Continuously variable transmission

A transmission that changes the ratio between input and output speeds continuously rather than selecting from fixed gear steps. It lets an engine operate across a range of speeds without discrete shifts.

Variable-diameter pulley: A pulley whose effective working diameter changes as its movable faces shift. Paired pulleys change their effective diameters in opposite directions to vary the transmission ratio.
Automobile: A road vehicle, usually with four wheels, powered by an engine or electric motor. Automotive CVTs trade discrete shifts for continuous ratio control during acceleration.
Manual transmission: A transmission whose driver selects among discrete gear ratios, typically using a clutch and gear lever. Its fixed steps make the difference from continuously variable ratio selection explicit.
Engine speed: The rate at which an engine's rotating shaft completes revolutions, usually measured in revolutions per minute. A CVT can hold engine speed near a chosen operating point while vehicle speed changes.
Belt drive: A power-transmission system that transfers rotation between pulleys using a flexible belt. Many automotive CVTs use a metal belt to transfer torque between variable-diameter pulleys.
Snowmobile: A motorized vehicle designed to travel over snow using skis and a driven track. Many snowmobiles use CVTs to match engine speed to changing load and track speed.
Automatic transmission: A transmission that selects gear ratios automatically, commonly through planetary gearsets. Conventional automatics shift among fixed ratios, even when the driver does not select them.
Fuel efficiency: The amount of useful travel or work obtained from a quantity of fuel. Keeping an engine near efficient operating conditions can improve fuel economy in suitable vehicles.
Toroidal continuously variable transmission: A CVT that transfers power between toroidal discs through tilting rollers. It varies ratio through roller position rather than changing pulley diameters.
Scooter: A small motor vehicle, commonly with a step-through frame and compact wheels. Many scooters use compact belt CVTs for automatic speed variation.

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