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CVTs
CVTs are basically a device to engage or disengage the drive, with a very strong segmented steel belt connected between two pullys that have one of the pulley faces on each pully adjustable in realtion to the other. This allows both pulleys effective diameter to be adjusted in minute increments.
Years of development, especially by Nissan and Jatco (transmission manufacturer) in Japan have adressed many early issues with CVTs. They now use a "push belt" with around 400 segmented hardened steel "shoes" that are compressed against each other, and special fluids that provide lubrication while still allowing friction between the belt segments and the faces of the pulleys. The 2003 Nissan Murano was capable of towing 3500 pounds and the transmission could handle the torque and horsepower of the 3.5 liter engine providing a 3800 pound vehicle with acceleration of 0-60 in 8 seconds and 25 MPG highway. I have driven one at 70 MPH average speed, while fully loaded, and averaged 25 MPG.
In the latest model years, the most recent Nissan Sentra, Altima, and Versa model have recieved the latest versions of their CVTs and the Altima is rated at 38 MPG highway, while the Sentra and Versa are rated at 40, with the Versa rated at 35 combined, one of the highest non hybrid combined ratings of any comparable vehicle.
My personal experience with Nissan CVTs includes the Murano, Rogue, Sentra, and Altima. Their CVTs will provide you with good acceleration without the engine speed and load changing significantly, meaning you start off at 1800 RPM and the engine stays at 1800 RPM while the cars speed increases until it is going as fast as it will at 1800 RPM. In the first Murano we owned 1800 RPM was right at 70 MPH. More accelerator input increases the RPM speed which will still remain constant as long as the pedal pressure is constant.
Throttle by wire, combined with computer controlled CVTs means your gas pedal is actually an accelerator pedal that controls the drivers request for a rate of acceleration. The system compensates for minor fluctuations in pedal imput, as well as enhanced DFCO using thr CVTs wider ratios to keep the engine speed up during deceleration, but as low as possible to engage DFCO.
The torque converter on my 2008 Altima locked up at 12 MPH, basically it was used as a clutch and locked once the vehicle speed allowed the CVT pulleys to be used exclusively.
feel free to add any information that might be constructive.
regards
Mech
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