CVT New Technology?
1 - 14 of 14 Posts
Joined
·
2,243 Posts
Correct. The technology has been around for quite some time (30 years seems right) but the Murano is (I believe) the largest vehicle to incorporate a CVT. Generally speaking the CVT has been used in very small applications (go-karts, golf carts, that type of thing).
I did a little research on it when I was first introduced to the Murano, and found a lot of good information on the web. Don't seem to have many of those links still floating around, but here's one with some good technical info:
http://cvt.com.sapo.pt/toc_en.htm
Subaru came out with a vehicle incorporating the CVT quite a few years ago, but it was a huge flop. Then Audi re-introduced it in some of their A4 models (I think in 2002). Now the Murano has it, and the Cooper S as well (for 2004).
So to really answer your question:
Old concept/technology with a new application (and some new technology).
~ Corin
I did a little research on it when I was first introduced to the Murano, and found a lot of good information on the web. Don't seem to have many of those links still floating around, but here's one with some good technical info:
http://cvt.com.sapo.pt/toc_en.htm
Subaru came out with a vehicle incorporating the CVT quite a few years ago, but it was a huge flop. Then Audi re-introduced it in some of their A4 models (I think in 2002). Now the Murano has it, and the Cooper S as well (for 2004).
So to really answer your question:
Old concept/technology with a new application (and some new technology).
~ Corin
Joined
·
8,402 Posts
It is important to distinguish between new technology and new applications of that technology.
CVT technology has been around for a while, but it has not yet been tested in application in large engines until Audi and Nissan used CVTs for V6 engines. To say that CVT has been around a long time and its reliable is not quite correct, as there has never been a belt driven CVT with the capacity of the Murano's Xtronic unit before. Nissan has an Extroid toroidal CVT which is fluid driven I believe, but it does not have good performance in cold weather, so Nissan opted for a conventional CVT in the Murano.
Like it or not, we are taking a risk by buying a car with this new application of technology. However, it appears at this point that the CVT isn't entirely a timebomb since only a few people have reported failures.
CVT technology has been around for a while, but it has not yet been tested in application in large engines until Audi and Nissan used CVTs for V6 engines. To say that CVT has been around a long time and its reliable is not quite correct, as there has never been a belt driven CVT with the capacity of the Murano's Xtronic unit before. Nissan has an Extroid toroidal CVT which is fluid driven I believe, but it does not have good performance in cold weather, so Nissan opted for a conventional CVT in the Murano.
Like it or not, we are taking a risk by buying a car with this new application of technology. However, it appears at this point that the CVT isn't entirely a timebomb since only a few people have reported failures.
Joined
·
1,437 Posts
Also note that there are several different types of CVTs. The CVT in the Murano is a push belt type. Does anyone know if there are other push belt style CVTs?
Joined
·
83 Posts
there was just an article in road and track called CVTs are coming of age. They said the cvt has been around for about a century, but only in actual application on cars for about 30 years. It has been on numerous other vehicles before that though.
How do you explain CVT to laymen?
Okay, since we now have a new CVT thread to pump, let me ask, how do you explain CVT to people who are not familiar with the concept?
I have an acquaintance who seems to be having a difficult time grasping the concept of "not having gears". Last time he rode in my car, many months ago, we got into a discussion comparing sticks to automatics, and I tried to explain that I don't have gears in my transmission. It went like this:
"okay, but you do you have to push in a clutch and change gears?"
>"There are no gears to change."
"Okay, but do you have to do anything to keep the car moving forward besides hitting the gas? No? Then its an automatic."
>"Okay, but realize that I don't have any gears."
"Are you saying that besides manual and automatic transmissions, there is now a third class of transmissions, called CVT?"
>"Yes."
Then recently, we picked up right where we left off. While carpooling to work:
I accelerated to pull up behind and then pass a car.
"Hmm. That was interesting. It sounded like something was wrong with your transmission. Like it was stuck in gear and didn't want to upshift."
>"Oh boy, here we go again. We went through this last time, I don't have any gears."
So I totally made up this description just to give him something to visualize. Even if it was totally off the wall, it still made him get a little closer to accepting that we just don't have gears in our cars. Don't laugh, people. Okay, maybe a little.
"Picture two cones, laying on their sides. They are pointing in opposite directions, but they are side-by-side. They slide back and forth. There is a belt draped between them. As I drive, I need varying amounts of torque. The CVT constantly slides the cones back and forth to ensure that the right combination of diameters is attained to provide the torque that I need while optimizing the workload on the engine."
Luckily I was able to finish that description seconds before getting onto the highway. I took the opportunity to show him a 20mph to 80mph acceleration while holding the tach at about 3k before it started to fade in the low 2's.
>"See? N-O G-E-A-R-S"
"Yeah, that's pretty amazing."
We'll see what happens next time we get together and he rides with me. Finally, does anyone else get a little freaked out when they hear an automatic shifting (or see it on the tach?)
Okay, since we now have a new CVT thread to pump, let me ask, how do you explain CVT to people who are not familiar with the concept?
I have an acquaintance who seems to be having a difficult time grasping the concept of "not having gears". Last time he rode in my car, many months ago, we got into a discussion comparing sticks to automatics, and I tried to explain that I don't have gears in my transmission. It went like this:
"okay, but you do you have to push in a clutch and change gears?"
>"There are no gears to change."
"Okay, but do you have to do anything to keep the car moving forward besides hitting the gas? No? Then its an automatic."
>"Okay, but realize that I don't have any gears."
"Are you saying that besides manual and automatic transmissions, there is now a third class of transmissions, called CVT?"
>"Yes."
Then recently, we picked up right where we left off. While carpooling to work:
I accelerated to pull up behind and then pass a car.
"Hmm. That was interesting. It sounded like something was wrong with your transmission. Like it was stuck in gear and didn't want to upshift."
>"Oh boy, here we go again. We went through this last time, I don't have any gears."
So I totally made up this description just to give him something to visualize. Even if it was totally off the wall, it still made him get a little closer to accepting that we just don't have gears in our cars. Don't laugh, people. Okay, maybe a little.
"Picture two cones, laying on their sides. They are pointing in opposite directions, but they are side-by-side. They slide back and forth. There is a belt draped between them. As I drive, I need varying amounts of torque. The CVT constantly slides the cones back and forth to ensure that the right combination of diameters is attained to provide the torque that I need while optimizing the workload on the engine."
Luckily I was able to finish that description seconds before getting onto the highway. I took the opportunity to show him a 20mph to 80mph acceleration while holding the tach at about 3k before it started to fade in the low 2's.
>"See? N-O G-E-A-R-S"
"Yeah, that's pretty amazing."
We'll see what happens next time we get together and he rides with me. Finally, does anyone else get a little freaked out when they hear an automatic shifting (or see it on the tach?)
Joined
·
2,243 Posts
Re: How do you explain CVT to laymen?
I have found that the simplest way to explain it is like this:
A "normal" transmission has a series of gears. On one side there is simply one gear. On the other side, you have a series of 4-6 gears with different sizes. You adjust torque by selecting which size of gear you apply. With a CVT, just picture two gears, one on each side. BOTH of these gears, however, can vary their diameter dynamically.
This actually seems to work quite well to explain the concept, which is nice since that's exactly how "our" CVT works. But then be ready for some more technical questions, like how the "gears" change diameter and whatnot.
It is kind of fun to see the look on their faces when they finally understand such a simple concept...
~ Corin
That is the simplest form of a CVT. I found a video of exactly that. The cones stationary, pointed opposite directions, one has power applied to it. A belt is looped over them to drive the other cone. If you keep the RPMs constant on the powered cone, you can vary the speed of the driven cone simply by sliding that belt back and forth.EasternPA said:
I have found that the simplest way to explain it is like this:
A "normal" transmission has a series of gears. On one side there is simply one gear. On the other side, you have a series of 4-6 gears with different sizes. You adjust torque by selecting which size of gear you apply. With a CVT, just picture two gears, one on each side. BOTH of these gears, however, can vary their diameter dynamically.
This actually seems to work quite well to explain the concept, which is nice since that's exactly how "our" CVT works. But then be ready for some more technical questions, like how the "gears" change diameter and whatnot.
It is kind of fun to see the look on their faces when they finally understand such a simple concept...
~ Corin
Joined
·
1,437 Posts
It's very much like a snowmobile transmission, only computer controlled.
Something I realized a couple of days ago, is that the programming mostly acts like a normal automatic transmission, only with 211 ratios. You floor it, it goes to redline, then "shifts" to the next ratio. Which happens to be so close to the one your at, you don't feel the shift. When you let off on the gas, the transmission "shifts" into the most efficient ratio.
Something I realized a couple of days ago, is that the programming mostly acts like a normal automatic transmission, only with 211 ratios. You floor it, it goes to redline, then "shifts" to the next ratio. Which happens to be so close to the one your at, you don't feel the shift. When you let off on the gas, the transmission "shifts" into the most efficient ratio.
Joined
·
2,243 Posts
Where did you find this data?Tyler_Canada said:
It would be so cool to have it display which "ratio" it is in. For example, when using the SE "tip-tronic" style shifting it displays 1-6 depending on which "gear" you are in. Can you imagine having it constantly showing you which of the 211 "gears" you are in? :2:
~ Corin
Regardless of how it works, I love having power transferred 100% of the time. That much I do know! No pauses while it overrevs during shift and then a kick in the back as another gear comes in. Just a nice, smooth, "relax, I'll get you there" feel to it. One gear from 1 to 100.
Joined
·
83 Posts
the article in road and track had a very informative description of the Van Doorne (sp?) concept and modern CVT's. Can't remember which issue it was, only that it had the Carrera GT on the cover. And also remind the person that not all CVT's work on the same principles as the MO's. Check out the Prius tranny to see what i mean.
heres the article:
http://www.roadandtrack.com/article.asp?section_id=20&article_id=1077
heres the article:
http://www.roadandtrack.com/article.asp?section_id=20&article_id=1077
1 - 14 of 14 Posts
Join the discussion
Join now to ask and comment!