Technically the CVT is brilliant. They just require a different driving style. Once you get use to the car acclerating without the revs picking up they arnt to bad. In fact on the freeway theyre great.

I must admit on twisties they are dreaful.

Good fuel economy. Lots of cars have them now - Audis FWD gerabox is a cvt as is the new Nissan Maxima

how is cvt different to having, say, an electric motor...

constant torque?

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well in one way your right, but you've missed the blindingly obvious that they are very different. and electric motor can't be compared to a internal combustion engine. The frictional losses in them are totally different and therefore they need to be delivered differently.

CVT is a good idea that has been poorly executed in some examples of motoring and a lot of mechanics don't know how to do anything with them. It's still a specalist thing.

the electric motor can't actually be like a engine with a CVT gearbox unless it has a CVT gearbox as well?

The idea of CVT is to only push the motor as hard as it needs to be pushed to do it's job, and electric motor will only spin as fast as the wheel is going

the biggest downside of a CVT is their is no engine brakes, similar to an auto but much more noticable, because it will idle as you lift off the accelerator whereas an auto will stay in gear.

I have driven a CVT and it requires a different approach to driving than a manual or auto box. Great idea that can deliver maximum power when needed. But like everything different it's expensive to develop properly and maintain. And if people don't want to adapt to the change while driving one then it's a shame but manufacturers take them off the market if they cost them too much

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-doing a Degree in Mechanical Engineering,
and a few conversions:
13B Extend in a 1600
4EFTE in a mini ute (all slowly)

i'm aware that they're different, but i'm curious about the loss of torque when you lift off.... does that happen in an electric motor?

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if properly set up both of them will only loose as much power as how far you lift off the accelerator. the accelerators not a switch it's a control.

in lifting off

the electric motor generally will want to slow as really you are controlling an amplifier in an EV this controlls engine speed more than power supplied. But this isn't true in all cases sometimes a computer controls the accelerator to keep speeds constant (more in line with a standard cars controls)

a CVT will just turn down the power supplied to the wheels, as the engine drops revs. This has the dynamic of *at low speeds* having no noticable change* but as wind resistance increases with speed the car will slow due to this *at high speeds* the car would slow down more by air resistance than the motor

theirs no reason that you couldn't get a CVT to increase the revs as you lift off to increase the "engine braking" though but most people wouldn't know what to do with that.

does that help a little?

_________________
-doing a Degree in Mechanical Engineering,
and a few conversions:
13B Extend in a 1600
4EFTE in a mini ute (all slowly)

yeah it does.. ta..


that and i just googled some more on the subject instead of high-jacking this thread..

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both technologies CVT and EV would be determined on their driveability by microprocessor controls and the characteristics on how they work in what conditions. This would also be adaptable in some cases to how a car is driven.

Adaptability is not always a good thing as it detracts from the expected result in all situations and this can create a headache in trying to second-guess a computers 'mood'

in any way a CVT isn't for everyone, I like my manual, gear ratio's are easy and I know what speed I am doing in 5th without looking by the engine note. But I think I would give one a shot over a standard auto. Because I hate Auto's lazy inefficient and limited control of a car in trying conditions.

good for towing, straight line and big cars though, just not my thing

OK class dismissed

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-doing a Degree in Mechanical Engineering,
and a few conversions:
13B Extend in a 1600
4EFTE in a mini ute (all slowly)

I believe not much people have been enjoying CVT here in Australia.
It is quite strong in Japan, and has been a bit in Europe. In Europe they missed the 80ties. that was the time they would have been great to sell them.
These days automised transmissions are cheaper and offer the same efficiency.
The problem for the CVT is that car manufacturers see it as an automatic.
Well it is not.
It is kind of manual with 1000 gears, that can be chosen anytime the driver wants it.
Only because most of the CVT systems are not so good with shocks in torque that an automised clutch is used. So the driver is not able to rev up to 7000 RPM and let the clutch come up, such as done in burn outs and so. I have build cvt with normal cluch for prototypes, and driven it as manual transmission.
CVT as used these days act as automatic, because people expect it to be so. They offer better fuel economy as normal automatics and can offer better performance as manuals. It just depends how the car manufacturer wants to tune the car and give the car the image.
For a lot of people automatic cars are related to elderly persons.

The fact that CVT has no or not much engine brake is for fuel economy. It is jut removing a little piece in the hydraulic control unit to take it away and act like a manual car. These days, is is even easier with electronics.
Just programming the shiftpattern you want.

Most of the prototype cars these days are using CVT. Especially hybrid and electric. Because the CVT can keep the electromotor in a constant speed, where it has his most efficient area. Another point for CVT is the constant power on the wheels when changing ratio. Electromotors are very bad changing their speed in tenths of seconds.

Regards, Jo

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fun to drive