the problem with cvt is the belt reliability, the punto probably isnt pushing the envelope here, and 50K isnt a big mileage. How long they last on big cars is a different matter.
shamless plug for a UK company - torotrak, with a reliable high torque/power capable ivt box using toroidal discs rather than belts. Deals signed with aisin, getrag, etc, testing done with Ford, Land Rover etc. Boosts fuel economy ~20% compared with 6 speed auto. Going to be used in Tractors as well.
Has some fancy tricks that allow high performance, hill descent/climb etc.
www.torotrak.com
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I've been wondering... why do they install a rev counter in a car with a CVT box ? Correct me if I'm wrong here, but the engine always keeps its revs at the same level, doesn't it ?
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I am the only Pole over here.
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My Fiat Punto with CVT has done about 50,000 miles without hitches. I imagine this system is a lot less complex than that of normal auto boxes, so that should be a positive point.
Is the Punto still available with CVT?
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Can someone explain the difference between CVT and "conventional" autoboxes?
And before Dalglish comes and says I can find the information myself, I could, but I'd rather have someone I 'know' explain it to me in terms I can understand. I thought CVT was super duper but that comment about Micras has confused me.
Cheers,
(Bear in mind, I only found out a short while ago what a torque convertor was).
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Adam
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Adam,
Here's my attempt to answer your question - it's a huge subject though...
A conventional automatic has a finite number of ratios. Instead of a clutch* there is a torque convertor. When in neutral, there is no connection between the input and output. The torque converter is a really clever bit of kit - it increases the flexibility of the gearbox to the extent that it is reckoned to give the equivalent of an extra ratio.
A CVT allows a stepless change between ratios, there are, in effect an infinity of gears. This raises the possibility of having a geared neutral. This can give immense problems for the design of the rest of the downstream drivetrain because at very low ratios, the torque can be massive!
There are many competing CVT ideas - not surprising really because the possibility of always being in the best gear, for either acceleration, or economy depending on driver demand is worth the cost and effort to develop.
I applied for a job at Torotrak in Leyland a number of years ago. For a number of reasons, none of which being suitable for publication, I decided against. It will be interesting to see if their technology ever becomes as popular as the idea itself deserves.
I have just read about a new (to me at least!) idea to have a CVT with two parallel load paths through the transmission, one via gears, the other via a generator/motor pair. I think this has real potential because it is not reliant on any rolling contact used for transmitting power.
If the rolling contact slips significantly, then the typical CVT rapidly becomes an efficient rotary friction welding machine!!
The transmission of power via a fictional contact between two metal parts is never simple - think leaves on the line!
Number_Cruncher
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Dave and N_C,
Thank you very much. I now almost feel qualified enough to rebuild an autobox ;-)
Thanks again,
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Adam
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On the original subject of durability..As others have said, the CVT has been around a long time. In 1908 Rudge motorcylce co entered a CVT-geared motorbike into the TT - it used a leather drive belt and a hand-operated linkage to vary the diameter of the rear pulley. In the 1920's several German companies exterimented with CVT's using metal belts and they were used in textile factories (to take drive off spiining shafts running through the mill). Then of course there was DAF...
The basic problem with the CVT is that it relies on friction to transmit the power. This is OK at low power & torque levels, but at higher powers then duracbility can be a problem. Once any slip sets in, a lot of heat is generated and the thing wrecks itself in short order.
GM have had a CVT plant in Hungary for some time, but production has been very slow in coming due to problems with the tranmissions. Similarly the Ford/FIAT plant produced transmissions that were bedevilled with durability problems. The ZF unit used in the Mini is also proving troublesome and many owners are on their second or third transmission (this is a problem in the US, where many Minis are ordered with auto option).
Personally I wouldn't buy one.
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My posts must be invisible again. I will try again.
Does Honda manufacture its own CVT?
Is the Punto still available with CVT?
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Maybe no-one knows the answer to your posts.
>>Is the Punto still available with CVT?<<
A quick Google search suggests yes and that they're equipped with a "CVT Speedgear."
>>Does Honda manufacture its own CVT?<<
No idea. Sorry.
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Thank you Adam, some response is better than none, even when the answer is not necessarily known.
If the Speedgear is CVT, then the fuel consumption seems to suffer a bit in comparison with the manual box. At least that is what the figures on the Autobytel site say.
I looked on the Fiat site and for the information but it is a truly awful web site and I gave up eventually.
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It is really poor. Fiat.co.uk was my first port of call and it was dire.
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In general, car manufacturers have dreadful web sites.
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Funnily enough, the Citroen site is not too bad. It is ok for most of the information required.
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Oddly enough, I find the Vauxhall one strangely useful for information. Miles better than the excuse for a site Ford have.
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My posts must be invisible again. I will try again. Does Honda manufacture its own CVT? Is the Punto still available with CVT?
Yes, Honda manufactures several CVT's of its own design. The 'Multitronic', with multiplate clutch is the one used on UK market vehicles, IIRC. Certain aspects are (I believe) still under patent from Van Doorne so I think they buy in some components. Certainly the drive belt looks the same as the one used on the Nissan/Subaru Hyper-CVT.
The Nissan/Subaru is a kind of CVT+tiptronic function. The major components are made by Fuji (parent of Subaru). Nissan also make the excellent Extroid CVT which uses rollers rather than a belt - definitely the way to go for higher output engines.
The FIAT SpeedGear looks very similar in design to the Nissan/Subaru unit (it may even be that unit made under license). The SpeedGear is still being produced - don't know whether it is available in the UK.
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I can recommend Toyota site for info.. Ford I agree is ABYSMAL...
Audi have Multitronic : about 20% plus of A4s have it I believe. Same CVT principles - stainless steel belt etc.. Torque limited to smaller engines .. but range slowly expanding to larger ones...
Torotrack keep threatening to have a commercial system.. Judging by the share price, not a real threat.
madf
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Sorry, I was wrong. The Honda CVT is called Multimatic, Audi's is Multitronic. The Audi system is a little different in that it uses a segmented chain-belt with small 'pins' sticking out to give increased torque-transmission capability (that's the theory, anyway).
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The Multimatic is the standard transmission on the Honda Jazz/Fit in Japan. There have ben a few reports re the oil-bath clutch, but these sem to have been few. The only "factual" info I hjave seen is this:
"Yes, this is why it's also called the 'start-up clutch'. Failure of the start-up clutch has become a sort of a 'legend' around the ASEAN region, because of rumours originiating from a few cases. In Malaysia for e.g., the rumours are flying around so heavily that the outsider might be forgiven for thinking that the CVT gearbox is a design failure but when I checked with Honda Malaysia for e.g., they reported less than 20 warantty claims for Jazz and City combined. This is from a total of around 20,000 units sold."
from this thread: www.vtec.net/forums/one-message?message_id=380654&...1 on "The Temple of VTEC" site. Good information on the Jazz engine etc: on reflection, more than enough!
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I drive a 96 automatic Primera. I am aware that some of the later models are CVT. How would I recognise a CVT Primera?
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CVT's can be coupled to the engine using one of three techniques: electromagnetic powder clutch; conventional friction clutch (wet or dry) or hydrodynamic coupling (some kind of torque convertor). Nissan have used all three at some time or other. The problem with the TC is that it is diffiult to completely 'uncouple' it, so there is always some creep.
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Thanks HJ
I am now CVT averse. How would I recognise a CVT automatic gearbox?. Would I have to find the spec for the model. How prevalent is CVT
Regards
John
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I have an A6 2.5TDi CVT (so not a SMALL engine) and it is superb.
I have done 63,000 miles in the car and no problems. Fuel economy is as good as the manual, as is 0-60. CVT suites a big diesel as it smooths out the narrow power band. If you want to get going you just hit the accelerator and the revs rise to peak power/torque (2,500 - 3,000) and the car just goes faster and faster until you back off. No jerks or jumps, no trace of down or up shift.
The only minor grumble I have is that when pulling of from standstill there is a little hesitancy that you don't get in a regular auto, but I just learnt to drive around it.
Re the comment about there being lots of revs when pulling off; not with this combo of big diesel/CVT. Unless you are racing away the revs don't get over 1500 in town traffic when pulling off, and even on the motorway rarely get over 3,000 (except for the odd Italian tune up)
Cheers all
TimBo
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Yes, Honda manufactures several CVT's of its own design.
Thank you Aprilia.
Some of these transmissions seem to provide little advantage over tranditional torque converters, when it comes to fuel consumption.
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HJ, Ithink you are mistaken about the X-Trail being CVT. I run both a Honda Jazz auto (CVT-7) and an X-Trail auto. The Jazz runs most of the time at pretty constant revs. The X-Trail on the other hand performs like a conventional auto (of which I have owned several, the revs rising and falling as it goes through the gears. Also it has a switchable overdrive very similar in use to a Volvo I ran a few years ago with an Aisan Warner 'box.
Both autos are excellent in their different ways. I am fairly confident about the azz CVT because it is a Honda.
HectorG
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What do people think of the engine note of cars with CVT transmission? I imagine it is strange never feeling the car 'drop' into top gear as in a conventional auto. Using an endless surge of forward motion then presumably trailing off, do the revs drop down when you reach higher speeds?
It doesn't sound very 'relaxing' but perhaps is more subdued in diesel applications. I have recollections of the Fiesta CVT efforts of Ford in the 90's with their constant revving engines akin to a slipping clutch.
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When we tried the Jazz CVT, the engine ran at peak torque (about 2800rpm) and was very different to the old Daf thing! Seemed to pick up easily, with 3 aboard. If you want, you can select the 7-speed gadget and flick up and down to our hearts desire. Apparently it will also run in a similar way to a conventional auto box if you don't want to use the paddles: shifts among the 7 choices according to throttle setting. Didn't bother with that.
We're seriously thinking of a Jazz, but need to try the ride out for an extended period. Most of the roads here (Ribble Valley) are twisting, lumpy, and off-camber, all at the same time.
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My wife has doubts about the seats in the Jazz. If you want to test out seats and ride quality, take someone with a bad back, as they can usually make a realistic assessment within 30 minutes.
Other than that, we were both very impressed with it.
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We, until recently, owned a Volvo 440 CVT. When they're working corectly they're good to drive (economical and relatively fast). However they're not reliable gearboxes as they tend to shudder (and sometimes stall) when moving from P into D with your foot on the brake and when coming to a sudden halt eg lights or junction. I gather Ford used a similar gearbox in the Fiesta and Escort in the 90s and gave up because of the repair costs.
They're not thought well of in the trade ("not a proper automatic is it" etc).
We were considering replacing the Volvo with a Honda HRV CVT. When I rang to make enquiries I was told that all the HRVs with this box had had recall work done and were OK. Even though it's a Honda I would question the longevity of the box.
Unless you really prefer the driving characteristics of the CVT over a conventional 4 speed auto I wouldn't bother until long term reliability of these new CVTs is known.
Regarding how can you tell CVT, it usually doesn't have 1 and 2 on the box, only D and L. When driving, the revs bear no relation to road speed and the box does not change up when you put your foot down.
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The transmission of power via a fictional contact between two metal parts is never simple - think leaves on the line!
Is that because it does not exist?
Sorry,could not resist.
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>> The transmission of power via a fictional contact between two metal parts is never simple - think leaves on the line! Is that because it does not exist? Sorry,could not resist.
Sierraman,
Sorry, I don't understand what you are getting at (I'm possibly being a bit thick or humourless) - could you explain?
Number_Cruncher
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Why is what I am copying off a previous post not appearing in mine?
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Why is what I am copying off a previous post not appearing in mine?
It's because you're removing the default ">>'s" that automatically get generated when pressing the "quote original message" button and substituting in your own. For reference, by putting the 'less than' symbol at the start, and 'greater than' symbol at the end makes the words you've quoted invisible in this forum.
DD.
ps, I've sorted out your other post, btw.
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Just missing "the Strange case of the missing R" methinks.
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Ha ha, I hadn't noticed that!
Number_Cruncher
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