What do you know about transmissions?

I am sure you are familiar with some of the acronyms the auto industry uses like; Anti-lock brakes (ABS), electronic stability control (ESP), gasoline direct injection (GDI): There is a fairly new one called CVT. (continuous variable transmission)

The (CVT) transmission was designed to reduce cost and is less complicated and is designed to give better fuel economy.

Does  every car use a CVT transmission?

Let's take a look at transmission details and then we will answer the question "Does every car use a CVT transmission?'

Do you know how a transmission works?

A transmission transmits power from the engine to the wheels. An engine cannot be directly linked to the drive wheels, therefore we must transform the power of the engine to the wheels. This is what a transmission does.

Most passenger cars use a gear type of transmission with a range of speeds from 2 to 9. Each “speed” is a different gear ratio utilizing gear sizes. The size of the gears relative to each other utilizes  the power of the engine to give the car the ability to start from a dead stop and reach very high speeds.

A small gear turning a big gear has a lot of mechanical advantage but must turn faster than the big gear to maintain a speed. A big gear turning a small gear has less mechanical advantage, but it gets to turn slower to maintain the same speed. That’s a conventional transmission. The ratio of the transmission – its flexibility – is always limited by the number of speeds.

CVT: It is a gearless gearbox:

A CVT takes this basic idea and adapts it to cars but with even greater flexibility.

Most CVTs have two pulleys wrapped by a single belt with a V-shaped cross-section (there are other kinds but we will explain one method. This will give you an idea of the difference between CVT and conventional gear transmissions. Each pulley looks like a yo-yo and is actually made up of two cones that face each other. Under the force of hydraulic pressure, the cones either come together or separate, causing the V-shaped belt to either ride higher in the pulley groove or lower down and closer to the center, very similar to your bicycle shifting patterns.

As you drive, the two pulleys variously squeeze in or separate to change the ratio between the input pulley (from the engine) and the output pulley (to the wheels).

When you start from a stop, the control computer un-clamps the input pulley so the belt turns the smallest diameter while the output pulley (which goes to the wheels) clamps tighter to make the belt turn its largest diameter. This produces the lowest gear ratio for the quickest acceleration. As speed builds, the computer varies the pulley diameters, for the best balance of fuel economy and power.

As a result, instead of five or six ratios, you get an infinite number of ratios between the lowest (smallest-diameter pulley setting) and highest (largest-diameter pulley setting).


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