New York Preview: Nissan to introduce new variable valve timing tech
by Dan Roth on Apr 1st 2007 at 11:29AM 
Ever-tightening emissions requirements, teamed with consumers' lust for today's high horsepower numbers, have led to some creative valve timing and lift schemes. Infiniti's G37 will be pack some interesting tech underhood when it debuts at the upcoming New York International Auto Show. There are actually two new developments working in conjunction to give independent control over valve timing and lift. Nissan has dubbed the control technologies Variable Valve Event and Lift and Continuous Valve Timing control, or VVEL and C-VTC, respectively. VVEL uses a clever arrangement of links to actuate the valves, and moves the fulcrum for the links via a seperate shaft actuated by a DC motor. By moving the fulcrum, the valve lift is varied. More after the jump, along with press release
[Source: Nissan via Gizmag]
Nissan's new valve actuation arrangement allows efficiency gains to be realized. Out go the throttles and their pumping losses, unnecessary now that the valve action can control engine speed. Without a throttle plate, engine responsiveness increases; not that the VQ with throttles is slow to respond to jabs at the go-pedal. CO2 emissions also see a 10 percent reduction with VVEL. The largest gains are realized in the low and middle RPM range, but the top end doesn't suffer, either. The ability to increase valve lift allows higher torque output at high RPM.
Of course, this technology has some of the same gotchas as gasoline direct injection – cylinder pressures and temperatures must be attended to during tuning and development to keep emissions in bounds. One neat trick for cold starts and quick warmups is that the VVEL and C-VTC systems will optimize the valve events to quickly put heat into the exhaust gas, lighting off the catalytic converter faster. Tuning voodoo has also led to using reduced valve lift in that low to mid RPM range to increase the velocity of the intake charge, improving fuel dispersion and atomization for more complete combustion.
The VVEL and C-VTC systems are part of Nissan's Green Program 2010, which aims to reduce gasoline engine CO2 emissions to the level of diesel engines and have the technology on sale globally by 2010. How's that for having your cake and eating it, too? The G37 will run cleaner and be able to twist the tires right off the rims even better. We wonder if the engine emissions reductions will offset all that tire smoke?
PRESS RELEASE:
Nissan Introduces Innovative Valve Control Technology [Mar. 29, 07]
- Variable Valve Event & Lift (VVEL) delivers significant improvements in dynamic and environmental performance -
TOKYO (March 29, 2007)--Nissan Motor Co., Ltd. today introduced a new engine technology that delivers a balance of responsiveness and power, fuel efficiency and low emissions. The new system combines the technologies behind Nissan's newly developed Variable Valve Event and Lift (VVEL)*1 and continuous valve timing control (C-VTC) to deliver significantly enhanced performance. This advanced technology will be available to customers worldwide through the Nissan and Infiniti product lines.
Nissan announced plans to install the VVEL system, which contributes up to a 10%*2 reduction in carbon-dioxide emissions, on its products worldwide starting from FY07 under the Nissan Green Program 2010. The first product to feature the VVEL technology is the Infiniti G37 coupe, scheduled to be unveiled at the upcoming New York International Auto Show in April, 2007.
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 significantly improves responsiveness, optimizing the balance between power and environmental performance.
The new engine offers the following advantages depending on driving range:
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*3, 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.
l 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.
The 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.
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 the direct-injection system.
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.
*1 VVEL: Variable Valve Event & Lift
*2 This percentage improvement is measured by Nissan by comparing an engine with the VVEL system to an identical engine without it.
*3 The accelerator pedal is pressed halfway or less.
Reader Comments (Page 1 of 2)
G37 11:39AM (4/01/2007)
Come discuss VVEL and the G37 at http://www.gcoupe.com/
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david 11:47AM (4/01/2007)
Just one more thing to break on a Nissan.
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Tal 1:18PM (4/01/2007)
#2
I'm not familiar with other things that break on a Nissan but when I read the intro about this varible valve timing system feature, my first thought was : this sounds complicated and inticate enough that it will be a problem. I am certainly no engineer by any stretch of anyones imagination but , I don't know.... time will tell.
Truely hope it is a durable system that works without any problems . I would love to own a G35 or G37. At leasr the G35 is proven.
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Chet 2:24PM (4/01/2007)
Anything that improves the efficiency of "high-displacement" engines at low loads gets a big thumbs-up from me. Consider this the inverse of hybrid technology -- and compared to hybrid technology, this is UNcomplicated.
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doglet 3:12PM (4/01/2007)
getting rid of the throttle is long overdue, imagine if you had to control your breathing putting your hand over your mouth instead of just not breathing as hard. if you have good enough control of the valves, there shouldn't be anything between the airfilter and the back of the valve.
sure its a little more complicated but when efficency and torque are the benefits, who can complain?
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shimman 4:37PM (4/01/2007)
does this mean that the newly released vq35 be discontinued alone with g35 name?
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Eisenfaust 3:15PM (4/01/2007)
Does Yamaha help out with Nissan's cylinder head development, the way they do/used to with Toyota?
Yamaha patented an almost identical system about a year and a half ago.
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Jason 3:25PM (4/01/2007)
The article is incorrect about completely removing the throttle butterfly. Read this quote:
"The V-6 retains a conventional throttle butterfly, but it's used for emissions-related purposes only, according to Nissan."
Source:
http://www.automobilemag.com/auto_shows/2007_new_york/0703_2008_infiniti_g37_coupe/
BMW engines with Valvetronic on the other hand completely remove the throttle butterflies.
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AMcA 3:32PM (4/01/2007)
OK, GM. Beat this!
Does anyone know what happened to the electro-mechanical infinitely variable system that was supposed to appear on the C-class?
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naggs 4:27PM (4/01/2007)
"Does anyone know what happened to the electro-mechanical infinitely variable system that was supposed to appear on the C-class?"
same thing that happened to unicorns and the car that runs on water
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hehe 4:39PM (4/01/2007)
Vive la Nissan!
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MikeW 5:57PM (4/01/2007)
BMW still has a throttle with valvetronic.
http://www.bmwusa.com/Vehicles/7/750liSedan/HighlightDetail.htm?id=192
The throttling with this system and valvetronic is moved from a butterfly to the valves. It is just less inefficient.
BMW has plenty of roller followers in its design. Too bad BMW has made direct injection and valvetronic mutually exclusive. Although BMW could change strategic direction and retorfit valvetronic with 'high precision injection' they could lay that piezo injector down and have the nozzle between the two intake valves. Get that compression ratio up.
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strangway 6:20PM (4/01/2007)
I think the key to truly low CO2 emissions will be using this system in small displacement engines. Just as BMW uses turbochargers, Nissan should use this to save fuel and preserve power.
Maybe a future Sentra can use a 1.6L VVEL/C-VTC to get 160hp and get 40mpg.
It's no TSI twincharger, but it still sounds cool. "Way to go, Nissan!" :p
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jrm1493 6:51PM (4/01/2007)
actually, as an engineer, the system looks pretty simple. the only thing that is looks like a likely failure is the electric motor, and depending on where that fails the engine may still run ok until it can be repaired (especially if the other cylinder bank is doing fine). if they want to make this fail safe just have two motors that are fully capable of driving the shaft with the other failed, and set off the check engine light when driving currents indicate a failure of one motor.
one thing though is that the heads on these motors are going to be monsters, even compared to regular DOHC heads. hopefully they can fit them and still leave the car serviceable.
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your ad here 10:56PM (4/01/2007)
Honda claims its VTEC has never failed once on any car so equipped!
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Barney 12:25AM (4/02/2007)
This is advancement. I recall the cars of the eighties, when manufacturers tried all sorts of plumbing on a conventional engine for pollution control.
Re #16 post by dustin. I think he drives a Lada or an American equivalent.
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Jason 1:08AM (4/02/2007)
They've already had this in Japan for a while on the SR20 motor. Its called NeoVVL and the motor is the SR20VE and SR20VET. And its a common motorswap for SR20 powered cars. It works VERY WELL.
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Jim 7:46AM (4/02/2007)
Kind of funny (ironic, not ha ha) that Nissan is bragging about this system reducing emissions while they are increasing the engine size at the same time. Strangway in post 13 is right, the best way to reduce emissions is to decrease engine size. My current car is a 2.4L 4 banger, more HP (+5) and better MPG (+6) than my 1990 3.0L V6. Why go to 3.7L, wasn't 300HP enough?
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MikeW 9:35AM (4/02/2007)
Come on down 350Z track model ! you're the next contestant on the showcase showdown.
ahhh, yeeeeh wee. Please remember to have your crossplane crank V8s spayed or neutered.
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Roger Dalrymple 10:31AM (4/02/2007)
Let me see now, if I reduce the size of my engine to reduce emissions I can get an even greater reduction because no one will buy my car. That's it! I'll just go out of business. Zero emissions!!
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