New to the forum and have seen this CVT often. Did a search and can't find a definition. What's it mean?

 

Constant Velocity Transmission (spelling may be off)

 

http://en.wikipedia.org/wiki/Continu...e_transmission


Infinite gears. No shifting noise.

(and really freaking expensive to replace from what I hear )

 

Actually, it's Contiuously Variable Transmission.

No fixed gears. Imagine the bellcrank and rear gearset of a multi-speed bicycle. Now imagine the gears as cones. As the chain is guided along to the smaller-diameter tip of the cone, the effective gearing is higher numerically (taller). No steps from 0 mph to top speed. The CVT can also park the engine at a ceratin rpm (throttle position-dependant) and the vehicle will accelerate steadily.

Constant Velocity Transmission is, well, a contradiction in terms. If a vehicle needed a constant velocity, it would not need any transmission.

 

Now that is cool. That is how model helicopters work..

 

Some companies have put fake shift points into the CVT's because it is very unusual to drive one of these-it just never shifts. They are efficient and often aide fuel economy but the "feel" of it is odd. My Mom's Prius has one.

 

if you want an idea how it looks, go open the hood of a snowmobile. granted its not as complicated or intricate as whats drives a car, but it will give ya an idea.

 

This idea has been around a long time in various forms.
In the 50's a car was made in Holland I think called the DAF which had a variable transmission using standard V belts.
My father had a big wheel garden tractor called a David Bradley which had a variable transmission using a V belt .
The concept is simple.
If the drive pulley on an engine is 2 inches in diamater and the driven pulley is 2 inches in diamater both shafts turn at the same speed. If the driven pulley is changed to 4 inches in diamater then that shaft turns SLOWER. The variable transmission is created when the two shafts are fixed but the pulleys are variable in size, as one gets larger the other gets smaller and the speed of the shafts change. If you ever SEE this in action it becomes clear but trying to write it down is hard.

 

Most commonly used in scooters. Shift points are more then just to ease people driving the car, they assist in traction control. Try a scooter on snow or ice, the trans instantly goes to highest gear. Actually it's alot of fun.

 

I agree. It's very hard to explain. Our Baja SAE guys use a cvt on a Briggs 10hp engine to power their vehicle. In theory, cvt's are more efficient than any other transmission. They are able to keep the engine at the most efficient rpm and hold it there (or at the highest power output if that's what's wanted). The problem is that a cvt is always slipping a little just like the torque converter on an autobox. Also, there is a lag associated with them since the belt or chain has to slip up or down the cones when you hit the throttle.