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I remember the Fiesta and Uno especially with this box. Engine used to rev to high heaven and car would slowly catch up. My aunt had an Escort with one and that needed about three boxed due to belt snap. Do they still have this lag and "slippy clutch" feel?Not driven a recent one.
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>>Engine used to rev to high heaven and car would slowly catch up.
Yes, that's how CVTs work.
It's difficult to get used toif you've been used to more conventional gearboxes, but, allowing the engine to rev near to maximum power is the way to get the best acceleration from a CVT.
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How is this good for economy N.C? The old Jazz seemed to post good figures. I thought having the engine yowling away would hit mpg?
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>>How is this good for economy N.C?
For performance, the engine should be held near its peak power rpm.
However, when you are cruising, for best economy, the engine should be slightly below its peak torque rpm.
The CVT should allow both of these modes of operation, and everything in between.
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However when you are cruising for best economy the engine should be slightly below its peak torque rpm.
I would have thought that depended on whether the engine was at maximum efficiency at its peak torque, but as you didn't state that, I guess I'm wrong?
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>>that depended on whether the engine was at maximum efficiency at its peak torque
In general, it's not far from optimum.
Maximum torque is the engine speed where volumetric efficiency is at its best. Mechanical losses tend to increase with engine speed, so, a speed somewhere just below the engine speed for maximum torque produces good economy.
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Leaving drag out of the equation, yes. But my Honda has maximum torque at 5,800. That's over 120 in fifth. Somehow I think my fuel consumption will be less at 50-70 mph:)
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That's over 120 in fifth.
We are talking about CVTs.
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Still applies to CVT's. Unless they all have max torque at very low revs. On most petrol engines, 4000 rpm for example is around max torque: say 90 mph. Not very economical.
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>>say 90 mph
But, with a CVT, there's no fixed relationship between engine speed and road speed.
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My previous two cars had CVT: the Audi A4 Avant 2.5 TDI was quiet and refined, and never seemed to over-rev, but the Mercedes B200 CDI that followed it was raucous and sluggish - sounding exactly like a London taxi.
I wouldn't have a 4-cylinder diesel with CVT again: I think CVT needs to go with an engine which is either big or refined, preferably both.
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I recently covered 2500+ miles in an A4 1.8 Audi petrol CVT with "flappy paddles" and 8 speed settings on the box.
So it had auto mode, sequential by paddles or the usual quadrant.
Sport mode was available in auto or manual.
This was on holiday with four full sized adults and a mixture of urban, very fast roads and several mountain passes.
I found it very good overall. The only minor problem was a bit of a jolt from stationary to drive but normally it was quite smooth.
The only recent comparison I have is with my current 2.0L Mondeo II auto and the Audi was far superior as was expected.
So to answer "CVTs: have they improved? " The version I used with all its extras must be an improvement in spec and it certainly seemed IMO to drive well .
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The 2.0 litre in the Audi A6 I was driven from Kent to France and Belgium recently, rarely went beyond 2000. I suppose it didn't need to, to get adequate response. 5 up BTW. Didn't seem raucous at any time.
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My Honda Logo has a nice CVT box.
When in 'Drive' setting it generally optimises for good fuel consumption.
If you press 'Sport' it optimises engine power, so tends to keep the revs up more.
Yes, they can feel odd at first, because the engine goes to optimum revs and stays there, so it feels like you are slipping the clutch until you get used to it.
Pretty good to drive - although the takeup from rest isn't as smooth as a Torque
Convertor box, because it does have an (automatic) clutch.
Fuel consumption round town is excellent (45mpg from a 1.3 engine).
It's well over 50mpg on a run.
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The Mk1 Honda Jazz with CVT box is brilliant - the first small auto I've driven that made me think manual gearboxes are on borrowed time.
Hence the consternation expressed by many when it was ditched on the Mk2 for an automated clutch, just to squeak under a tax band (which might get ditched anyhow).
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I have had my A4 2.0 petrol CVT for 6 years and there is nothing high-reving about it. It sometimes even reaches 2500 revs.
Occasionally put it in manual to exercise the engine.
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I've driven the Nissan Qashqai CVT. It's got a small torque converter so the auto clutch problem is avoided and produces most of its power fairly low down the rev range. 80 mph at 2500 rpm is easy. It is a different drive from a conventional auto.
If you want to see a 3.5l Nissan CVT at work there are some posts in you tube with the rev-counter at red line and the speedo seamlessly catching up.
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Link to Nissan Altima 3.5 V6 CVT doing its stuff
tinyurl.com/5fkjze
Enjoy.
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Link to Nissan Altima 3.5 V6 CVT doing its stuff tinyurl.com/5fkjze
Someone accelerating in the dark up to 120mph, while the driver's view of the instruments is obscured by a camera. I hope the driver wasn't actually holding the camera, but even if the camera was somehow fixed in place, this looks to me like someone trying to win a Darwin Award.
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I would never criticise anyone's driving, NowWheels, but when I'm doing a pedal to the metal from rest to as fast as I can, I tend to look at what's around me rather than at the instruments which, over 20 seconds, aren't really going to be worth checking.
Best I've done so far in the Darwin Award is third.
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Man will never adopt what he doesn't understand. They walk around blind in their folly. This folly was shown by the luddite fools in a sinister plot that banned said perfection from F1 which was most greatly lamentable. But we decry change, we cling on to an invention dreamed up by 17th century button maker. Bring on the gas turbine bring on the regenerative electric motor. We deserve new technology. "There are more things on heaven and earth that are dreamt of in your philosophy" said Quntin Tarantino when he wrote Basic Instinct.
I have lurked and watched this site for a while and smiled, I take the path to contribution with unease for I am but a shy man. I may post again.
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HJ praises the CVT fitted to the Toyota IQ.
Only one I've ever driven was a DAF/Volvo Renault-engined rubber band job. Never got completely used to it but it drove interestingly and made a charming whistling noise on the overrun. Some recent small FWD applications have used steel link belts and been troublesome I understand.
Of course as NC says a CVT that works as it should, and is decently durable, is theoretically the ideal transmission for a petrol-engined car.
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Verily this man speaks the truth. Have no fear NowWheels, calm down my dear. Soon enough the machine will persevere in collaboration with motor industry inautomated cars so we will not be driving at all. Apart from the grievous interference in ones life this has some good points. Instead of the increasingly tedious job of driving I will be able to practice Yoga, joints permitting whilst reading L Ron Hubbard.
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Instead of the increasingly tedious job of driving I will be able to practice Yoga joints permitting whilst reading L Ron Hubbard.
If you plan to read that stuff, I'm relieved that you won't be driving ;)
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You are another night owl like me my dear NowWheels. There is one phrase of L Ron Hubbard that is good for my planned in car yogic meditation which one will need in the dark days of coming automation.
"I have seen life from the top down and the bottom up. I know how it look both ways"
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