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AMT, IMT, CVT, DCT — why you must know your automatic car before you buy one

Over 10% of all passenger cars sold in India had some form of automatic transmission or another. But all automatics are not created equal.

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The past few months are seeing car sales figures scale new highs, and Indians are buying cars equipped with various different features. Recently, Hyundai revealed that one in three cars they sold in the first half of 2022 came with a sunroof. But that same slide had another fascinating statistic: one in five Hyundai cars sold in India had an automatic transmission. In fact, over 10 per cent of all passenger cars sold in India had some form of automatic transmission or another.

But what do I mean by ‘some sort of automatic’? It is a common misconception that all automatic transmissions are the same. It is a veritable alphabet soup of acronyms for different sorts of automatic transmissions. While all ‘automatic’ transmissions remove the need to physically operate the clutch pedal, there is still a clutch in the vehicle. Sort of, anyway. The traditional ‘torque converter’ automatic has a ‘wet clutch’ and the dual-clutch has, as its name suggests, not one but two clutch pedals.

So, let me start explaining the different technologies, starting with the traditional torque converter. Now, to be fair, when I say traditional I do not mean to imply that such gearboxes are ‘old-fashioned’ anymore. Thanks to advances in modern machining and metallurgy and even hydraulic fluids, modern torque converters are extremely efficient. Simply put, a torque converter is a fluid coupling, the powershaft from the engine spins a vane that makes hydraulic fluid spin which then powers a driveshaft. This is a hydro-kinetic system, and while there is extremely complicated fluid dynamics at work here, the torque converter manages the loads on the driveshaft, either to increase or reduce the amount of torque to the driven wheels.

The first automatics were developed in the 1930s, well before the advent of microprocessors. And back then, automatics usually just had two gears — slow and fast. In fact, three and four speed automatics were the norm until a decade ago, while manual transmissions already had five or six gears.

These old automatic transmissions, while removing the work of operating the clutch, were not as economical as manuals. In fact, they were a lot thirstier. The old Maruti Zen automatic as well as the first WagonR automatic were three-speed automatics. Today, vehicles like the Maruti-Suzuki XL6 and Brezza, diesel variants of the Creta, Carens and Seltos all have torque converters. As do most BMWs, which use an eight-speed transmission developed by German firm ZF.

The internal mechanics of a torque converter are extremely complex and everything, like the rest of any modern car, is controlled by microprocessors. This is why on most modern cars, torque converter automatics are actually as efficient or even more efficient than manuals.

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The many automatics 

While in America, carmakers pushed automatics during the post-war economic boom of the 1950s thanks to cheap ‘gasoline’, in India automatics really began to take off around a decade ago when Maruti-Suzuki brought in the first Celerio with an ‘Automated Manual Transmission’ (AMT). Again, this does what it says on the acronym. Think of an AMT as a robotic replacement for your left foot that operates the clutch and a robotic left hand that switches the gear.

The AMT technology matured in the 1980s as a low-cost solution versus the complex mechanics of a torque converter. Even today, AMTs are cheap. Which is why they are offered on all Maruti hatchbacks, the Hyundai i10 Nios, the Tata Tiago and Tigor and some other cars. Having driven many of them over the years, let me assure you that they are not the most enthusiastic vehicles to drive and gear shifting feels lazy at best. But, they get the job done and when you’re stuck in a two-hour long jam at Silk Board junction in Bengaluru, performance is not what you give a damn about, resting your left calf muscles is all that matters.

In order to bring back some of the enthusiasm to such vehicles, Hyundai and Kia have the ‘Intelligent Manual Transmission’ or IMT where a driver can physically manipulate gears and while the shifts are not as crisp as a fast manual shift, it does bring back an element of manual control.

But what about Continuously Variable Transmission (CVT) on the Honda City or as Hyundai-Kia call it the ‘IVT’ on the Creta, Seltos and Verna? Well, to explain this simply, take two ice-cream cones facing each other and attach a rubber band between them. Then when those two cones slide up and down, the amount of power being transmitted if you are rotating one cone to the other cone changes. Please do not use this explanation in your engineering exam, this is not even the Cliff Notes version. But yes, this is pretty much how it works.

On some cars, there are usually some ‘steps’ between the cones (like on Honda’s) and while CVTs are not by any stretch fun to drive if you want to rocket away, they are extremely economical. During much of the second lockdown last year, I was driving the Hyundai Verna IVT and even in urban driving conditions, the car was easily delivering 15-16 kilometres per litre.

Then you get Dual-Clutch Transmission (DCT) or as the Volkswagen Group calls it, the direct shaft transmission or ‘Direktschaltgetriebe’ (DSG, it was invented by Porsche). Such gearboxes are there on the new Skoda Kushaq and Slavia as well as the Volkswagen Taigun and Virtus among others. Hyundai and Kia also offer them on the i20, Creta and Seltos. Simply put, there are two driveshafts on two clutches on cars with such transmissions, one for the odd gears and one for the even gears and reverse.

This is also why DCT cars almost always have an odd-number of forward gears. The driveshaft not being used is already primed for action. This is why DCT gear changes are faster than one can blink their eyelid. In terms of sheer driving pleasure, DCTs are at another level as anyone who has driven even the i20 with a DCT can testify, but modern torque converters are pretty good too. In fact, the extreme power output levels of cars like the Mercedes-Benz AMG and BMW M cars, mean that DCT’s have been replaced with torque converters because they can handle the power.

But none of these were the most advanced gearbox that you could buy in India, sadly that gearbox is not available anymore. It was the triple-clutch 10-speed gearbox offered for just over 18 months on the last models of the Ford Endeavour in India. This crazy gearbox was developed jointly by Ford and General Motors and when I drove it on a Ford F150 in Detroit for the first time in 2016 I was blown away. In India, it felt like too many gears though, the car was always running through the gears in traffic but whenever you did see the gear indicator saying that you’re on ‘tenth gear’ it just felt bizarre. Pity that Ford had to leave India.

@kushanmitra is an automotive journalist based in New Delhi. Views are personal.

(Edited by Prashant)

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