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Toyota Announces New Intake Valve Lift and Timing System

12 June 2007

Valvematic
The Valvematic system. Click to enlarge.

Toyota Motor has announced its new variable valve lift mechanism, which it calls Valvematic. Valvematic combines the existing VVT-i (Variable Valve Timing-intelligent), which continuously controls intake valve opening/closing timing, with a new mechanism that continuously controls the intake valve lift volume.

In the case of a new 2.0-liter engine developed by Toyota, Valvematic improves fuel efficiency by 5% to 10% (depending on driving conditions), reduces CO2 emissions, boosts output by at least 10% and enhances acceleration responsiveness, according to the company.

TMC plans to introduce Valvematic shortly, starting with a new vehicle model featuring a 2.0-liter engine.

Valvematic adjusts the volume of air taken in by continuously controlling the intake valve lift volume as well as the timing of valve opening and closing. This boots performance based on the engine’s operational condition, helping vehicles achieve better fuel efficiency and dynamic performance.

Conceptually, this is similar to BMW’s Valvetronic, which also provides infinitely variable valve lift and timing, and delivers an approximate 10% reduction in fuel consumption. To implement Valvetronic, BMW uses an additional eccentric shaft, an electric motor and several intermediate rocker arms.

In 2006, Honda outlined its next-generation approach to valve lift and timing: Advanced VTEC (Variable Valve Timing and Lift Electronic Control System). A-VTEC also combines continuously variable valve lift and timing control with the continuously variable phase control of VTC (Variable Timing Control) to achieve a 13% improvement in fuel efficiency, compared to a production 2.4-liter i-VTEC engine. (Earlier post.)

Nissan also recently introduced its new Variable Valve Event and Lift (VVEL) and continuous valve timing control (C-VTC) technologies, which will be first applied on the Infiniti G37 coupe.

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.

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. (Earlier post.)

June 12, 2007 in Engines, Fuel Efficiency, Vehicle Systems | Permalink | Comments (30) | TrackBack (0)

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Comments

I wasn't said but does this eliminate the throttle valve as in the Valvetronic system?

From the release by Toyota, it sounds like the throttle butterfly is eliminated:

"While conventional engines control air intake using a throttle valve, Valvematic adjusts the volume of air taken in by continuously controlling the intake valve lift volume and timing of valve opening and closing"

"While conventional engines control air intake using a throttle valve, Valvematic adjusts the volume of air taken in by continuously controlling the intake valve lift volume..."

So if the air volume is adjusted by the valvetrain, it doesn't need a throttle. It's more explicit on the Toyota press release.

Great minds think alike!

I wonder if this technology will be incorporated in their hybrid line. An additional 10% GPM improvement on a hybrid would be awesome!

A series hybrid will not need an engine with variable timing.

@ shigley:

Implementing the throttling functionality via continously variable valve lift (CVVL) is most effective in low part load. In a full hybrid, the drivetrain managemen system is set up to artificially add load via the electric generator in that scenario, permitting the ICE to be shut off entirely for a short period a few minutes later.

Ergo, combining CVVL and full hybridization makes little sense. Miller/Atkinson cycles, which do, are implemented via ordinary variable valve timing (VVT). Only a few fuel economy technology combos have proven synergies, e.g. downsized displacement + turbocharging + homogenous GDI + VVT.

Also, the extra cost of continously variable valve lift is not negligible and undesirable in a car that already sports an expensive hybrid system. Remember, it's not about creating the most efficient design! rather, it's about getting modest but affordable improvements into as many new vehicles sold as possible. If CVVL becomes standard in e.g. the Camry, it may do more to wean America off foreign oil than all the hybrids combined.

Rafael: Thanks for the education.

Imagine if something like this were incorporated into the large displacement V6 and V8 pushrod engines that GM and Chrysler still build by the hundreds of thousands.

Hehehehehe........ Keep your eyes peeled.

I wish that this technology along with cylinder deactivation could be retrofitted into my '05 Acura RSX.

To shigley and Rafael
There are many ICE technologies that would not be cost effective in a hybrid vehicle. They include cylinder deactivation, instant on/off (flywheel or belted alternator/ starter). It is also unlikely that the cost of a homogeneous charge compression ignition engine or diamond like low friction coatings on tappets, rings, liners etc. would be cost effective in a hybrid.

Hi All,

One has to wonder if a poppet throttle valve would be advantageous. The aerodynamics of the butterfly valve are just horrendous. If one made a tear-dropped shapped poppet, with a sealing surface, one could possibly reduce the turbulence in the intake plumbing dramatically. This might be implemented more cheaply than the engine valve variable opening.

Toyota's approach is doing this, by using the engine poppet valves. So there is no need for a good aerodymic shape - one wants turbulence in the cylinder. They do save the expense of the electrically operated throttle valve.

And lets remember, the engine is still throttled, so there are still pumping losses. Just less pumping losses due to the intake air flow being smooth till it goes into the cylinder. As one might be able to achieve with an aerodymic throttle. Might be a good retrofit project for a manually controlled throttle engine.

Rafael - none of this technology recovers braking energy. And as one that actually drives around the US, I can tell you first hand that "stop, wait, wait, go, and stop again", is a large consumer of gasoline here. 10 % is only 1/8 th the improvement the Prius achieves. We are talking about 3.4 mpg, or 37.4 mpg instead of 34 mpg on a Camry, right !?


"In a full hybrid, the drivetrain managemen system is set up to artificially add load via the electric generator in that scenario"

Rafael - can you really generalize everything like that? There are hundreds of possible factors that will affect how the ICE and electric powertrains interact. In fact, I think the hybrid drive would only add such additional loads if the battery levels were below a certain point.

Even with Toyota's hybrid system, there are many cases where the ICE is almost exclusively powering the vehicle, like extended highway driving. Excluding the Prius, most of their hybrid applications still have an oversized ICE that is often going to be operating under low loads during steady state cruising. Why wouldn't you want to maximize the efficiency of the ICE during those times?

I'd have to think that if a variable lift system was utilized, they would make adjustments to how the hybrid system worked. You cannot tell me this would not help. In fact, one of the chief complaints of Toyota's system is that it does less to improve highway cruising than other types. This sounds like it could help to address that.

donee,
The advantage of variable lift valve is that the valve lift is reduced at low intake flow, thereby maintaining turbulence in the intake air/fuel for proper mixing in order to promote efficient combustion with minimum emission of PM and HC.

Furthermore, if engine intake is done behind a throttle valve, the piston is working against partial atmospheric pressure for the entire intake stroke.

However, if variable timing valve is used without a throttle plate, so as to allow the intake valve to close in the middle of the intake stroke, then the piston is NOT working against partial atmospheric pressure for the initial part of the intake stroke, while the partial vacuum in the remaining of the intake stroke will be cumulative a lot less than the partial vacum behind the entire intake stroke behind a throttle plate. (the integration of the differential of the instantaneous force experienced by the piston multiply by the distance the piston travel for the rest of the intake stroke will be a lot less than the constant partial vacuum experienced by the piston for the entire intake stroke.)
The turbulence behind the throttle plate does not account for a large percentage of pumping loss.

Rafael has a good point in that a full hybrid has the engine running at high manifold pressure (low manifold vacuum) for most at the time, and that the engine is shut off during coasting, thereby pumping loss will be quite low. Furthermore, a full hybrid allows the engine to be used at a more constant power setting, in which the valve lift can be tuned for maximum efficiency, thereby, there will be little to be gained in return for the additional cost and complexity of variable lift mechanism. Transient power demand can be partially met by power of the battery and electric motor.
But, of course, full hybrid is more expensive hence limit large scale adaptation. So, if a simpler and cheaper mechanism that can be more widely adapted in order to reduce fuel consumption, then it would be just as good.

Roger:

In addition to reduced pumping losses if early closure of intake valve eliminates throttling, most (not all) of energy lost by piston working against partial vacuum in cylinder after intake valve closure will be recuperated by less energy spent in compression stroke.

And even with infinitely variable transmission and generator ICE output leveling gasoline engine in full hybrid does not work on full throttle. Too much noise, harshness, too high exhaust gases temperature, too much wear on mechanical parts. So yes, Valvematic will be beneficial to full hybrid too, just less than to regular car.

Interesting combination could be Atkinson cycle lean-burn GDI, VVT-I, and full hybrid drivetrain combination. Lean-burn GDI is quite on full throttle and exhaust gases are cooler. GDI does not require variable valve lift (no need to maintain high charge speed/turbulence to mix and evaporate port-injected gasoline), so just VVT-i will suffice. Varying engine RPM independently of vehicle speed, intake valve timing, fuel/air ratio in lean-burn mode, and output of generator – all together will allow ICE to work in most efficient mode without throttling almost at all operation conditions.

"continuously controls intake valve opening/closing timing"

With the Valvematic system on an Atkinson cycle engine, wouldn't it be variable compression ratio?

This is what Mazda is doing with there 1.3l engine.

http://www.mazda.com.au/articleZone5.aspx?articleZoneID=3817

"With the Valvematic system on an Atkinson cycle engine, wouldn't it be variable compression ratio?"

I've thought about the same thing. With all the talk about finding a way to better optimize engines for combustion on ethanol, to take advantage of the higher compression ratios that can be used, I would think that could be one way to do it.

Wouldn't running in an Atkinson cycle effectively lower the compression ratio? Wouldn't that mean you could increase the basic compression ratio to the levels that increase the thermal efficiencies when running on ethanol, well beyond those that gas would support, and then run the Atkinson cycle when you weren't using ethanol (or enough of a blend)?

I know people wouldn't like the idea of getting less torque when running on gas, but this could encourage ethanol use. This seems similar to Saab's biopower concept that uses increased turbocharging to increase power when using ethanol.

Andrey,
Good point regarding high exhaust gas temperature on engine running at high throttle setting (high manifold pressure), but Atkinson cycle allows more expansion of exhaust gas, hence will reduce exhaust gas temperature and pressure somewhat, with concomintant reduction in noise and harshness. So, it appears that Atkinson cycle is a must-have for a full-hybrid vehicle, because engine efficiency map reveals that peak efficiency won't be reached til 70-80% of maximum manifold pressure is used. A non-hybrid vehicle in highway cruise will use 1/2 or less of the manifold pressure required for peak efficiency.

GDI would be great if means other than 3-way catalytic converter is used to reduce NOx, because it won't work on lean combustion with excess O2 remaining in the exhaust. Perhaps Honda's scheme for NOx reduction for Diesel engine can be used for GDI, so it would be a quite promising means to raise the efficiency of gasoline engine to par with Diesel engine without some of the disadvanges of Diesel engine. In that way, GDI with Atkinson cycle would be great to complement a full-hybrid drive train.

Angelo,
So far, it appears that ethanol is a deadend, since it takes nearly as much fossil fuel to produce the ethanol.

"So far, it appears that ethanol is a deadend, since it takes nearly as much fossil fuel to produce the ethanol."

I'm not going to stoke that fire too much, because I know how many people are passionate one way or another, but I still feel compelled to respond. That statement is only marginally relevant if you limit your discussion to corn-based ethanol that utilizes outdated techniques. Clearly, not the future of the ethanol industry. It also assumes all types of fossil energy is equal, which is not the case in terms of emissions or politics (a good portion of the fossil fuel inputs for ethanol is domestically-sourced and relatively clean natural gas).

Regardless, the numerous large private investments into ethanol suggest it is far from deadened.

Serial hybrid direct drive to extender engine with NIMH batteries and a simple turbocharged GDI engine optimized for one speed (high) with no throttle plate, waste gate, variable valve tim. or other nonsense.

Forget trying to get a half percent here or there with the mice on a wheel. Put in absorption air conditioning and or the BMW steam turbine to use othe other 75% of the fuel going out the stack or the radiator! I do know about mass being an inital problem for the first generation.

Rafael:
Please correct me.

Ethanol or not this is a simple VCR system with current technology.

Angelo,
The future of ethanol is from cellulosic sources. But, for all the trouble of using expensive enzymes to break the strong cellulose bond, these cellulosic biowaste can be gasified to produce H2 for direct consumption, or H2 and CO product of gasification process can be used to synthesize liquid fuels (methanol, ethanol, and HC)to fuel current vehicular fleet, until H2-capable vehicles will roam the streets.

Joe,
Since I share the same opinion as Rafael in this subject, I would like to equate your idea to the GM Volt serial hybrid using a 16kwh battery, with A123 battery now costing $2000 USD/kwh, making battery cost alone $32,000 USD. Adding yet-to-be-proven motor and controllers and engine, and the price tag may hit $50-60,000 USD. How many of these will be sold?

Whereas for $16-18,000 USD, you can buy a Toyota Camry with VVT-i right now, and soon to be equipped by the millions with Valvamatic variable lift together with VVT-i, with 10% or higher efficiency improvement. This will translate to billions of gallons of gasoline saved. Which car will save more fuel?

Roger,
It's tough to dismiss ethanol produced through enzymes merely because they are expensive now. The costs would come down considerably once they settled on the correct ones to mass produce. However, I have no problem with gasification - whatever turns out to be the most efficient route. I just don't think we know enough about cellulosic ethanol at this point to dismiss it. We should be promoting everything that has the potential to replace a portion of our fossil fuels, in my opinion. Economics will then sort everything out.

Angelo,

You had a very sage statement that bears repeating;

"We should be promoting everything that has the potential to replace a portion of our fossil fuels, in my opinion. Economics will then sort everything out."

Unfortunately, government jacka$$ses of the party that beleives in price controls, will mandate prices for thier politically correct technologies. Thus distorting the selection of the best economic solution.

As an example of this proposition. Look at the the Democrats under Clinton withdrawing the US from international Thermonuclear fusion research in order to spend money studying wind and wave and suntans. It set back Fusion by more than a decade, before the sane ones resurrected ITER from the Dead. The Bush DOE and State Department recreated and EXPANDED the international cooperative effort to include most of the developed and partially developed world. With Korea Japan, China, India and Brazil added to the US EU and Russia, ITER is finally being built.

Inexhaustible clean electricity Fusion plants would make a great combination to provide the motive power for PHEVs and BEVs. We could have had them by the late teens. Now not until the early thirties,at best. Thank You Mr. Clinton for not paying attention, and wasting a decade.

Stan,

Wow, that's got to be a first on GCC: Democrat-bashing. It's a welcome change from the incessant Bush-bashing that is the norm around here. You can also thank the Clinton adminstration for funding the multibillion-dollar PNGV (80mpg family sedan)- which amounted to nothing more than corporate welfare for GM Ford and Chrysler (allowing them to continue their gas-guzzling status quo).

Back on topic: anyone know what applications this 2.0 liter engine will find here in the US market? A 2.0 liter Corolla (offering more performance while returning 1.8 liter or better economy) would be nice!

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