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Advanced Transmission System


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1. Continuously Variable Transmission (CVT) 2. Drive Systems
3. Double Clutch - Transmission System

Advanced Transmission System Rating  :      

Leonardo DaVinci sketched the first CVT in 1490 and who would have thought that after 500 years it would become a rage in the world of automobiles. 

CVT’s or Continuously Variable Transmission are advanced version of automatic transmission. The controls for a CVT are the same as an automatic: Two pedals (no clutch) and a P-R-N-D-L-style shift pattern. But while an automatic transmission has a set number of gear ratios (speeds), usually 4, 5 or 6, the CVT can constantly change the relationship of engine speed to car speed. When driving a car with a CVT, you never hear or feel the transmission shift -- 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 while cruising.

Unlike automatic transmission CVT’s do not use planetary form of gears nor do they have fixed number of gear ratios. The word "gear" however, still appears in the explanation of a CVT, simple because broadly speaking; a gear refers to a ratio of engine shaft speed to drive shaft speed. Even though CVTs change this ratio without using a set of planetary gears, since they still affect shaft speed and drive speed, they are, for the sake of convenience and easy understanding described as having low and high "gears" . 

Transmission systems key role is to change the speed ratio between the engine and the wheels of an automobile. Cars without a transmission would have only one gear; imagine a car which has only the first gear, such a car would definitely have great initial pick-up (Torque) power from standstill, however it would soon run out of speed and if on the other hand a car had only 3rd gear it will almost have zero ability to accelerate from standstill, whilst it would be quite powerful as higher speeds or once the car is in motion.

Transmissions uses a range of gears - from low to high - to make more effective use of the engine's torque with changing driving conditions. These gears can be engaged manually or automatically.

Gears in a traditional automatic transmission, the gears are interlocking, toothed wheels that help transmit and modify rotary motion and torque. A combination of such gears creates multiple gear ratios these typically are; four forward and one reverse gear. However the driver experiences shift shocks when these type of transmission cycles through its gears.

CVT’S Basics

Unlike traditional automatic transmissions, continuously variable transmissions don't have a gearbox with a set number of gears, which means they don't have interlocking toothed wheels. 

Though there are several types of CVTs, most cars use a pair of variable-diameter pulleys, each shaped like a pair of opposing cones, with a metal belt or chain running between them. One pulley is connected to the engine (input shaft), the other to the drive wheels (output shaft). The halves of each pulley are moveable; as the pulley halves come closer together the belt is forced to ride higher on the pulley, effectively making the pulley's diameter larger. Changing the diameter of the pulleys varies the transmission's ratio (the number of times the output shaft revolves for each revolution of the engine). Making the input pulley smaller and the output pulley larger gives a low ratio (a large number of engine revolutions producing a small number of output revolutions) for better low-speed acceleration. As the car accelerates, the pulleys vary their diameter to lower the engine speed as car speed rises. This is the same thing a conventional automatic or manual transmission does, but while a conventional transmission changes the ratio in stages by shifting gears, the CVT continuously varies the ratio -- hence its name. 

CVT’s are known for their higher fuel efficiencies as it enables the engine to run its most efficient revolutions per minute (RPM) over a range of vehicle speeds. CVT’s maximise vehicle performance as it allows the vehicle engines to turn at RPM’s which are close to vehicles peak power delivery point. 

CVT ADVANTAGES

Advantages of CVTs
Feature
Benefit
Constant, stepless acceleration from a complete stop to cruising speed
Eliminates "shift shock" -- makes for a smoother ride
Works to keep the car in its optimum power range regardless of how fast the car is traveling
Responds better to changing conditions, such as changes in throttle and speed
Eliminates gear hunting as a car decelerates, especially going up a hill
Less power loss in a CVT than a typical automatic transmission
Better acceleration
Better control of a gasoline engine's speed range
Better control over emissions
Can incorporate automated versions of mechanical clutches
Replace inefficient fluid torque converters
 
A CVT Test Drive Simulation
When you accelerate a car with a continuously variable transmission, the engine revs up toward its  peak power RPM and stays there, however the car doesn't react immediately, transmission kicks in a moment later, accelerating the car slowly, steadily and without any shifts. 
Theoretically speaking a car with a CVT should reach 60 mph (100 km/hr) 25-percent faster than the same car with the same engine and a manual transmission.  That's because the CVT converts every point on the engine's operating curve to a corresponding point on its own operating curve.  
CVTs are equally efficient on hills. There is no "gear hunting," because the CVT cycles steplessly down to a gear ratio appropriate for the driving conditions. A conventional automatic transmission shifts back and forth trying to find the right gear, which is far less efficient.
 
 
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