Continuously variable transmissions... how do they work

[SadbutTrue]

Obviously this has little or no bearing on our mustangs, but I have seen these more and more on econo-bangers (mostly hybrids, but i saw one on a normal n/a 4 banger too) in magazines and such. Basically under transmission type on the little car info table (that usually says x-speed auto or x-speed manual) says continuously variable automatic.

How do these work? Do they have a huge impact on acceleration/fuel mileage? Any info would be nice.

 

[88 Fox GT]

Ok, they are actually as simple if not more simple than a manual transmission. Their advantages are that they can keep the engine in it's powerband the whole time. For instance, if your car makes max power at 3500 RPM, the tranny will keep the engine at the RPM the whole time your accelerating, creating drastic acceleration increases because your car now has a "flat" power curve. At max power all the time when WOT.

There are all kinds of CVTs, some are hydrostatic (pretty complexed) others are a "belt" or "metal-belt" between two pulleys. One of the pulleys has an adjustable width because it has a spring on one side that can be pushed out. As the speed of the vehicle increases, the "belt" slides down in between the pulley even further as the pulley pushes out further, increasing the gear ratio. Understand?

They can give you better fuel mileage and all around better performance. They are what cars will have in the future for the best performance.
Only bad thing is, the constant "WHAAAAAAAAA...." of the engine won't change (no shifts at all).

But I have ridden a pretty power twin cylinder ATV with a CVT on it and it pulled very hard the whole time on the throttle because it was constantly in it's powerband, all the time, no doubt at all. No more "I wish I had a gear between this and this". It's a continuously variable amount of "gear" ratios.

This page has a pretty good explination of how the CVTs work.
http://www.edmunds.com/ownership/techcenter/articles/45104/article.html

 

[Route666]

I'm almost positive there is good info on this on www.howstuffworks.com

I remember looking at it once.

I couldn't find it just now, but do a search on google.

 

[XStang302x]

Yamaha puts those in their scooters.

-Frank

 

[351carlo]

These really are amazing little transmissions. I'm on a National Engineering team, and about 2 years ago we decided to recreate our own CVT. Basically in the beginning, the original drivetrain ratio was 7:1, thus making the best torque down low to get the vehicle moving. Once the torque load was the least (Aka when you're cruising in overdrive, or for those of us with stinky 3 speeds, when you're trying to idle in 3rd), the final ratio was 1:7. Just think about the possibilities.

My Mustang's top speed would have been INSANE, if I could find a reliable method to build a transmission like this. I believe some of the Mini Cooper's have these in them.

 

[fvike]

The best CVT in the world is probably the Audi Multitronic. It has an metal chain that's made of over 1000 links. This makes it able to take more torque than metal-spun bands, and there is no risk of the chain slipping. Have a look at it here. http://www.audi.com/com/en/new_cars/driveline_suspension/multitronic/multitronic.jsp

Audi test shows that the multitronic is faster than an manual transmission, and smoother than an automatic.

The Variator and the tourque-sensing unit is the key components of the Multitronic. You can read more about that on that link.