sjssk

A rubberband feel is a good description because that tranny is using belts. Here is the long answer on how it works:

The variable-diameter pulleys are the heart of a CVT. Each pulley is made of two 20-degree cones facing each other. A belt rides in the groove between the two cones. V-belts are preferred if the belt is made of rubber. V-belts get their name from the fact that the belts bear a V-shaped cross section, which increases the frictional grip of the belt.

When the two cones of the pulley are far apart (when the diameter increases), the belt rides lower in the groove, and the radius of the belt loop going around the pulley gets smaller. When the cones are close together (when the diameter decreases), the belt rides higher in the groove, and the radius of the belt loop going around the pulley gets larger. CVTs may use hydraulic pressure, centrifugal force or spring tension to create the force necessary to adjust the pulley halves.

Variable-diameter pulleys must always come in pairs. One of the pulleys, known as the drive pulley (or driving pulley), is connected to the crankshaft of the engine. The driving pulley is also called the input pulley because it's where the energy from the engine enters the transmission. The second pulley is called the driven pulley because the first pulley is turning it. As an output pulley, the driven pulley transfers energy to the driveshaft.

When one pulley increases its radius, the other decreases its radius to keep the belt tight. As the two pulleys change their radii relative to one another, they create an infinite number of gear ratios -- from low to high and everything in between. For example, when the pitch radius is small on the driving pulley and large on the driven pulley, then the rotational speed of the driven pulley decreases, resulting in a lower “gear.” When the pitch radius is large on the driving pulley and small on the driven pulley, then the rotational speed of the driven pulley increases, resulting in a higher “gear.” Thus, in theory, a CVT has an infinite number of "gears" that it can run through at any time, at any engine or vehicle speed.

The simplicity and stepless nature of CVTs make them an ideal transmission for a variety of machines and devices, not just cars. CVTs have been used for years in power tools and drill presses. They've also been used in a variety of vehicles, including tractors, snowmobiles and motor scooters. In all of these applications, the transmissions have relied on high-density rubber belts, which can slip and stretch, thereby reducing their efficiency.

The introduction of new materials makes CVTs even more reliable and efficient. One of the most important advances has been the design and development of metal belts to connect the pulleys. These flexible belts are composed of several (typically nine or 12) thin bands of steel that hold together high-strength, bow-tie-shaped pieces of metal.

jx3

Thanks for the edumacation!!

rockNroad

this is like the old go-kart COMET clutch.
good post !!

rNr // mike

tonepad

Nice to know a bit more about CVT tech...thanks. Whether it can catch on with the American public remains to be seen. Anyone remember the first year of the Mini. CVT was offered and quickly removed from the options list after it was found to be unpopular...seems we like that "shifting" feel. I do think it's smart technology and much simpler than the average auto trans. Unfortunatley I think the Caliber may not help the CVT reputation. I will say that I am seeing quite a few on the Socal roads though. Of course it is also available on quite a few more upscale vehicles like some Audi models and the Nissan Murano. Controlling RPM is good step in the quest for better fuel economy.

Grohlinator

When our MINI was in the shop the dealer gave us a rental MINI with a CVT in it. I hated it. It felt like a slipping tranny. Give me the supercharged 6 speed manual Cooper S any day!!

tonepad

Yeah BayBay, rowin' a 6 speed Getrag...that's what I'm talkin about! I absolutely adore Minis and want one in the worst way but unless I can justify a third car it ain't happenin for me anytime soon. Motor on brother!!!

Snoopy

Isn't the Mini cooper S, turbocharged with like 173 HP?? At least my nephews is.....plus some other special Mini Cooper over the counter stuff, he puts out the 207hp version.

tonepad

The stock factory Cooper S is supercharged. There is a works edition but I don't know if it's Turbo'ed or just a more juiced up blower package. Dang I still want one someday.

Grohlinator

The second generation MINI that came out this year is turbocharged, but up untill now they were supercharged. Our's is an '05 and makes 168hp. Your nephew must have the supercharged one because there are not any parts that put the turbo over 200hp( at least not yet!!) I personally love how the supercharger sounds compared to the new turbo. Check this video out, and you'll see what I mean


http://www.youtube.com/watch?v=tBZzE9jf9C8

Grohlinator

Do what ever it takes to get one! It's soooo worth it! They are so much fun to drive. The six speed is amazing, the clutch is very direct, and the handling is fool proof. Not to mention the engine is a beast. With the TC off she'll lay rubber in the first two gears no sweat.