CVT - Continuously Variable Transmission

A continuously variable transmission, or CVT, is a type of automatic transmission that provides more useable power, better fuel economy and a smoother driving experience than a traditional automatic.

Driving a car with a CVT

The controls for a CVT are the same as an automatic: No clutch pedal and a P-R-N-D-L-style shift pattern. But while an automatic transmission has a set number of gear ratios (a.k.a. speeds), usually 4, 5 or 6, the CVT can constantly change the relationship of engine speed to car speed. When driving a car with a CVT, you never hear or feel the transmission shift -- it simply raises and lowers the engine speed as needed, calling up higher engine speeds (or RPMs) for better acceleration and lower RPMs for better fuel economy while cruising.
Many people find the CVT disconcerting at first because of the way cars with CVTs sound. When you step on the accelerator, the engine races as it would with a slipping clutch or a failing automatic transmission. This is normal -- the CVT is adjusting the engine speed to provide optimal power for acceleration.


How it works

Traditional transmissions use a gearset that provides a given number of ratios (or speeds). The transmission (or the driver) shifts gears to provide the most appropriate ratio for a given situation: Lowest gears for starting out, middle gears for acceleration and passing, and higher gears for fuel-efficient cruising.
Though there are several types of CVTs, most cars use a pair of variable-diameter pulleys, each shaped like a pair of opposing cones, with a metal belt or chain running between them. One pulley is connected to the engine (input shaft), the other to the drive wheels (output shaft). The halves of each pulley are moveable; as the pulley halves come closer together the belt is forced to ride higher on the pulley, effectively making the pulley's diameter larger. Changing the diameter of the pulleys varies the transmission's ratio (the number of times the output shaft revolves for revolution of the engine), in the same way that a 10-speed bike routes the chain over larger or smaller gears to change the ratio. Making the input pulley smaller and the output pulley larger gives a low ratio (a large number of engine revolutions producing a small number of output revolutions) for better low-speed acceleration. As the car accelerates, the pulleys vary their diameter to lower the engine speed as car speed rises. This is the same thing a conventional automatic or manual transmission does, but while a conventional transmission changes the ratio in stages by shifting gears, the CVT continuously varies the ratio -- hence the name "continuously variable transmission".


Advantages of the CVT

Engines do not develop constant power at all speeds; they have specific speeds where torque (pulling power), horsepower (speed power) and fuel efficiency are at their highest levels. Because there are no gears to tie a given road speed directly to a given engine speed, the CVT can vary the engine speed as needed to access maximum power as well as maximum fuel efficiency. This allows the CVT to provide quicker acceleration than a conventional automatic or manual transmission while delivering superior fuel economy.


Disadvantages of the CVT

The CVT's biggest problem has been user acceptance. Because the CVT allows the engine to rev at any speed, the noises coming from under the hood sound odd to ears accustomed to conventional manual and automatic transmissions. The gradual changes in engine note sound like a sliding transmission or a slipping clutch -- signs of trouble with a conventional transmission, but perfectly normal for a CVT. Flooring an automatic car brings a lurch and a sudden burst of power, whereas CVTs provide a smooth, rapid increase to maximum power. To some drivers this makes the car feel slower, when in fact a CVT will generally out-accelerate an automatic.
Automakers have gone to great lengths to make the CVT feel more like a conventional transmission. Most CVTs are set up to creep forward when the driver takes his or her foot off the brake. This provides a similar feel to a conventional automatic, and serves as an indicator that the car is in gear. Other CVTs offer a "manual" mode that simulates manual gear changes.

Because early automotive CVTs were limited as to how much horsepower they could handle, there has been some concern about the long-term reliability of the CVT. Advanced technology has made the CVT much more robust. Nissan has more than a million CVTs in service around the world and uses them in powerful cars such as the 255 horsepower Maxima, and says their long-term reliability is comparable to conventional transmissions.


History of the CVT

Leonardo DaVinci sketched the first CVT in 1490. Dutch automaker DAF first started using CVTs in their cars in the late 1950s; however technology limitations made CVTs unsuitable for engines with more than around 100 horsepower. In the late 80s and early 90s, Subaru offered a CVT in their Justy mini-car, while Honda used one in the high-mileage Honda Civic HX of the late 90s.
Improved CVTs capable of handling more powerful engines were developed in the late 90s and 2000s, and CVTs can now be found in cars from Nissan, Audi, Honda, Ford, GM, and other automakers.

Honda Airwave

TOKYO, Japan, April 7, 2005 - Honda Motor Co., Ltd. today announced the debut of the Airwave*, an all-new 1.5-liter compact station wagon that boasts top-of-class*1 luggage capacity, the practical utility of versatile seating arrangements in a compact body, along with an extra-large glass "Sky Roof"*2 that conveys an exhilarating open-air feeling. The new Airwave will go on sale April 8, 2005, at Honda automobile dealers throughout Japan.

The Airwave was designed around the "new wave compact" concept - a new idea for compact cars that function as a cool lifestyle component for youthful customers who value their own individual sensibilities over any single style.

In order to achieve both a roomy passenger interior and a luggage compartment that boasts top-of-class storage capacity, Airwave incorporates Honda's original center-fuel tank layout. In combination with the convenience of a low-floor design, this also allows a variety of seating arrangements. The Sky Roof, with its extra-large opening, delivers an open-air feeling, while the ample glass area that extends seamlessly from the front windshield up onto the roof adds to the exterior stylishness.

The Airwave is equipped with a 1.5-liter VTEC engine that provides ample power for a fun, exciting drive. In combination with the Honda Multimatic S transmission, it delivers smooth acceleration with high torque and high output performance at mid to high speeds, combined with top-of-class*1 fuel economy of 18.0km/l*3. All Airwave trim levels exceed Japanese government fuel economy standards for 2010 by 5% and have earned Japanese Ministry of Land, Infrastructure and Transport certification as Low-Emissions Vehicles, with emission levels 75% lower than those required by 2005 standards, making them eligible for preferential Green Tax measures.

* The name Airwave suggests flowing air or wind and was chosen to describe this refreshing, invigorating vehicle with refined styling, and a bright, spacious interior with an open-air experience that promotes a feeling of oneness with nature.
*1 1.5-liter station wagon class
*2 Window glass is fixed in position; available on G Sky Roof and L Sky Roof types.
*3 FF vehicle. Fuel consumption in 10-15 mode (Japanese Ministry of Land, Infrastructure and Transport calculations)



Key Features

< Packaging and utility >
The center-tank layout, which positions the fuel tank under the front seat, results in a low, flat floor and versatile seating arrangements, creating a spacious passenger interior and luggage compartment.
The easy-to-operate ULTR seats feature four seating arrangement modes:

- Utility Mode
The 6:4 split rear seats are equipped with a dive-down mechanism that enables changeovers to a 1,810mm*410 flat, low-floor luggage compartment with one quick operation�no need to remove the headrests.

- Long Mode
In addition to Utility Mode, the front passenger seat fully reclines to create enough space for items as long as 2,700mm*10.

- Tall Mode
The rear seat cushions tip up to create another cargo space 1,250mm*5 high�enough space to get changed in.

- Refresh Mode
Removing the front headrests and fully reclining the seat backs creates enough room to stretch one's legs out and relax. During breaks from driving, occupants can lie back in comfort and gaze at the scenery through the Sky Roof.

Full consideration was given to rear-seat comfort as well, with a top-of-class tandem distance*6 of 985mm*7 that creates a spacious passenger environment.
The low floor made possible by the center-tank layout results in a luggage room height of just 520mm*8*10above the ground, making it easier to load and unload luggage. At the same time, the low floor secures a top-of-class maximum luggage room capacity of 473 liters*9.

*4 With two passengers and the front seats set to their rearmost position
*5 G and L types; for G Sky Roof and L Sky Roof types, 1,230mm
*6 Distance between the front and rear seat hip points
*7 Honda measurement based on seating position of an average Japanese male (as determined by Honda)
*8 For FF vehicle; or 4WD vehicle is 535mm
*9 With five vehicle occupants; Honda measurement according to VDA formula
*10 Honda in-house measurements


< Design >
Interior design

The "airy cabin" design concept provides a comfortable space that makes occupants feel as if they are riding on air, with an exhilarating feel of liberation. The expansive glass Sky Roof creates a liberated feel any time, anywhere, regardless of the climate or season.
The 1,110mm long*11 by 770mm wide*11 large-aperture Sky Roof combines privacy glass to cut out bright light and high-thermal-absorbing UV-cut glass with outstanding insulating properties to fully protect occupants from ultraviolet radiation and the sun's heat. Also, an electric sunshade opens and closes in three stages with the press of a switch, to allow occupants to adjust the size of the opening.
The front seats are formed to naturally and deeply embrace the lumbar area, with a softer middle portion and firmer sides for the right combination of soft comfort and firm support. In the rear, full consideration has been given to cushion thickness and seatback height, to combine comfort a step above the rest with the functionality of the ULTR seats' versatile seating arrangements.
The instrument panel was designed on the motif of a bird with outspread wings, creating a relaxing image of two layers of overlapping wings. At the same time, the 2-tone color wing-line flows out to the sides to achieve a rounded overall design that imparts feelings of both liberation and security.
The speedometer, tachometer, fuel gauge, temperature gauge, and 7-speed mode*12 shift indicator are laid out as five independent, self-illuminating meters. The meters employ a cylinder-type design patterned after the exhaust ducts of a rocket or jet engine, to heighten the interior's sporty atmosphere.
The interior is available in two color schemes: one features Black & Bright Titanium two-tone coloring, with Black above and Bright Titanium below, while the other is a sporty Black monotone. The two color schemes can be freely combined with the eight body colors.

*11 Internal dimensions, according to Honda in-house measurements
*12 Available on L and L Sky Roof types

Exterior design
Created under a "smart, dynamic" design concept, the Airwave's exterior presents a carefree form for stylish urban cruising. The Sky Roof creates a continuous glass area from the windshield to the roof for a glassy effect that gives occupants a beautiful view of the sky above.
For the front view, the bumper flows smoothly into the sides of the vehicle to create a rounded look, while the bold, chrome-plated front grill adds a feeling of girth.
The rear view presents the same feeling of girth as the front view, while the rear quarter glass draws it together to create a sporty silhouette with a stable feel.
For the side view, a deeply sculpted character line produces an effective wedge shape, for a taut yet substantial feel expressive of dynamic motion.
Eight body colors are available, including one new color: Chiffon Green Metallic.
< Performance >
Engine and transmission
The 1.5-liter VTEC engine delivers a sophisticated balance of performance and environmental friendliness, with pleasing, smooth acceleration right up to the high-rev range, and top-of-class fuel economy of 18.0km/l.
1.5-liter VTEC engine
Maximum output: 81kW (110PS)
Maximum torque: 143N-m (14.6kg-m)*13
The Airwave is equipped with a Honda Multimatic S continuously variable automatic transmission, to respond to a wide variety of situations, from city driving to outdoor leisure activities. To further add to the fun of the drive, the L and L Sky Roof types are also equipped with 7-speed mode so the driver can enjoy a manual shift feel, along with a shift indicator that displays gear changes made using the paddle shifters.
Lightweight, compact, real-time 4-wheel drive is also available on all types.
*13 Net values



< Chassis >
The suspension employs a new design with struts in the front and a rear suspension with an H-Type torsion beam-based layout. Compliant responsiveness and stable cornering are achieved through roll center height adjustment and optimized roll steer to create a relaxed, stable ride that feels comfortable and secure for all vehicle occupants.
The brake system delivers reliable stopping power even when the car is weighted down with luggage. Fourteen-inch ventilated front discs are combined with 7+8-inch tandem master power cylinders that deliver a lighter pedal touch and powerful braking along with superior space efficiency.
Quietness measures include sound-absorbing sound insulation materials efficiently positioned to cut down on road noise despite layout limitations due to the low floor, while engine mounts have been made more rigid to produce a quiet yet pleasing engine sound.
In order to incorporate the sky roof and the largest tailgate in its class (1,130mm wide by 855mm high opening)*10 without sacrificing body rigidity, closed cross-section frames are employed around the entire circumference of each opening. Reinforcing materials have been added to a Monaca-style core with overlapping front and rear sections to achieve strength and rigidity without a thicker cross-section.


< Safety Performance >
ABS with EBD (Electronic Brake-force Distribution) and brake assist (which augments pedal pressure) are standard on all types, along with a high-mount LED rear brake light that heightens recognition for the drivers of vehicles to the rear.
Honda's original G-CON (G-force Control) technology is incorporated to create a body with a crash safety design that can withstand a 55km/h full-frontal collision, a 64km/h front offset collision, 55km/h side collision, and a 50km/h rear collision. To further improve safety in real-world collisions, Honda has implemented its own vehicle-to-vehicle collision testing program*14 with its own independently established standards. This collision testing is much more demanding than conventional tests, in which the car is crashed into a fixed barrier. The safety design of the Airwave meets even these stringent testing requirements.
All types are equipped with 3-point, pretensioner ELR seatbelts with load limiters and lap pretensioners for both front seats. All of the back seats, including the center seat, are equipped with 3-point ELR/ALR (child seat restraint mechanism) seatbelts and headrests, to secure a high level of safety in the rear seats as well.
The pedestrian injury reduction body features a hood, front bumper, and other parts designed to absorb impact to a pedestrian's head and lower limbs in the event of an accident, reducing injury severity. The design has earned Japanese Ministry of Land, Infrastructure and Transport certification as conforming to government pedestrian head protection standards*15 scheduled to take effect in September 2005.
ISO FIX-compatible child seat anchoring bars and tether anchors for quick, reliable child seat installation are standard equipment on the left and right rear seats for all types.

*14 Testing involves a 50% front offset collision with a 2-ton class passenger car, and both vehicles traveling at 50km/h.
*15 Standards regulate vehicle hood impact mitigation performance to help protect pedestrians' heads in the event of a collision.



< Environmental performance >
A modified exhaust manifold shape for more rapid heating of the catalytic converter, repositioning of the O2 sensor for improved sensing performance, and other measures result in fewer exhaust gas pollutants. All types have been certified by the Japanese Ministry of Land, Infrastructure and Transport as having emissions levels 75% lower than those required by 2005 standards.
Fuel economy has been enhanced through such measures as optimized engine ignition timing and smoother cam journal surfaces for reduced friction. All types exceed Japanese government fuel economy standards for 2010 by 5%.
Use of lead has been reduced to less than 10% of 1996 levels.
Use of hexavalent chromium plating has been reduced, with its complete elimination as the ultimate goal. Its use has already been eliminated on fuel filler pipes, brackets, and other components.
Polyvinyl chloride (PVC) has been greatly reduced from interior and exterior plastic components in favor of environment-friendly, highly recyclable materials. As a result, over 90%*16 recyclability has been achieved.

*16 According to independent Honda measurement standards