Text & Photos: Bhargav TS
The CVT manufacturer supplies the Xtronic gear box to Nissan Motor India and to other vehicle manufacturers across the globe; aims to increase market share in the coming years.
As vehicles increase and traffic becomes worse by the day, it’s tedious and stressful to drive a car in the city. To surmount this, Automated Manual Transmissions (AMT) have come in handy to drive without strain in all traffic conditions. However, in India, AMTs are not popular as there is a perception that it consumes more fuel when compared to the manual transmission. To match fuel efficiency in both types of transmission, Nissan Motor India has introduced the Xtronics – Continuously Variable Transmission (CVT) in its wide range of cars in India. These CVTs are manufactured by JATCO, a Nissan subsidiary and a global supplier of automatic transmissions and CVTs.
To know how JATCO achieves better fuel efficiency in their CVTs, Auto Components India spoke to Hiroki Sugiyama, General Manager – Sales, JATCO Ltd. He said, “We achieve better fuel efficiency in CVTs because here we use varying diameter pulleys and a belt to vary the drive ratio continuously. Which means the driver doesn’t need to shift through gears, and power is applied seamlessly through acceleration. The traditional transmission causes loss of power between gear changes and reduces the fuel efficiency during each gear change. In CVT the fuel efficiency is achieved because it produces continuous power and also has less weight. A CVT uses less moving parts so it weighs less than a traditional unit. It can reduce fuel consumption by as much as 7%, since the engine is constantly kept at its most efficient operating point.”
JATCO manufactures a wide range of CVTs suitable for mini cars and large cars up to 3,500cc capacity. The company claims that CVTs don’t have fixed gear ratios, so the car can be fairly used within that spread. According to market conditions gearboxes can be manufactured to cover the entire range from sporty cars to those which are fuel efficient. For individual drivers the drive behavior of the car is sensed; the CVT can be controlled to select the optimal shift pattern. This helps in easy adaptation and enhancing fuel efficiency.
The gearbox manufactured by JATCO has an electronic control unit that helps the optimal shift pattern, which in turn helps gain more fuel economy. Sugiyama explained, “We continuously reduce the friction loss by having less mechanical parts, so we get better fuel efficiency when compared to other transmissions. Currently, CVT is evolving faster especially in Japan and now it is penetrating more in the US, China, and the European market as well. When compared to our competitors, we focus more on advancement in CVT technology, so we try to have a much wider ratio to reduce the friction loss in the gear box.”
Like other continuously variable transmissions out there, the Nissan Xtronic CVT doesn’t use traditional fixed gear ratios. Instead, it relies on 2 hydraulically operated steel pulleys, where one pulley is connected to the engine output shaft and the other to the drive train, which are connected by a metal chain link. Once the accelerator pedal is pressed, the sides of the v-shaped pulleys either push together or pull apart to move the position of the chain on the pulleys. These are special pulleys since they can change their size and thus change the gearing in the vehicle. There are no set numbers of gears in a CVT because it can choose the exact gear ratio along a variable continuum between its lowest and highest gear ratios. Therefore, this gearbox can be easily used in both low and high speed conditions.
In a traditional transmission the engine speed drops between gear changes and as this happens the engine moves in and out of its peak power range, losing efficiency. Nissan first adopted the CVT in 1992 and over the last 22 years the gearbox has undergone several changes, now refined into a modern version that boasts of a 10% increase in fuel efficiency, accelerating faster while running quietly. It is also very flexible in terms of delivering customer requirements like power, comfort and fuel economy. The CVT realises those features demanded by customers and JATCO is making continuous improvements in terms of CVT technology.
JATCO started a manufacturing facility in Japan and now has expanded its footprint with facilities in Mexico, China and Thailand. In Mexico it has 2 plants, which have a combined capacity of 1.7 million units annually. In China it can produce 1 million units and in Thailand the company is expanding its capacity to 7 lakh from 5 lakh units per year.
CVTs are equally suitable for diesel, petrol, and the hybrid powertrain. And while this technology saves fuel in classic internal-combustion engines, it can also increase the hybrid powertrain’s electric drive range. This is because the CVT allows the internal-combustion engine to run at a higher speed, close to the optimum operating point. As a result, part of the energy released can be used for forward propulsion, while the rest can be stored in the rechargeable battery. “In Europe we started to use CVTs in diesel engines and the CVTs that we manufacture have high end-torque of 380 Nm. The same CVT can be used in the Indian market depending on the market demand,” concludes Sugiyama.
Micra CVT – a perfect city car?
The Micra is the first car with the latest generation CVT coupled to a small 1.2L petrol engine. Nissan has brought down frictional losses to minimise fuel consumption. The current generation uses far less transmission lubricant than the earlier ones, leading to 40% lower friction. The computed fuel efficiency increase is 15%. The effective transmission ratio is 7.3:1, a range broader than conventional ATs. The Nissan CVT comes with 2 modes of operation – the mileage-optimised ‘Normal’ mode, and the comparatively free spirited ‘Sports’ mode. The shift between the two on the fly, via a small button you press with the left thumb. Sports mode, when engaged, is indicated on the dash. The shifter is a simple P-R-N-D stick with a single “L” position to keep the belt in the ‘low gear’ range (for steep inclines, declines etc.).
The Micra CVT feels more suited to city driving rather than an outright highway run. When driven hard, the motor feels strained and gets loud enough for the engine noise to make its way into the cabin. The CVT takes time to respond to a jab of the throttle pedal, and this makes overtaking fast-moving cars quite tricky. Overtaking has to be well planned to execute, else the CVT will get you into trouble. And once you have lost momentum, it will take a couple of seconds before the CVT shifts down and starts building up the pace all over again. Overall, Micra CVT performs well in the city but it is not a highway cruiser. ACI
