CVT Transmissions - Opinions Please!

[ToroTVR]

Has anyone out there had experience of or own/owned a vehicle with CVT (continuously variable transmission) like the new Audi system for example, if so what are your opinions of it, what is it like to drive, is it better on fuel etc? All opinions welcome.
Cheers. Andy.

[go-go]

As an apassionate I can't be objective. But, reliability continues to be a problem, it wastes a lot of energy due internal friction, and that horrible sense of consumed clutch in automatic mode. The "Emulation" of gear change is quite pathetic. No I don't like it.

[Bodo]

I have driven a new generation CVT in a test vehicle at the university.
It was a std. diesel car prepared by the CVT-manufacturer for evaluation and test purposes.
We drove 16000km in three weeks: acceleration was 17% better, while fuel consumption went down 6% (average).

Ratio of the box was about 6:1, the pulleys were guided by hydraulics, and there were sensors at the incoming and outgoing shafts. The ECU of the box has, of course, been adjusted to the engine's data.

As you can see, it has nothing to do with DAFs, ROVERs, HONDAs or AUDIs CVTs. It was just the thing you will find as an option in near future's cars, and I must say, there will be no better transmission available!
The engine's sound is a bit confusing, because the car accelerated like sh*t of a stick, and revs didn t change.

[ToroTVR]

Bodo,

Very interested to hear about this new type of transmission, is it the Torotrak IVT ( Infinately Variable Transmission ) currently being developed for BMW by Getrag? If not I would be very interested to hear more of this as I have an interest in the transmissions of the future.

Cheers, Andy.

[davidy]

I had an Audi A6 1.8T Multitronic for a couple of days while the A8 was being serviced. Initially I found it a bit weird, but after a time I grew to quite like it. It was very smooth and very economical (I was averaging 38mpg on normal driving). It tended to keep the revs between 1800-2400rpm and just change gear to suit. Whenever you put it in tiptronic mode to see what gear it thought that it was in, it was always 1 gear higher than you thought (it was a 6 speeder)

Kickdown was a bit violent, but I think this is a feature of all turbo cars with auto boxes, as you get kickdown and boost arriving at the same time!! but acceleration without kickdown was impressive.

I think that it would be really suited to a bigger torquier engine

[pbrettle]

davidy,

Exactly the same feedback that I have heard about the Audi Multitronic gearboxes - of the current crop of CVTs they are the best - bloody Germans again..!

Still, it beats the old problem of autoboxes and fuel / power sapping - they seem to have got it licked. The only problem that I have heard is that they are having problems putting them on the TDI Audis. Something about a limit to the torque they can take which means that they cannot be fitted currently - shame as a 15%-20% increase on one of those things would be quite amazing. Had a A4 TDI 110 for a short while and I was averaging 45MPG on the motorway (at legal speeds of course) and 55MPG when doing 55 - 60!!!! Quite stunning really.

Cheers,

Paul

[Fatboy]

I'd always heard that CVT transmissions can't cope with large amounts of torque? Does this new system overcome that or is it a totally new approach?

[davidy]

I was gobsmacked at the ecomnomy that I achieved with the A6 1.8T multitronic and being German they will make it work on higher torque engines. I believe that it is offered as an option on 1.8T and 2.4 A6s (and A4s?)

But then again I also get over 30mpg out of my Tiptronic 3.7 A8 on long runs (indicated 80-85mph on motorways), over the last 40 hours it has averaged 28.6mpg at ave speed 46mph, so maybe petrol Audi's are good as well as the oil burners (and yes before I get comments I do use the pedal on the right and the tiptronic box when overtaking on single carraigeway roads)

In response to go-go who obviously is passionate about manual gearboxes, I was until a few years ago (having owned TVRs, Impreza Turbo, etc and I still have one TVR). With a large engine and a good autobox you can make very good smooth rapid progress and can really concentrate on smooth inputs to the other controls (steeering/brakes/etc) so it is just a different kind of driving experience, but for ultimate tactile feel you need a manual box.

[ToroTVR]

Interesting comments chaps! You are correct in saying that belt drive CVTs are limited in the torque that they can handle, however, the Torotrak IVT that I referred to does not use belts and pulleys, it is a "traction drive" transmission using a series of rollers and discs or "toroids" and a special fluid developed by Shell called traction fluid. The main advantages of this system (and indeed the reason for its development) is that it gives (proven in tests!) 28% better fuel economy than a current 4 speed auto and 17% better fuel economy than a manual transmission with better performance and drivability. It also has no limit on torque and is currently in the final stages of development for the US SUVs which have anything up to 7 litre V8s, Ford & GM are developing the Torotrak system and have been doing for 6 years plus. The Torotrak system is also being developed by two leading HGV manufacturers rumoured to be Volvo and Scania. Currently the series 4 gearbox is being developed for front wheel drive cars, the factory have a Ford Mondeo fitted with one and this gives amazing fuel economy!! By the way Torotrak is a British company based in Leyland, Lancashire. Have a look at their website to see how it works, there are some very nice colour diagrams and a superb explaination of how it works etc. Look at www.torotrak.com by the way I do not work for them!!!!
Andy.

[philshort]

I've driven a Micra with CVT (my mums). Goes well for a 1.4, but the slipping clutch sensation does nothing at all for me sensibilities. Not sure how they work out more economical, it revs its balls off if you even think about depressing the accelerator pedal.

[bodo]

@ToroTVR
Sorry for delay.
Unfortunately, I can not tell you who is developing the box I have tested, but as soon as I could, you'll read about it in the official news of a german company ;-), if it is not already published yet!

Some data makes it an interesting alternative for manual boxes: max. torque allowed: 400Nm (dont know in [lb ft], sorry) and efficiency is between 90...93%.
It uses pulleys and a sheet metal belt, just like the CVTs already used in passenger vehicles.

I've followed the Torotrak-link; construction looks very interesting, as it seems, that it allows more possibilities for future developments.

[Bruce Fielding]

Once drove a Daf 55... Best thing about it was that it went as fast in reverse as it did in forward! Funny to think that was the precursor of all this techno.