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Nissan to Introduce New Engine Valve Control Technology on Infiniti G37 Coupe; Up To 10% Efficiency Gain

29 March 2007

Vvel
The VVEL system. Click to enlarge.

Nissan Motor is combining its newly developed Variable Valve Event and Lift (VVEL) and continuous valve timing control (C-VTC) technologies to deliver enhanced efficiency and performance. The first product to feature the VVEL technology will be the Infiniti G37 coupe, scheduled to be unveiled at the upcoming New York International Auto Show.

Nissan had earlier announced plans to install the VVEL system, which contributes up to a 10% reduction in fuel consumption and carbon-dioxide emissions compared to an engine of the same displacement without VVEL, on its products worldwide starting from FY07 under the Nissan Green Program 2010. (Earlier post.)

In the VVEL system, a rocker arm and two types of links close the intake valves by transferring the rotational movement of a drive shaft with an eccentric cam to the output cam. The movement of the output cam can be varied by rotating the control shaft within the DC motor and changing the fulcrums of the links. This makes a continuous adjustment of the valve lift amount possible.

While conventional engines control air intake using a throttle valve, VVEL-equipped engines do this directly at the intake valves, continuously controlling their valve events and lifts.  C-VTC and VVEL together control the valve phases and its valve events and lifts, allowing free-control of the valve timing and lift.

This results in more efficient airflow through the cylinder and improves responsiveness, optimizing the balance between power and environmental performance:

  • Higher fuel efficiency. At low-to-mid load ranges, the system controls air intake at the intake-valve, immediately before it enters the combustion chamber, in contrast with conventional engine air intake via a throttle valve, leading to increased efficiency by easing airflow through the cylinder. In the low- and medium-rpm ranges, intake-valve lift is kept low to reduce camshaft friction and improve fuel efficiency.

  • Better response. Controlling air intake at the intake-valves improves acceleration response by allowing more dense air into the cylinders from the start of acceleration.

  • More power. In the low-rpm range, the intake-valves open for a shorter period, preventing blowback of the air-fuel mixture and improving torque. In the high range, greater intake-valve lift allows increased air intake to deliver greater torque outputs.

  • Cleaner emissions. Intake-valve timing is optimized on startup, when the engine is still cool, to quickly raise the temperature of exhaust gases and more quickly activate the catalytic converter.  Hydrocarbon emissions are reduced in the low-to-medium range by keeping intake-valve lift low, speeding intake flow and dispersing the fuel into a fine mist, resulting in more efficient full combustion.

VVEL improves fuel efficiency most effectively in the low-to-medium operating range, thus it is best matched to the multiple-cylinder and higher displacement engines that typically operate within that range, according to Nissan.

Under the Nissan Green Program 2010, Nissan has announced plans to develop gasoline-powered engines with CO2 emissions reduced to levels comparable with diesel engines, to be available globally by 2010.  For multiple-cylinder, high-displacement engines, Nissan will combine VVEL technology with a gasoline direct-injection system.

March 29, 2007 in Engines, Fuel Efficiency, Vehicle Systems | Permalink | Comments (8) | TrackBack (0)

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Comments

I assume this is cheaper than full electric camless?
http://www.greencarcongress.com/2006/12/valeo_in_develo.html

It's being implemented, so, safe to say the cost benefit analysis is favorable to implement this tested and proven
efficiency upgrade. Look to a wider application, to see if consumers embrace this innovation, before the full electric
group of components under the hood, is the obvious next step.

It's being implemented, so, safe to say the cost benefit analysis is favorable to implement this tested and proven
efficiency upgrade. Look to a wider application, to see if consumers embrace this innovation, before the full electric
group of components under the hood, is the obvious next step.

This is a better idea than what GM, DaimlerCrysler and Honda do with shutting off 1/2 the cylinders under low load. It keeps cylinder walls at temperature and you don't have the frictional losses associated with pistons performing no work.

You can't do both in one engine (unless you use electromagnetic valves)

Quite ingenious mechanics.

As I understand, direct injection gasoline engine does not require continuously variable valve lift. Valves could open to their max position, and amount of air charge could be effectively regulated by duration of valve opening alone. Anyone?

BMW has had fully variable valve lift for some time now, which is what you need if you want to keep your throttle wide open at all times. Porsche and Honda make do with cheaper systems that offer just two valve lift settings.

Valve deactivation reduces pumping losses by running a subset of the available cylinders at higher load. This is cheap to do in V engines with at least six cylinders, especially if they feature pushrods. The systems switch back and forth between the banks every few seconds to keep the entire engine block warm at all times. The main drawback is the impact on engine sound - customers want to hear that big V8 they paid for.

Andrey -

I'm not sure if GDI is strictly necessary for electromagnetic or electrohydraulic camless valve train systems. Those are quite expensive and are currently only used in research engines.

With a purely mechanical fully variable lift solution such as the one described above, no-one has yet managed to also fit a second-generation spray-guided GDI concept in the cylinder head. First-gen GDI concepts featuring lateral injection and specially shaped piston crowns would still be feasible.

Afaik, both Mercedes and BMW are revisiting stratified GDI rather than trying to combine it with fully variable valve lift. Globally lean combustion in part load implies lean-burn NOx aftertreatment.

Now to wait for the "trickle down" effect. It is great that you can get a lower end BMW with Valvetronic now (started on the 7 series and is now available on the 1 series)...if this is a success for Nissan it would be a nice addition to their 1.8L and 2.0L engines as well.

Patrick -

trickle-down will happen. Europeans can now buy Valvetronic technology in the new Mini and a number of Peugeot models, thanks to the BMW-Peugeot engine JV.

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