Driving up on winding roads sometimes become a tough task when there is a decent amount of traffic and you have manual shift gearbox on your car. None of the gears seems perfect when vehicle is fully or even partially loaded on such roads. Some gear ratios are too high and some gear ratios are too low for such driving up conditions. But it will be totally different story when you have continuously variable transmission (CVT)
As the name suggests, its a continuous variable transmission and doesn’t have fixed points of shifting like manual transmission. The benefit is a smooth drive and constant power and better fuel efficiency. Since the engine runs at it’s most efficient operating point, even in stop-go traffic CVT gives 7% better fuel efficiency than manual transmission. In addition to this, CVT assembly is very compact owing to a very few components in the whole system. The compactness has two advantages, few parts implies less manufacturing cost and other being that it can be fitted even in the smallest entry level vehicles where there is very less space in engine bay. CVT can operate in wide range of power and torque and therefore it is practical to use in real life. CVTs are very popular in Japan, China and North America being the next major markets.
CVT is a closely assembled set of pulleys on which flexible belts work as a bicycle chain. Two lobes of such set of pulleys mounted on shafts kept on the opposite side, one is driving shaft and other is driven shift. When transmission ratio is higher the driving shaft slides the belt on the higher side of pulley and driven shaft selects the lower side. The positions are reversed when there is a need for lower gear. On drive and driven shafts the belt moves between two cones and these cones are placed opposite to each other. The shifting of driving, driven pulleys and belt according to vehicle needs is seamless and therefore constant power is always an output in case of CVTs. In manual transmission there is always a power loss between two gear, no matter how fast you shift. CVT always give constant power and it is seamless. There is an optimum balance in power and torque with CVT transmission.
The new developments in CVT technology allows full controlling of operation of CVT via ECU. The ECU sets the engine at optimum speed thereby achieving seamless power with better fuel efficiency. This compact transmission is a choice for car buyers in Japan and CVT is finding its growth in upcoming markets like China and North America. The CVT technology is currently offered in 300 production vehicles and is expected to grow in next 3 years. In India Nissan Sunny CVT delivers 20% more fuel economy than its petrol variant just because of few advantages discussed above.
Photo and video Credit: Bosch