Ford Fiesta AT unveiled: Understanding its six-speed twin-clutch gearbox

Ford has unveiled the soon to be launched Fiesta automatic in India. The good news is that this is a “Powershift” six-speed dual-clutch automatic transmission (only in the petrol variant), and not the five-speed Durashift we thought Ford might bring into the country. So what’s the difference between this gear-box and how does it affect the cars performance? Read on to find out how this gearbox and automatic transmissions function in general.

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Photo: The all New Ford Fiesta AT will be a very efficient automatic

The six-speed dual-clutch automatic is a very efficient automatic transmission, which has faster shift timings than even a manual gearbox and lesser power losses. It actually makes the automatic Fiesta a little faster in pick-up without compromising on fuel efficiency compared to its manual counterpart.

The bad news is that the automatic transmission will be offered only on the 1.5-litre petrol variant of the Fiesta. CarToq will bring you a full review of the Ford Fiesta automatic soon. The Fiesta AT will also sport a hill start which prevents the car from rolling backwards while going up inclines. The car stays in its place for 2.5 seconds after the brake is released so that the driver can accelerate and continue moving upwards.

The introduction of the Ford Fiesta dual-clutch automatic brings buyers more choice among cars with automatic transmissions. The Ford Fiesta is the only car among its rivals to sport a dual-clutch automatic.

The other choices at the same price point (around Rs. 10 lakh) include the Volkswagen Vento petrol automatic, with a six-speed torque convertor automatic transmission, the Honda City with a similar 5-speed automatic transmission, with a paddle shift option, the Hyundai Verna petrol and diesel with a 4-speed torque convertor automatic with tiptronic (manual shift) mode and the SX4 petrol with a 4-speed automatic. The last generation Honda City had a CVT automatic gearbox. See our Ford Fiesta gadget gallery here.

So what makes the dual-clutch automatic superior to the other two varieties seen in the Indian market, namely the torque-convertor and the CVT or continuously variable transmission? Let’s make it easier for you.

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Photo: The Fiesta's automatic gearbox improves both mileage and performance

Dual-clutch automatic transmission

Other popular cars in India that offer a dual-clutch automatic transmission are the Skoda Laura automatic direct-shift gearbox (DSG) and the Volkswagen Jetta automatic. These are priced much higher than what the Ford Fiesta automatic is likely to be priced at.

A dual-clutch automatic transmission is mated to the engine using a combination of two electronic clutches (one within the other) that engage with the engine flywheel in turns. One of the clutches runs the odd gears in the gearbox (gears 1, 3 and 5), while the other turns the shaft which has the even gears (2, 4 and 6). What this allows for, is much faster shifts between gears, because even before one clutch disengages, the other one engages for the next gear, making shifts even faster than a manual transmission, resulting in minimum power loss. Also read: Ford Fiesta Manual first drive impressions

What this does, is make the car pick up much faster and does not compromise on mileage. On the downside, it’s much more expensive than a traditional automatic (torque convertor) gearbox.

Traditional automatics (torque convertors)

Traditional automatic gearboxes such as the ones found in the Honda City, Hyundai Verna and Maruti SX4. The gear ratios are fixed in the automatic transmission gearbox (and can also be manually selected in some), but these gearboxes have a device called a torque convertor that replaces the normal clutch you find in a manual transmission.

The torque convertor relies on a viscous fluid to provide power to the gearbox from the engine. The engine is constantly churning the fluid in the torque convertor and will only manage to turn the transmission if a certain RPM or torque load is reached (when you rev the engine or take your foot off the brake). There is a loss in power because the torque convertor device works like a constantly slipping clutch in a manual transmission.

Because of this, while shifts are smooth, there is a loss in pickup and subsequently a loss in mileage with traditional automatics. But they are most convenient to drive in congested city traffic, and are not as expensive as the dual-clutch automatic system.

Continuously variable transmission (CVT)

Remember the good old Kinetic Honda scooter? That’s the easiest example of a continuously variable transmission to understand. Among cars the last generation Honda City and the present Renault Fluence petrol and Maruti Kizashi offer CVT transmissions.

A CVT gearbox has an infinite number of gear ratios, because the transmission is essentially made up of belts slipping over cones, where the larger end of a cone giving you lower ratios (akin to first gear, second gear etc) while the tapering end gives you higher ratios. As engine speeds increase the belt slips from the larger end to the smaller end of the cone, altering the gear ratios constantly. Some cars like the Kizashi and the Fluence offer you preset speeds that can be manually selected as well.

CVTs have a rubber band effect, where the engine RPM rises very fast before the car actually begins to pick up speed (again, remember the way Kinetic Honda’s used to sound?) This results in larger wastage of fuel and losses of power. However, these are the cheapest kind of automatic transmissions that can be manufactured and are easy to maintain.

Conclusion

Of the three kinds of automatic gearboxes that are available on cars in India, the dual-clutch automatic is the best in terms of fuel efficiency and minimizing power losses. It’s a good decision on Ford’s part to bring this transmission option to the Fiesta, as it will make the car even more drivable without compromising on its sportiness. But it remains to be seen by how much this transmission is going to increase the price of the already expensive Ford Fiesta.