Why don't more cars use CVT?
Discussion
On the subject on Continuously Variable Transmissions...
Why don't more cars make use of these? Is it a consumer taste thing? Manufacturing cost?
The case for them, as I can see. I'm no great fan of old fashioned torque converter automatics although I've seen some reasonable ones, in the right car. My old A8 and Jaguar XJ were good because their V8 engines could simply throw petrol at the gaps in gear ratios to generate power and accelerate (and the A8 really could shift).
I've recently bought a CVT equipped hybrid and the technology seems to make great sense there. I was advised that the transmission would be a love-or-hate affair simply because it's so polarising in the way it operates. My experience of it is that it's a clever system which works well and seems to contribute to fuel savings, which is obviously a selling point for many cars these days. Even the most potent of cars now brag about their headline economy figures.
The downsides of the CVT are mainly the noise and sensation under acceleration. That is the first issue to address and what I reckon will account for the majority of drivers who don't like the CVT. The noise under heavy acceleration is a flat buzz. The acceleration doesn't feel that fast either because you don't have that noise to compare with the increased speed, you just get one tone that instantly stops when you reach your desired speed.
In their favour, they seem to suit smaller cars and hybrids because they can always find the best ratio for acceleration and cruising. My hybrid will cruise at 70mph at just over 1000rpm on occasion. My XJ would be around 2000rpm at the same speed. Because of the elastic response of the CVT, it's always willing to and able to instantly select the right ratio to provide instant acceleration when you open the throttle. There is no shuffling of gears or manipulating the throttle before a corner to precipitate a shift to the right gear, it seems to simply provide the best propulsion available at the drop of a hat before settling back to low rpm when you ease off the throttle.
Aside from under heavy acceleration, there is very little perceptible noise made. It's apparently both lighter and more mechanically simple than a torque converter box. It doesn't suffer from having to compromise a set selection of gears (and I've no doubt my car would be a dreadful drive with a traditional auto transmission much like every other small auto I've driven). Given the fact if has a lot going for it, why isn't the CVT more popular? It has gained a tiny bit more traction in America and Japan than it has in Europe, it appears.
It's never going to challenge a dual clutch box* or even an 8 speed auto for driving pleasure (it'd rob a sports car of it's revving noise!), bite as a solution for every day cars it seems ideal. There have been CVT equipped cars on the market for donkeys years, and manufacturers have the final say on what they fit. I wonder why it hasn't proliferated further?
Why don't more cars make use of these? Is it a consumer taste thing? Manufacturing cost?
The case for them, as I can see. I'm no great fan of old fashioned torque converter automatics although I've seen some reasonable ones, in the right car. My old A8 and Jaguar XJ were good because their V8 engines could simply throw petrol at the gaps in gear ratios to generate power and accelerate (and the A8 really could shift).
I've recently bought a CVT equipped hybrid and the technology seems to make great sense there. I was advised that the transmission would be a love-or-hate affair simply because it's so polarising in the way it operates. My experience of it is that it's a clever system which works well and seems to contribute to fuel savings, which is obviously a selling point for many cars these days. Even the most potent of cars now brag about their headline economy figures.
The downsides of the CVT are mainly the noise and sensation under acceleration. That is the first issue to address and what I reckon will account for the majority of drivers who don't like the CVT. The noise under heavy acceleration is a flat buzz. The acceleration doesn't feel that fast either because you don't have that noise to compare with the increased speed, you just get one tone that instantly stops when you reach your desired speed.
In their favour, they seem to suit smaller cars and hybrids because they can always find the best ratio for acceleration and cruising. My hybrid will cruise at 70mph at just over 1000rpm on occasion. My XJ would be around 2000rpm at the same speed. Because of the elastic response of the CVT, it's always willing to and able to instantly select the right ratio to provide instant acceleration when you open the throttle. There is no shuffling of gears or manipulating the throttle before a corner to precipitate a shift to the right gear, it seems to simply provide the best propulsion available at the drop of a hat before settling back to low rpm when you ease off the throttle.
Aside from under heavy acceleration, there is very little perceptible noise made. It's apparently both lighter and more mechanically simple than a torque converter box. It doesn't suffer from having to compromise a set selection of gears (and I've no doubt my car would be a dreadful drive with a traditional auto transmission much like every other small auto I've driven). Given the fact if has a lot going for it, why isn't the CVT more popular? It has gained a tiny bit more traction in America and Japan than it has in Europe, it appears.
It's never going to challenge a dual clutch box* or even an 8 speed auto for driving pleasure (it'd rob a sports car of it's revving noise!), bite as a solution for every day cars it seems ideal. There have been CVT equipped cars on the market for donkeys years, and manufacturers have the final say on what they fit. I wonder why it hasn't proliferated further?
- I should add that, were I designing the perfect sports car it'd be a manual with a TVR badge, though Porsche's PDK is fantastic.
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