Renault Fluence with CVT

[Belatti]

Renault is manufacturing the new Fluence here in Córdoba, Argentina.

In the Renault webpage it says that the model brings a CVT transmission option.

After searching a little bit, I found that its a couple of pulleys with a steel belt. Im wondering if our European fellows know this Fluence and if it has been sold in Europe, is it reliable? Has the fuel cons been improved comparing it with the 6 speed manual version?

[autogyro]

It is a Van Doorne CVT of conventional type using a linked chain and two pulleys.
Like all CVTs and TVTs it uses energy to maintain the position of the pully diameter actuators.
It is said to be more efficient than their conventional four speed auto and may be more efficient than their twin shaft unit.

However driving a CVT with pulleys is similar to driving a rubber banana.

This type originated in the Daf Variomatic and ended up in some Fords and Volvos with the chain instead of a belt.
It also formed the basis of the Williams F1 CVT.

Over 30 years old.

[Belatti]

OK, first of all thanks for the info Autogyro.

Now allow me to say that I dont share your disdain for everything thats old technology. The wheel is old technology and we don´t go saying we should be driving magnet levitated cars all the time.

It would be nice if someone can post a pic or a dagram for the Renault CVT installation.

[autogyro]

I do not remember displaying any disdain for old technology Belatti.
I simply said it is 30 years old.
In fact apart from variations on a theme, it is difficult to find anything in motor engineering that is not 'old technology'.

[Arunas]

Technicaly Fluence is based on Samsung Motors SM3 and Renault Megane (latest generation) models. Here in Europe it is supplied from Turkei Bursa factory. CVT (from Nissan, don't know, who produces it) transmission is available as an option for top engine 2.0 16V 103kw (standard is 6 speed manual). CVT has also 6 speed "manual" +/- mode. Can get more info in .pdf format, just don't know, how to post it

[alelanza]

Related to the murano one?

EDIT:

Very similar indeed, here

http://www.jatco.co.jp/ENGLISH/NEWS/2010/100727E.html

Googling brings up a lot of Dodge Caliber results, looks like their forums may have a lot of info on that one

[Arunas]

alelanza, you are right, it's a YATCO transmission, even more popular than I thought before... Renault started using it just couple of years ago. Regarding reliability, opinions varying. I know localy several vehicles clocking over 200k km without problems, so it can depend on driver

[Belatti]

I do not remember displaying any disdain for old technology Belatti.
I simply said it is 30 years old.
In fact apart from variations on a theme, it is difficult to find anything in motor engineering that is not 'old technology'.

OK, sorry for that.

Here I post a diagram showing how it works (thanks Aruna )



At first glance it looks like it cant handle too much torque, but simple & reliable...

[autogyro]

The concept has been sold around the motor manufacturers since the 1960s.
It is fairly reliable now.
You must ask how much energy is used to vary the pulley diameters under drive load.
The answer will explain why efficiency is not as high as first thought.
The main thing you need to do before buyin one is to drive it first.
I think that will change your mind and explain why Ford and Volvo shelved it.

[Belatti]

You must ask how much energy is used to vary the pulley diameters under drive load.
The answer will explain why efficiency is not as high as first thought.

Does it have an hydraulic actuator?

[autogyro]

To be honest Belatti I had not researched the latest JATCO so I cannot be certain but all previous version are hydraulic operation.
The cone system also only gives a fairly narrow ratio range and the JATCO uses a torque converter for direct engagement and to extend the ratio range (other applications use extra gearing).
The result is a strange driving experience that needs the addition of a virtual stepped ratio control system that tends to defeat the object of the exercise anyway.

[lolzi]

I remember some people testing CVT on a kart. The drivers said there was a lot of throttle "lag" - when mashing the throttle to the ground, it took some time to actually get some torque to the wheels. Are all CVTs like that, and if so, why?

[Arunas]

I remember some people testing CVT on a kart. The drivers said there was a lot of throttle "lag" - when mashing the throttle to the ground, it took some time to actually get some torque to the wheels. Are all CVTs like that, and if so, why?

I think it is not throttle lag you are speaking about. Kart has cable operated throttle - this should not generate any lag. Lag in acceleration can be felt due to the time needed for a transmission to move pulleys to change torque reduction ratio. This can be felt on all vehicles using CVT, actually depending on speed this can be even more so in this case, as CVT here uses torque converter and accelerator is drive-by-wire, not mechanicaly connected with throttle. Hope it is possible to understand my english, not enough familiar with it..

[Belatti]

lolzi, I think arunas is right and maybe the driver in a CVT kart can change the way he uses the throttle.

In a way they also suffer lag with "common" kart transmissions but due to 2 strokes narrow engine powerband.

Kart drivers solve this using partial throttle in the corners, specially tight ones to keep continous flow in the carb venturi.