Today we have a new type of automatic transmission technology to consider when looking at new Nissans. It’s not a tweek on familiar old automatics but an entirely new type of technology. These new transmissions are called Continuously Variable Transmissions or CVTs. And they aren’t all that new. Nissan started putting CVTs into their automobiles back in 2002 and today they are included in much of the Nissan model lineup. Some drivers love them because they offer some advantages over standard and automatic transmissions. They can offer more useable power, better fuel economy and smoother driving. Here’s how they work:
Conventional automatic transmissions use sets of gears inside their housings that provide different ratios or speeds. Electronic transmission control units sense the vehicle’s speed and load and shift the transmission’s gears automatically to provide the most appropriate ratio. Lowest gears are selected for low speeds, middle gears for acceleration, and higher gears for thrifty cruising.
They are simple too. A CVT replaces the complex gears common in standard and automatic transmissions with two large variable-diameter pulleys with a metal belt running between them. The way it works is that during operation the pulleys move in and out such that the drive belt between moves higher on one pulley, lower on the other providing a “continuous” numerical gear reduction. You can picture this roughly as the way a 10-speed bike works. By routing the chain over smaller or larger gears, you can easily change the gear ratios on the fly.
The controls for a CVT-based car are the same as an automatic-based car: Two pedals (gas and brake) and a P-R-N-D-L-style shift pattern. When driving a car with a CVT, you won’t hear or feel the transmission shift as it moves from one gear to the next, though. 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. Because a CVT can theoretically adjust to any gear ratio, engineers can program it to give maximum performance during all driving situations.
The CVT’s biggest problem has been user acceptance. Because the CVT allows the engine to rotate at any speed, the noises coming from under the hood can sound odd to those accustomed to conventional automatic transmissions. The gradual changes in engine note sound like something is “slipping”– signs of trouble in a conventional transmission, but perfectly normal for a CVT. This has resulted in automakers going to great lengths to make CVTs feel more a little more like conventional transmissions.
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. This has not proven to be a problem, though. Advanced technology has made the CVT quite robust and reliable. Today, Nissan has more than a million CVTs in service around the world and their long-term reliability has been excellent.
Source: Team Nissan