The standard automatic gearbox, sometimes referred to as a torque converter’ has four, five, six or even 8 with the BMW. The gearstick is pushed backwards or forwards and has the controls: P for Park which you use when the car is at a stop, R for Reverse gear, N for Neutral, D for Drive which is the standard choice for general driving where the gears are changed automatically as the revs increase or decrease, and the rarely used option to choose the gear range yourself which are labelled 1 or L for low, 2 and sometimes 3 depending on how many gears the automatic gearbox has, these are used for winter driving, towing and descending hills to take the strain off the brakes. There may also be a S for Sport where the gears will change when the revs reach a higher point so the car will accelerate faster. The advantages of this method of driving are obvious, you have a stop and go pedal in the brake and accelerator meaning you can control the car with one foot, usually the right foot, the downside is that the gear changes can be a tad sluggish and there is generally a loss of power and the fuel consumption of the car takes a big hit over the manual equivalent. Over the years the Automatic gearbox has evolved to deal with these issues, we how have a DCT a CVT and a clutchless semi automatic, so what does all this mean and which one should you choose.
The Semi Automatic
With a semi automatic you have a very simple control and you choose if you want to change gear yourself or want the car to do it for you, once in motion you simply push the lever forward to change up a gear or push it back to change down a gear or leave it alone and the car will change gear itself, in some cars you have the option to control the gearchange from buttons or paddles attached to the steering wheel. The semi automatic is a manual car with an automated clutch so you see very little loss of power or effect on the fuel economy, they are however a little basic compared to the new Dual Clutch Transmission units available. Example of Semi Automatic units are found in the Fiat Group as a Dualogic, Citroen and larger Peugeot as ESG or 2Tronic for the small Peugeot and Toyota cars.
DCT (Dual Clutch Transmission)
The DCT is a very clever system which is an advancement of the Semi Automatic gearbox where two automated clutches are used, one for the odd gears and one for the even thus increasing the speed of gear selection and giving the driver the real option of an automatic car with the option to have manual gear selection, gearboxes have either six or seven gears. With a DCT gearbox fitted you have almost no loss in power or fuel consumption and is the modern choice, the downside is that it is an expensive option for manufactures to implement into production, thus the two big advocates are Ford with its Powershit unit and the VW Group with its DSG box that goes into its the Audi, Seat, Skoda and Volkswagen cars.
CVT (Continuous Variable Transmission)
Initially drafted by leonardo Da Vinci in 1490 a CVT is a type of automatic transmission that uses a moving pulley system and a belt or chain to infinitely adjust the gear ratio across a wide range. CVTs also reduce shift shock and increase fuel efficiency significantly. But CVTs can’t handle the high torque demands of performance cars and are generally fitted to cars with small petrol engines, electric cars and cars with two powersources, ie Hybrids.
Automatic cars were designed for comfort and ease of driving but traditionally they are very heavy and take power from the car and therefore hit the fuel consumption greatly, the more modern gearboxes have five or six gears and are smaller and lighter and loss to power and fuel consumption is not as drastic, but the DVT boxes are quite a revelation and knock spots off a semi automatic gearbox, as for CVT’s they are only good for hybrids and electric cars really. We always recommend you arrange a test drive prior to choosing any car and if you are getting an automatic for the first time then it is essential. Hope this helps our recommendations for the best automatic cars can be found here. Best Automatic Car offers