CFour said:
LMN8R Its hard to explan how the CVT works. There is no shifting. The transmission has like a "sliding" gear ratio (a chain I think) and by computer slides into exactly the right ratio for the task on hand. You feel no shifting at all only added transmission drag (low gear) when slowing.
To expand on CFour's post a little more. The belt or chain connects to two pairs of conical pulleys. The points of the cones are facing eachother and the chain sits in the valley. The gear ratios change by the pulleys being moved closer or further appart allowing the chain to "slip" up or down gripping a larger or smaller circle, thus changing gear ratios. I believe that's a good basic description on how they work.
I think you can compare it somewhat to how a bicycle's gears work. How the bike chains "slide" up and down the multiple cocentric gears to change gear ratios. Except you have an opposing set of "gears", a smooth cone rather than descrete gears/spokes, and the chain straddles both cones. That may help you visualize it, or it may confuse you even more.
From a stop you feel the low gear just sort of "melt" away to the higher drive positions. Its really neat and Im surprised the big 3 isn't there yet. Im guessing someone holds a patent (Honda I think) and the big 3 refuses to pay for the rights.
I don't think it's a patent issue only as I believe the Saturn SUV (VUE?) is available with a CVT. I know it used to be a power issue. CVTs originally used rubber belts and they couldn't handle high power engines (around 200hp or ft-lbs of torque would cause the belts to break).
Audi developed a special chain to handle high power engines. It's somewhat complex. You have "2-Dimensional" chain links connected to form a loop, and there are several of these loops connected to give the chain significant width.
Nissan has a different solution for highpower CVTs. IIRC, they use two pairs of gears, we'll call them A1, A2, and X1, X2. A1, A2 face eachother and are conical in shape with "points" on the inside. X1, X2, are more like normal gears but I believe the teeth are rounded slightly. The Xs connect the As and are on opposite sides of the A's axis. The A gears can vary their distance from eachother, the X gears do the same and can change angles. The varying in angles changes effective gear ratios. I believe Nissan is putting this in their Skyline (Infinity G35) GT-8 model. 8 for 8-speed.
I have read that there are prototypical CVTs that can handle larger amounts of torque, but I haven't seen any in cars. Though Nissan's "gear-based" CVT should be able to handle 280+ ft-lbs as the 3.5L it's mated to puts out about that much HP. When using gears rather than belts/chains, that'd give it much better power handling.
As far as tiptronic goes the CVT is ideal for this because it haS the ability to slide the trans in just the right spot to make the Shift "feel" real.
I wished Audi would have the CVT in their Quattro models. That'd be nice: CVT and Quattro.
I think that Audi seems to set the standard in interior quality. I think Lexus and BMW come in not far behind. But, for a sports car, I care about nice supportive seats and not much else. If a Z06 had no radio, I don't care! I'd have a 8cylinder sound system!
