Green Car Congress  
Go to GCC Discussions forum About GCC Contact  RSS Subscribe Twitter headlines

« Novozymes and Novo Nordisk utilize wastewater to produce biogas | Main | DOE to issue funding opportunity for R&D for hydrogen storage for vehicles, material handling and portable power »

Print this post

New 2014 Toyota Corolla brings Valvematic, new CVT to North America; up to >40 mpg highway

7 June 2013

2014_CorollaLE_Eco_001
2014 Toyota Corolla LE Eco. Click to enlarge.

Toyota unveiled the 2014 Toyota Corolla—the 11th generation of the car. With nearly 40 million units sold, the Toyota Corolla is the world’s best-selling car nameplate; this year marks its 47th year on the market.

The 2014 Corolla is available in four distinct grades: L, LE, S, and the new LE Eco grade. The LE Eco grade is differentiated by a more efficient 140-horsepower, 1.8-liter engine with Valvematic technology; improved aerodynamics; and low rolling resistance tires. The Corolla Eco-badged models will achieve an estimated highway fuel economy rating of more than 40 mpg (5.88 l/100km) due to to the new Valvematic engine combined with a newly developed Continuously Variable Transmission (CVT).

The 2014 Corolla offers two 1.8-liter, all-aluminum four-cylinder engines. The base 1.8-liter unit with VVT-i is available on the L, LE, and S grades and is rated at 132 hp (98 kW). The Corolla’s new LE Eco trim level is equipped with a 1.8-liter engine with Valvematic—a further development of VVT-i—a valve train technology which appears for the first time in North America with Corolla.

Valvematic offers a broader range of continuously variable valve timing (lift and phasing) to provide optimal intake valve (not on exhaust side) operation relative to engine demands. Valvematic offers more than a five-percent improvement in fuel economy and engine output (140 hp / 104 kW).

The 2014 Corolla also offers improved fuel economy due to its advanced Continuously Variable Transmission. This CVTi-S (i for intelligent, S for shift), which will be available on the LE, S, and LE Eco Corolla models, features several enhancements to improve its efficiency and driving performance with discrete shift points that help create a sensation more similar to a traditional hydraulic automatic transmission.

While the efficiency and reduced weight inherent in a pulley-type CVT would seem an ideal solution for vehicles emphasizing fuel efficiency, the characteristic CVT “rubber band” driving sensation of the engine winding to its power band upon acceleration has earned detractors.

With Corolla’s new CVTi-S, Toyota’s engineers improved the drivability of the new Corolla by adapting discrete stepped “gears” or shift points, into the car’s acceleration and deceleration curves. The Corolla’s new CVTi-S even mimics the familiar characteristics of hydraulic automatics creating a sense of positive shift engagement. On the Corolla S trim, up to seven shift-points can also be manually actuated from the shift gate or steering wheel paddle shifters.

As the first pulley-style CVT product offered by Toyota in North America, the engineering effort prioritized making the new CVTi-S’ operation and power application more appealing and familiar to North American drivers. Corolla’s engineers maximized the fuel saving design inherent in a pulley CVT while enhancing its operation to provide a more “direct feel” to pedal inputs through careful analysis of traditional automatic transmission operation. The new CVTi-S will provide a more linear connection between pedal effort and acceleration feel compared to previous CVT designs.

Toyota engineers addressed challenges presented by typical CVT design such as the high level of hydraulic pressure CVT’s require for operation, and the optimization of the pulley ratio range to offer the best performance and fuel economy.

Typically, CVT hydraulic-fluid pumps are driven at the same rate as engine speed; as a result, the pump wastes considerable effort, hurting transmission efficiency at higher engine speeds as the pump moves more fluid than necessary to lubricate and sandwich the CVT’s belt. With this new CVTi-S, hydraulic pressure was reduced to an optimal point to protect against belt slippage, while conserving drive effort to limit excess pumping losses.

The Corolla’s new CVTi-S is fitted with an oil pump that features a coaxial 2-port design that enables a 25% reduction in pump drive torque compared to other pump designs, and results in a greater efficiency with its reduction in parasitic engine loss.

Corolla_CVT
The Corolla’s new CVT maximizes the difference between the pulley sizes without an increase in the size of exterior case to achieve a speed ratio range of 6.3, which helps both fuel efficiency and acceleration. Click to enlarge.

For a belt-driven CVT, the range of speed ratios is determined by the diameters of the input and output pulleys. The greater the disparity in size between these two pulleys, the greater the range of gear ratios, efficiency and performance the transmission can offer. The clearances within the Corolla’s CVTi-S exterior casing and between internal components have been enhanced to better accommodate the most optimally sized pulleys within the compact transmission case.

The CVTi-S offers a forward gear ratio range of 0.396 to 2.480, which works well for acceleration, cruising speeds, and fuel-conscious driving with a 4.761 final drive ratio. The new CVTi-S includes a transmission fluid warmer is used to help get fluid to optimal temperature faster.

The Corolla’s new CVTi-S is uses a lower viscosity CVT fluid that protects all of the transmission’s internal parts while helping reduce parasitic loss to enhance efficiency and performance. The CVTi-S also offers extremely quiet operation from a compact, lightweight case design that adds reinforcing ribs and an optimal shape to help suppress vibration and noise.

Corolla models equipped with CVTi-S offer the capability of either an ECO or SPORT driving mode. On the Corolla LE Eco, the ECO driving mode makes accelerator control become non-linear to suppress the vehicle’s response to choppy driving and contain acceleration from standing start to help reduce fuel consumption. The accelerator pedal’s communication is the same as Normal-mode after 50% throttle. In ECO mode, the air conditioning operation is controlled in the interest of efficiency with compressor power reduced, the utilization of recirculation mode, and extra time allowed to attain a desired interior cabin temperature.

As equipped on the Corolla S, the new CVTi-S offers a SPORT mode that helps deliver a more dynamic driving experience with software tuning that alters shift points, creating transmission behavior during acceleration that enhances the sporty character of the S-grade. SPORT mode is not a track-focused mode, but rather a transmission setting that, along with unique electric power steering programming, helps create a sportier driving sensation during normal road and freeway driving.

On the Corolla S equipped with CVTi-S, steering wheel mounted paddle shifters allow drivers to make fast, sequential, stepped shifts through “7-speeds” to help enhance the driving experience. The Corolla S console shifter also offers a manual gate (M-position) that also allows drivers to make brisk upshifts or downshifts using the shift lever. The next shift step will automatically be engaged if the engine revolutions become high enough or down shifted if they become low enough. The M mode activity is displayed in the black and white display of the Corolla S combination meter. The Corolla’s Sport mode was developed and evaluated on roads within the key global markets to help ensure a more energetic drive across a broad range of conditions.

The base model Corolla L is offered with a four-speed automatic transmission or a six-speed manual transmission. The six-speed manual is also available in the Corolla S.

June 7, 2013 in Engines, Fuel Efficiency, Transmissions | Permalink | Comments (5) | TrackBack (0)

TrackBack

TrackBack URL for this entry:
http://www.typepad.com/services/trackback/6a00d8341c4fbe53ef01910310cea8970c

Listed below are links to weblogs that reference New 2014 Toyota Corolla brings Valvematic, new CVT to North America; up to >40 mpg highway:

Comments

The problem with belt-type CVTs is that they need to maintain clamping pressure on the belt while moving large volumes of fluid in the pulley cylinders during shifts.  This results in large parasitic power losses (power = pressure * volume/time).  A variable-displacement pump can reduce the losses during constant-ratio operation, but shifts (particularly downshifts at max engine torque) are always going to be an issue.

Still no direct injection or down-sized engine with a turbo-charger. Also no active aero elements. In fact it's supposed to be getting bigger than the outgoing model and yet it is still gaining 5 MPG from one model year to the next!
Most of the competition has already used the technology tricks to get to 40 MPG or a little over. Toyota seems to be holding back for the mid-cycle refresh or the next generation possibly. What that means is that there's still another 10-20% improvement possible in fuel economy as those technologies get integrated. Like Mazda's Skyactiv though they must be brought in as symbiotic features. For instance to get the most from direct injection you'd also increase compression ratio, upgrade the ECU and control EGR better in addition to making the bottom end stronger, coat the piston skirts and tops, etc. This would boost the economy to approximately 45 MPG with no down-sizing.

Other opportunities ripe for improvement would be to trim wheel weight, add start/stop and possibly an integrated starter/generator capable of delivering power back to the crankshaft. This would come with down-sizing to make the engine feel bigger off the line by delivering extra torque at low engine speeds. City mileage would improve by ~5 MPG. However now you're talking a $25k vehicle instead of a $17k-$20k base price.
The value of the Corolla primarily comes from the understanding that it will provide reliable transportation lasting for 30 years and will therefore carry an excellent re-sale value and low depreciation compared to the competition. If Toyota were to mess with that formula by increasing the price by adding technologies that are less reliable than currently used ones it would do so only at its own peril or to meet regulations.

It is my engineering opinion that the CVT is an outdated idea. It is probably a cheap solution for Toyota to build and it does offer increased engine efficiency over a 4 speed transmission. However, it is a friction based device so it constantly slipping and constantly wearing. It is probably not a cheap solution for the customer to own. A dual clutch 7 or 8 speed would be more efficient and they.would not need to provide the false feel of a multi-speed transmission.

GM looked at building a similar CVT back in the early 80's but wisely decided not to pursue it. At the time, I was working for the machine tool company that built most the machining lines for automotive transmissions so I got to see many of concepts that were being considered.

Wow, a 4 speed auto in the base model, and an "Eco" model that barely equals 20 or so other models in its class.

Toyota can do exceptional things when they set their minds to it, but they also do mediocre things.

Many Toyota's are getting outdated and will be overtaken by various Hyundai's, Honda's models (and many others) unless Toyota hires new designers and drops their outdated 4-speed transmission etc?

This may be the price to pay to have 6 out of 10 top sellers for 10+ years.

Verify your Comment

Previewing your Comment

This is only a preview. Your comment has not yet been posted.

Working...
Your comment could not be posted. Error type:
Your comment has been posted. Post another comment

The letters and numbers you entered did not match the image. Please try again.

As a final step before posting your comment, enter the letters and numbers you see in the image below. This prevents automated programs from posting comments.

Having trouble reading this image? View an alternate.

Working...

Post a comment

Green Car Congress © 2014 BioAge Group, LLC. All Rights Reserved. | Home | BioAge Group