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New automatic transmissions for small cars

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D icke friends they haven't become so far, small cars and automatic transmissions. Although every third new car buyer in this country does without manual work when changing gears, the automatic rate under the short ones is just 5%.

In addition to the high surcharge for automatic transmissions, which is particularly painful in cheap cars, there are also technical reasons in the way of success: Small, low-performance engines do with a classic automatic torque converter that uses the engine power is transmitted via two paddle wheels running in an oil bath, particularly difficult. Tough starting and significantly poorer performance are the result. In addition, the four-speed machines, which are still often found in the lower segment, with their large gear ratio jumps, noticeably increase fuel consumption. Additional consumption of around one liter /100 km according to the ECE standard is therefore not uncommon. In addition, they can only be combined with start-stop systems with great effort.

Small cars with automatic systems have a future

However, transmission experts predict a bright future for automatic systems in small cars too. The proportion should triple within the next five years. However, continuously variable transmission (CVT) and double clutch types should make the race. The latter consists of two half gears in one housing, between which a clutch is used to switch back and forth. Since this happens in a split second, gear changes take place with almost no interruption in traction. Because there is no power in the torque converter and the transmission types have six or seven gears, some double clutches are more economical than their colleagues with manual gearshifts. In addition, they can be easily combined with start-stop systems, as they can be operated when the engine is not running without the need for a minimum oil pressure.

After the double clutch pioneer VW has now introduced the DSG in Polo & Co. offers, other manufacturers are following suit: Alfa Romeo is supplying a newly developed six-speed dual clutch transmission for the Mito, which can handle up to 350 Nm despite the use of an efficient dry clutch. In addition, the 2011 Ford Fiesta will start in the USA with a six-speed direct shift box called Powershift, which will also retire the antiquated four-speed automatic transmission in Europe. As the number of items increases, the costs should fall, so farMain disadvantage of DSG technology.

Automatic converter is reserved for large models

Automatic converter has also made great strides in recent years. Current types with seven to eight stages and sophisticated converter bridging only lead to low consumption surcharges. Even start-stop systems have been integrated. Corresponding noble gears are very large, which leads to space problems in small cars with transversely installed engines. Because they are also really expensive, they will remain the privilege of the upper middle class and upper class.

The future of automated manual transmissions, which some manufacturers have in their product range, is also viewed with skepticism. Here servomotors take over the clutch and gear changes. Such systems can be manufactured inexpensively because they are based on existing, conventional transmissions and do not have any disadvantages in terms of consumption. However, long interruptions in gear changes noticeably reduce comfort, as smart drivers confirm with a nod.

CVT transmission with unmatched spread

The situation is different with the CVT transmission. In Asia it has long been a hit with the little ones, but it could also come out of our niche existence. Since the engine power is transmitted via a link belt that runs between two sliding bevel pulley wheels, the ratio can be continuously adjusted. The result is jerk-free and therefore comfortable acceleration. Nissan wants to solve the main problem of the limited gear ratio spread with a newly developed CVT with integrated overdrive, which comes in 2011 in the new Micra. The resulting spread of 7.3: 1 even exceeds that of many conventional transmissions. This means that you can drive economically and at low speeds even at higher speeds. In addition, it should be combined with a start-stop system. So the signs are perfect that the cool relationship between small cars and automatics will turn into hot love after all.


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