Should I Buy a CVT or Conventional Automatic Transmission?
QUESTION
From: Esrael
I have been reading your answers to many questions about cars. I just want to ask what are thoughts about CVT vs Sports Automatic.
ANSWER
CVT stands for 'Continuously Variable Transmission'. These use a belt and expanding/contracting variable pulley system to change the drive ratios.
CVT uses expanding/contracting cone-type pulleys to vary the drive ratio infinitely between the lowest and highest possible ratios
Typical CVT installation - another benefit of which is compactness and comparative simplicity
Basic CVT operation: When one pulley expands, the other contracts, and vice-versa. Revs can therefore be maintained at a constant as road speed changes
This is a CVT from something like a ride-on lawnmower. That's right - CVTs were invented not because of miraculous fuel-saving ability, but because they're cheap
The short answer is: CVT is better for fuel efficiency, but not as nice to drive - especially if you like to drive in a spirited, engaging way from time to time (like on a favourite piece of twisty road).
CVT is better for fuel consumption because frictional losses are minimised and also because the engine is held at its most efficient operating revs for as long as possible. There are no gear changes as such - the expansion and contraction of the drive pulleys varies the drive ratio continuously and infinitely (at least, infinitely - meaning 'without steps' - between the end points of its operation). These are the good points - and they are good.
CVT installations in cars typically need strong steel belts to facilitate the required torque transfer
Unfortunately, CVT sounds and feels like a conventional manual with a slipping clutch when you drive like you mean it. The CVT keeps the engine at the revs designed to deliver peak power, and the sense of positive engagement that comes from the road wheels being 'joined' to the engine in a fixed way is lost. It just doesn't feel or sound as good. (At lower revs, when you're just commuting, CVT isn't so bad. The transmission holds the engine at the kind of low revs it needs to be at to operate efficiently.)
Some CVTs have incorporated paddle shifters and sports modes that allow the driver to select distinct ratios for performance-style driving - which is a kind of neat compromise.
Steel belt from automotive CVT drive system
Steel drive belt in situ
In a sense it's down to personal preference - like iPhone versus Galaxy, or Mac versus PC, or Megan Fox versus Kate Upton. They will all do the job; what really matters is how you'd prefer the job done. (Make mine the conventional auto, the Galaxy, the iMac and Kate...)
PS - I'm not so sure what the term 'sports' means in relation to automatic. Presumably it means the ones you can drive like a manual when you want to. Personally I think the paddle shifters are a bit of a joke - especially the paddles that don't move with the steering wheel. I prefer the shifter you move left or right to engage 'tiptronic' mode - and I find the cars where downshifting is a forward nudge on the lever a better option than those that downshift rearwards (like braking, downshifting has to do with slowing down generally). And I hate those stupid 1980s-style notched transmission selector patterns (think: current Mazda6). These are always optimised for left-hand drive.
See also: How to beat a car dealer