balance shafts. No changes to vehicle architecture, same transmissions still fit, etc. Your opposed-piston engine is nowhere near the same shape and size as a conventional engine. And ... Nissan's engine will work with conventional emission controls for 4-stroke spark ignition engines (lambda sensor and 3-way catalyst). Yours, being a two stroke, will not. And two-strokes invariably have problems because of the need for the piston rings to be lubricated and to cross the intake and exhaust ports.

As for the people wanting to simply ban all combustion engines and thus there is no point to improve the technology that we already have ... you are operating in a dream world. Combustion engines are going to be with us for quite a while and we might as well make the best of them.

If Nissan's solution allows a spark-ignition engine to roughly match the efficiency of a diesel engine at part load (and it could) it solves a lot of headaches. I suspect it will be thirsty at full load (in low-compression mode) so this ain't the solution for long-haul trucking, but it'll do for automotive applications (which run at part load most of the time).

Liviu Giurca

Brian Petersen, you didn’t read carefully the presentation. The first described solution on http://www.slideshare.net/giurcal/supercharged-engine
is a four-stroke opposed piston engine. The major advantage for the supercharged version is the huge power density with only one cylinder. This version is also fully balanced and has a very low NVH level without additional balanced shaft and with reduced number of components, meaning low cost.

Brian P

Yes, I will grant that I did not read your self-promotion paper carefully, and I'm not planning to. The main point is that Nissan's development fits within the shape, envelope, and general architecture of a normal in-line 4-stroke piston engine, and yours doesn't. I saw piston-porting in the first diagram in your paper that I encountered, and stopped reading right there. It's problematic for emissions and lubrication. Ask Detroit Diesel.


Will require adaptive fuelling strategy possibly before certainly during and post combustion.

To be able to cope with various fuel quality and (in tank) mixes.

These technology are well enough described and proven but not fully realised.

The tools to bring the fuelling question to production are.

Brian P

Arnold, what are you talking about?

Infiniti's variable-compression system works with a normal DOHC 4-valve cylinder head and doesn't care whether the engine uses port-injection with premixed combustion, direct-injection with premixed or stratified charge, or both. It's also a really good way to facilitate HCCI over a much wider range of speed and load than otherwise possible. It doesn't care what the fuel is ... if anything, this system would allow operation on high percentages of ethanol in high-compression mode, thus taking advantage of the high octane rating of ethanol in a way that today's conventional flex-fuel engines can not. (For example, under given conditions, 87 octane gasoline might limit compression to let's say 9:1, but E85 would allow the compression under the same load conditions to be let's say 12:1, thus improving efficiency under those load conditions.)

Knock sensors are commonplace today. Real-time combustion pressure sensing is not common but it is in production (many current emission-controlled diesels have it). The ability to vary the compression ratio opens up options for how to deal with the detection of knock.

My main concern is combustion turbulence. Modern combustion chambers require the piston to approach the head closely in squish bands around the outside of the chamber, which improves turbulence and accelerates combustion. With this compression-adjustment system, when it is operating in low-compression mode, can't do that, because the piston no longer closely approaches the head!


I suspect that in the high-boost, high-flow conditions when low compression would be used, tumble might provide adequate turbulence.


It looks like you can have efficiency or power, but not both. Maybe they exaggerated with 200 kW and low end torque.

It looks like it will be more efficient to drive this engine in higher rpm with part load (or 70% load), than with WOT at low rpm.


I'm wondering what feedback informs the compression adjustment.
this sketch shows an eccentric shaft But does not mention what turns the shaft.


This shows the 'Harmonic drive'


There are people referencing a 'speed' (or rpm) relationship.

The Harmonic drive is a mystery could it be hydraulically or electrically driven or possibly even respond to engine knock without reference to the engines management computer.
Could the link arrangement be protective against engine knock whilst allowing traditional engine management to manage that.

The reference to agnostic fuel and strategy is made possible as this description from above notes.

"Infiniti's variable-compression system works with a normal DOHC 4-valve cylinder head and doesn't care whether the engine uses port-injection with premixed combustion, direct-injection with premixed or stratified charge, or both. It's also a really good way to facilitate HCCI over a much wider range of speed and load than otherwise possible. It doesn't care what the fuel is ... if anything, this system would allow operation on high percentages of ethanol in high-compression mode, thus taking advantage of the high octane rating of ethanol in a way that today's conventional flex-fuel engines can not. (For example, under given conditions, 87 octane gasoline might limit compression to let's say 9:1, but E85 would allow the compression under the same load conditions to be let's say 12:1, thus improving efficiency under those load conditions.)

Knock sensors are commonplace today. Real-time combustion pressure sensing is not common but it is in production (many current emission-controlled diesels have it). The ability to vary the compression ratio opens up options for how to deal with the detection of knock.

Aside the introduction of an extra task to shift the compression, which in it self needs some sort of feedback,
so another layer of engine management, there is also an expectation that fuels and fuel air mixes will have a much larger range than expected by today's ICE engines.

I assume that the control shaft will be under computer control? possibly via the hydraulic? "harmonic drive"?
It is likely to be responding many times slower than the injectors and timing which can respond within one cycle.

It's important to protect against damaging knock while running as close to the limit as possible.


Might it not benefit from fuel monitoring at the tank.
If appropriate fuel quality sensing (on a chip) were available it would seem useful on this VCR engine.


To burn a range of hydrocarbon fuels - why not?

As a classic VCR engine these were desirable for engine developers and chemists.

They say it is production ready the fruit of twenty years of development.

But that's not the same as ready to deliver the suite of potential benefits.

Will it return significant improvements over current designs? In some important areas potentially yes.

Hybrids and VVT can return the much of the fuel efficiency.

Electric motors with one or two moving part or four with gear train are in a whole other league.


The most likely way to turn the eccentric shaft is a hydraulic piston supplied with engine oil.


That does seem to be most likely.

'Harmonic drive' likely refers to the shape of the 'waveform'(for lack of better analogy) described by the changing centres of the crank pins.

Till more is revealed, end of Sept this is an engine minus comprehensive engine management or ratio control strategy.

Brian P

A harmonic-drive gearbox is a type of high-ratio gear reduction unit (100:1 gear reduction is possible in a single stage). A stepper motor would be the most likely choice to operate that, and yes, the motor would be under direct ECU control. It is also possible to do it hydraulically based on engine oil pressure through a directional valve; VVT mechanisms already do this. It seems from the diagram that Nissan has chosen a harmonic drive reducer which would almost certainly be driven by a stepper motor. Stepper motors are already in common use for actuators that require high positioning accuracy (which this does). If high positioning accuracy is required, the hydraulic method is not so easy. VVT mechanisms use hydraulics because the adjustment has to be done inside a rotating assembly (the camshaft and drive pulley/sprocket).

Controlling the position of an axis (the variable-compression mechanism) via a stepper motor in response to any inputs you care to choose, is a trivial exercise for modern engine control units. Feedback via knock sensor is almost certain to be part of the control strategy.

Ignition timing would remain part of the knock strategy because it can respond on the next engine cycle, whereas the compression adjustment mechanism would take longer to react. Again, this is not a problem for modern engine controls. The ignition timing control loop is the "fast" response and the compression ratio control is the "slow" response.

As for air/fuel ratio ... Given how the standards have been written and how the engineers have figured out how to (mostly) comply with them, this ain't gonna change. The standards have locked us into stoichiometric air/fuel ratio with lambda sensor and 3-way catalyst. You can play with exhaust recirculation, either via an explicit EGR system or by cam timing trickery, but air/fuel ratio remains stoichiometric. The variable compression mechanism in no way changes or affects this. Even if HCCI is used, it will still be stoichiometric, just with varying amounts of EGR - so that it can use a normal 3-way catalyst. Nothing else that we know how to do, is sufficiently future-proof. (Ask VW.)

I agree with the statement that you can have efficiency or power, but not both simultaneously ... unless you are using high octane fuel (like E85) ...

Modern engine controls, with knock sensors and lambda sensors, can figure out what mix of fuel is in the tank (within reason) without actually measuring what the fuel is. Gasoline is such a concoction of different compounds that measuring its properties in the fuel tank isn't all that reliable. But the knock sensor and the lambda sensor are enough to tell the engine controls what they need to know. The person who puts diesel fuel into the tank of a spark ignition engine is gonna be in trouble no matter what.


Certainly you can have efficiency and power at the same time.  You use the turbocharger to get a 3:1 or greater compression ratio, use variable compression and VVT to achieve perhaps a net 15:1 CR with a 20:1 or greater expansion ratio, and run the turbocharger off the remaining expansion energy in the exhaust gases.  It's quite possible to run with substantially lower exhaust back pressure than intake MP, so the piston engine operates partially as an expansion stage of a turbo air pump.

Brian P

That's the Atkinson (or Miller, if you wish) cycle. Nothing in Nissan's variable-compression-ratio system precludes the use of cam timing trickery to achieve Atkinson/Miller cycle operation.

The "efficiency versus power" tradeoff relates more to cylinder pressure and detonation limitations. It can only operate at a very high compression ratio at lighter load on the engine (when boost pressure is low and intake is restricted - whether by throttle or by cam timing trickery is irrelevant). It becomes detonation-limited and peak-cylinder-pressure-limited at high engine load which means the compression ratio must be lowered (and BSFC suffers).

You can rest assured that Nissan already knows how to do the Atkinson/Miller cycle, and they already know that they want to use the highest compression ratio that can practically be achieved under given operating conditions.


Something else that occurred to me while I was road-tripping is that the crankshaft throw is about 50% of that of a conventional engine.  The up-down motion is amplified 2x by the lower link, but the side-to-side motion is not.  This means less connecting-rod angle, less side force on the piston and less friction.


Sometime later 2nd Sept.

This is a similar engine.
Describing a Dual ratio Hydraulicaly actuated "little end eye" WTF? with pressure sensing.

It will need after treatment for pollution control same as standard engine so is as with all the attempts to clean up heat engines - going down the path of more complication.


He described FEV's 2-step VCR, which offers a 3-5% increase in fuel efficiency, as “a relatively big ‘hammer’ to employ for CO2 reduction. It can significantly extend the operating window, allowing you to operate at higher power levels without incurring (engine) knock.”

With the expanding European test program, the VCR technology is “gaining momentum” toward productionization, with FEV in discussions with potential Tier 1s, Tomazic noted. The modular technology can be adopted as a clean-sheet or retrofit for diesel, gasoline, flex-fuel engines in any cylinder configuration.

FEV has been in the vanguard of VCR design, development and testing since the 1990s. In 2009 the company published an SAE technical paper (http://papers.sae.org/2009-01-1457/) describing the 2-stage VCR system now under test by OEMs. The mechanical centerpiece is a clever adjustable-length connecting rod featuring a rotating eccentric eye within the rod’s “little end.”

“It’s a simple, passive system, requiring just a bit of hydraulics and a 2-way valve to lock the system into positions ‘A’ and ‘B,’” Tomazic explained. The con rod’s unique design incorporates two small hydraulic pistons, each within a dedicated chamber; the hydraulics in the two small cylinders serve only as a locking function to stabilize the mechanism in the ‘A’ position.

“We basically drain one chamber and make the other one accessible to low-pressure oil that comes through the crankshaft and the con rod into that chamber,” Tomazic said. The chamber fills up and the oil flows back through a check valve. The primary (large) piston is moved up and down relative to the rod exclusively by the mass and inertial forces.

Transitioning from compression ratio ‘A’ to ‘B’ is achieved within 0.2 to 0.6 s. According to Tomazic, a typical ratio change in a gasoline engine would be from 11:1 to 15:1. The piston’s maximum vertical lift threshold of 1.5 to 2 mm (.06 to .07 in) is adjusted in real time according to load and available fuel quality, via inputs from knock and fuel-octane sensors.

FEV engineers have evolved the VCR using one of the company’s proprietary analysis toolsets known as CMD (Charge Motion Design), based on optimized CFD. Compared with fixed-ratio and full-variable compression-ratio designs, the 2-stage VCR enables higher potential fuel economy in spark-ignited ICEs, particularly as average peak firing pressures (up to 170 bar/2466 psi) increase.

Some powertrain engineers have commented that even with the presumed cost benefit of mass production, FEV’s sophisticated con rod would be many times more expensive per unit than a current-production conventional steel rod. Tomazic argues that the greater complexity is part of the industry’s investment in advanced ICE technologies to meet the next phase of CO2 regulations.

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