[nbr]

Originally Posted by Mpower

I think the Teana might be a CVT too. Nissan is betting really high on CVTs and also make some of the best CVTs in the world.

I test drove a Murano V6 with CVT auto and was simply blown away by the performance and refinement. There is absolutely no rubberband effect and throttle response was really good as well. My opinion on CVT has completely changed after that drive.

I drive a Nissan Maxima 3.5ltr V6 290HP with 6 speed CVT . I love the response i get from my engine and you can feel the sound of the V6 when you rev hard. Out of the many cars i test drove, Nissan have mastered CVT's.

[Mindgrinder]

Originally Posted by sgiitk

@mindgrinder: Yes and no. I was more bothered by the minimal change in engine note as the speed goes up or down. This audio clue is critical to many drivers. Going up and down will depend a lot on the terrain - if you go up the ratio will go down and more revs for the same speed. At least you will notice that you are on an upslope.

These days you are seeing the CVT make a comeback in many ATs with manual over-ride. The manual mode simply uses some predefined ratios.

agreed, for some drivers it is. But for me it hardly matters as i listen to music (loud) at most times. But yes it sometimes make tough to judge during some heavy pulling...but considering the indian market i think CVT's would be great.

[Mpower]

Originally Posted by nbr

I drive a Nissan Maxima 3.5ltr V6 290HP with 6 speed CVT . I love the response i get from my engine and you can feel the sound of the V6 when you rev hard. Out of the many cars i test drove, Nissan have mastered CVT's.

Nice car..
Do you have paddles? CVT doesn't have finite # speeds but can be programmed to behave that way.

[mallumowgli]

Originally Posted by amit_purohit20

I feel the CVT technology at present is still in the nascent stage. Reliable,Efficient CVT's have not yet been designed for high torque and power requirements other than passenger cars like trucks,buses etc. Many of the CVT's are friction driven like Torroidal CVT's or Belt and pulley types. Positive steel belt CVT's have been designed but it still have lot of relative movement between the parts in contact leading to higher wear and other problems.

Wont slip be a more worrying issue than higher wear - thus making it less efficient in reality, though theoretically it may be more efficient in converting torque.

Excuse the newbie question

[.anshuman]

Originally Posted by Mpower

Nice car..
Do you have paddles? CVT doesn't have finite # speeds but can be programmed to behave that way.

Just the way it's done in the Mitsubishi Outlander. The Outlander comes with pre programmed shift points to be used with paddle shifts. The CVT in Outlander is not bad at all.

[KMT]

I have been driving Autoboxes for about 15+ years now (in Oz) and my personal experience with a CVT is far from satisfactory. I currently own a Nissan Murano 3.5.
-There is a significant time lag between accelerator input and engine speed translating to road speed.
-The mileage is extremely poor (5-7kmpl)
-You dont feel connected to the car at all.

The Japs have been dabbling with CVT (since Subaru Justy days in the late 80's) and the Germans (PDK, SMG, DSG etc) have gone down the double clutch path.

ZF seems to be the manufacturer of choice on 'conventional' units with almost every major premium manufacturer using their GB which has a currrent max of 8 speeds.

Personally I believe that DSG will be the way of the future.

[.anshuman]

^^ The new eight speed ZF transmission offered on most luxury cars these days is very close to Dual Clutch box. Then it also comes with a Torque convertor which locks up to provide DSG like characteristics.

I have been driving the Laura DSG for last few months. The DSG 'box is so good that it takes all the pain of urban driving whilst still retaining the Fun to Drive factor. The only downside is lack of torque convertor.

[KMT]

Hi anshuman
You are correct that the ZF is close to a DSG in but in reality the lock up torque converter does the job of the dual clutch, so technically it is still a slushbox.

I have driven a Maserati that had the ZF 6 speed, it was very nice and I thought that that was good, however recently I drove a friends Skoda Superb 3.6L 4WD with the DSG box, the urgency of the shifts was jaw dropping!
I am sure I cannot change gears that quickly and smoothly. From a driving perspective the only downside was that it faltered for a second or so each time from a standing start.

Given the convenience of an AT box I reckon the Indian market has been burnt by past half hearted AT attempts, otherwise it would have been much more popular.

With the DSG I am sure you enjoy both performance and Fuel economy in your Laura.

[.anshuman]

^^ I drove the Jaguar XF Diesel some time back, it comes with 6 speed ZF unit. I thought a conventional AT can't get better. Then i drove the 5 series which comes with the newer 8 speed AT, it was even better. In D mode both the transmissions were as good as the DSG box(maybe even smoother), but as soon as i tried the S mode they still were not a match for the Rapid shifts of DSG 'box in my Laura.

Back to the topic- Any idea about the manufacturing costs of various kinds of Automatic Transmissions? i Guess CVTs are cheapest and Dual Clutch units most expensive.

[sgiitk]

I have been driving ATs since 1999, in Mera Bharat Mahan - first a Zen, then a santro and now also a Civic. I am most satisfied with them even though the first two are/were basic ATs.

As for the CVT I remember a proposal to manufacture a DAF (later Volvo) in the early 1960s which had a CVT. Nothing came of it.

The CVT has evolved over at least 50 years and should be light and reliable. No issued there. vary early CVTs used rubber belts so were limited to lower power engines only.

[Abhi_Automobile]

The only downside is lack of torque convertor.

@anshu:- How is that a disadvantage? This is for my understanding.

I have a clear take on auto-boxes:

I like autos for the convenience they offer. But only if they are a high tech units. For e.g. Dual clutches: VW, BMW, Fiat, Porche, Ferrari, Merc are all migrating to dual clutches; think and fast. Even humble Ford and Hyundai have their iterations of dual clutches which they are in the process of providing in 'common' cars.

However, are most of the conventional torque converter boxes really good? I am not so sure. They are typically slower, costlier and offer poorer fuel efficiency. I was also surprised by the number of fans of i10 auto that we have on the forum. I have driven the car and found it to be really SLOW. I drive a regular G series Swift and expected better response from i10. Similarly, the Verna auto is horrible too (absolutely poor). On the other hand, some cars like CIVIC (and I am sure City too) do satisfactory a job, despite having a slushbox. I've driven auto CIVIC and found it satisfactory. It cannot match the Laura DSG on anything, though.

Basically, I am really keen to buy and auto but only if there is a good auto box in it, not merely for the sake of convenience. The only downside is: Dual clutches are quite costly.

[.anshuman]

Originally Posted by Abhi_Automobile

@anshu:- How is that a disadvantage?(Lack of torque convertor in DSG) This is for my understanding.

With Turbo Diesels the Torque Convertor helps to hide the initial Turbo lag. So in applications with Engines with prominent initial lag, the DSG 'box becomes unresponsive at low revs. An Example was earlier Laura with the PD engine, which had considerable turbo lag. The Current CR engine starts pulling from as low as 1400rpm like most other Diesels do at 2000rpm, so i do not miss the torque convertor much with this engine.

An Example where a conventional Torque converter AT has done a good job of hiding the huge Turbo lag is the Cruze AT. When i first drove this car, i could not believe it's the same car which feels completely dead at low revs in it's MT avatar. The AT has really taken of the driveability issue. It's not that the AT has shorter gearing, it retains the taller gearing and an even taller sixth cog. Overall the AT could have better though.

[amit_purohit20]

@mallumowgli: Yes slip is a big issue with CVT's especially if they are based on the torroidal or rubber belt pulley driven types. The efficieny of CVT's of the Torroidal type has been increased by using special traction fluids which reduce wear between two surfaces by forming a hard film under extreme pressure. The belt driven type CVT have there own load carrying limitations.Basically there are two type of CVT like the Positively driven and the non positive type. Positively driven steel belt with variable pulleys are being used often. The other ones include Non positive type hydrostatic drives(I am not particularly sure how frequently hydrostatic drives are used in passenger cars). The problem with CVT's is designers are still not able to develop a Non-Slip CVT with the simplicity,efficiency,reliability and load carrying capacity of a MT. The day designers are successful MT's will no longer exist except in few cars.

[Guna]

Originally Posted by .anshuman

With Turbo Diesels the Torque Convertor helps to hide the initial Turbo lag.

Torque converters really help even petrol cars with poor low end torque. ATs with torque converter can be driven really slow even on inclines. I wonder how this is achieved in a DSG.

[Mpower]

Originally Posted by KMT

-There is a significant time lag between accelerator input and engine speed translating to road speed. -You dont feel connected to the car at all

-The mileage is extremely poor (5-7kmpl)

How much more do you realistically expect out of a 300 bhp petrol 4wd AT SUV?
My i-10 gives me 8 kmpl.

At the end of the day its an AT without the much hyped about rubberband effect..

Originally Posted by KMT

and the Germans (PDK, SMG, DSG etc) have gone down the double clutch path.

Not true. Audi is pretty gungho about CVT and continues to use it in its A6 and A4. ZF continues to develop some of the best planetary AT in the market.