Exact(17)
The pulleys expand and contract in opposite directions, causing the belt to ride closer or farther from the center, varying the drive ratio over a wide range.
While some early cars could be operated with more than one drive ratio, they could not be shifted while moving.
A somewhat stout 3.16:1 final drive ratio is said to provide a balance of responsive acceleration and economical low-r.p.m. cruising.
Leaving the starting line with a direct drive ratio of 3.25:1, the car's overdrive planetary transmission reduces the ratio to 2.25:1 when Mr. Adamowicz pushes a button.
The C.V.T. does not have conventional fixed gear ratios, instead using a belt and pulley system to constantly vary the drive ratio according to the demands of your right foot.
Indeed, I would wager that a regular gas-engine Tahoe or Yukon with a 3.08 final drive ratio and a six-speed automatic transmission (instead of the usual four-speed) might well match the highway fuel economy of the hybrid versions.
Similar(43)
Like most scooters, the Vespa uses a continuously variable transmission, or C.V.T., a design that automatically adjusts the internal drive ratios according to the demands of the moment.
Inventors as far back as Leonardo da Vinci have been attracted to the C.V.T. idea and have come up with several ways to achieve the same goal of juggling drive ratios in a seamless fashion.
But before long it became clear that building vehicles capable of both brisk acceleration and respectable top speeds would require some method of changing the speed relationships — the drive ratios — to match the conditions of the moment.
Another important change is the choice of a 3.08 final-drive ratio, compared with the 3.73 ratio in conventional Tahoes and Yukons.
The final-drive ratio is also taller than in the regular Cruzes, but such efficient gearing damps acceleration.
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