Over the last several years, many manufacturers have been offering a new type of transmission technology in their vehicles. Technically it’s an “automatic” but not the familiar old automatic; it’s called a CVT (continuously variable transmission). CVTs are similar to automatic transmissions when you drive them but operate on an entirely different principle “under the hood.” Here are the details:
Conventional automatic transmissions use multiple sets of gears that provide different gear ratios or speeds. As the number of gear ratios increase (as they have been recently for fuel economy reasons), automatic transmission can become quite complex. Enter the CVT.
A CVT replaces the gear sets in automatic transmissions with two variable-diameter pulleys, each shaped like a pair of opposing cones, with a metal belt running between them. The way they work is that during operation the pulleys move in and out such that a drive belt between moves higher on one pulley and lower on the other. The result of this movement is 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 to change the gear ratios. It’s a very simple principle.
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.
The CVT’s biggest problem has been user acceptance. Because the CVT allows the engine to rotate at a wide range of speeds, the noises coming from under the hood can sound odd to ears accustomed to conventional automatic transmissions. The gradual changes in engine note may sound like something is “slipping.” For user acceptance reasons, automakers have been going to great lengths to make their CVTs feel more like a an conventional automatic transmission.
The future of the CVT remains to be seen. In spite of the obvious efficiencies of CVTs, customers can be fickle and may prefer an older technology. We will likely see how CVT transmissions fare over the next few years or so. Personally, we bet that CVTs are here to stay.
Source: Ken Garff West Valley Used Cars
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