CVT: a good idea, or the worst transmission ever?

[Kyng]

Most cars will have a gearbox with between 5 and 10 gears: the higher gears allow for higher speeds, while the lower gears provide more power for starting and acceleration. But some cars instead have a "continuously variable transmission" (or CVT) where, instead of changing between a series of fixed gear ratios, the ration changes smoothly as you accelerate. In theory, this is great - and, it worked so well in Formula One that it got banned . So, what are the problems? The above video explains:

• How CVTs work: They don't have gears . Instead, they have two pulleys, connected by a belt. The pulleys can vary in size (as shown by an animation in the video), thus changing the effective gear ratio.
  
  
• Why they should be good: With a normal gearbox, each gear ratio has a specific speed at which maximum power is delivered. However, with a CVT, you effectively have an infinite number of gear ratios - so no matter what speed you're going at, the CVT can always find a ratio that will achieve maximum power. Added to this, they're simple; well-understood because they've been around for so long (the first one was invented in 1896); cheap; and allow for better fuel economy.
  
  
• Why people don't like them: If you've ever been in a car, you'll know what acceleration usually sounds like . The engine noise gets gradually higher in pitch until you change gear; then gets higher in pitch again until you change gear again; a bit like this . But CVTs don't sound like that - so it feels like they take longer to accelerate (and this is partly true: the CVT takes time to select the correct ratio!). Customers are so bothered by this that modern CVTs are actually designed to simulate traditional gear shifting . However, that kind of defeats the point of using a CVT to begin with!
  
  
• Reliability: CVTs may be old and simple, but that doesn't make them reliable. The belt and pulley system creates a lot of friction, which in turn creates a lot of heat, and a lot of wear on the belt. Indeed, some CVTs require additional external coolers - which eliminates many of the cost savings!
  
  
• Power limitations: Because of all the heat (and all the wear), there's a limit to how much power can be realistically achieved with a CVT. They're fine on scooters - but not on racing cars, which will wear out their belts too quickly .

I've never driven a car with a CVT - but, one of my friends used to have a Nissan Micra with one. This didn't have the fake gear-shifting nonsense (it was a 1996 model, from before that became a thing) - but, it also didn't have the sound that we often associate with acceleration: the engine noise was just a continuous, unchanging hum . Still, it seemed fine at getting us from place to place!

So, have you ever driven a car with a CVT - and, if so, what do you think of them?