by Pat Goss
The eternal problem with automobiles is how to harness the energy produced by the engine and transmit that energy to the drive wheels of the vehicle to make it move. Well, that of course has always been done by the transmission, and transmissions have always had gears in them so that you can go from one gear ratio to another to accomplish power to begin with and then speed as it moves down the road.
Well, the most popular version of that these days is going to be the automatic transmission. Automatic transmissions have gears in them just like a manual transmission. The big difference is that it uses hydraulic pressure and electronic controls to shift through the gears. They work very, very well. That’s the reason they’re so popular.
But there’s a new type of transmission on the market. It’s been out a few years now and it’s really gaining in popularity lately, and that’s what’s called the CVT transmission, constantly variable transmission. Now essentially it doesn’t have gears in it. Well, how could that work? Well, it uses two pulleys with a metal belt between the two pulleys. Now both pulleys are adjustable and they’re controlled by the computer and hydraulic pressure. Now the way it works is very simple. The computer commands one of these pulleys to spread out. As that pulley gets wider, the belt goes down into it deeper. Well, at the same time the other pulley is squeezed together so that the belt rides higher. This changes the ratio between the two pulleys and it does away with the shifting of gears. It is indeed constantly variable, so you don’t get the sensation of shifting like you do with a conventional automatic transmission.
Now they finally made these so they can withstand quite a bit of horsepower, and they change the driving experience dramatically. So before you buy a car with a CVT transmission in it, spend some time behind the wheel and make sure that you don’t find the driving experience too different for your tastes.
If you have a question or comment, write to me. The address is MotorWeek, Owings Mills, MD, 21117.