CVT transmissions

[TheOtherLeft]

Even though CVT transmissions are meant to be best thing for auto, are they actually any good? A lot of the newer cars are coming out with CVTs but then again they offer the traditional 5 or 6 speed auto in other models as well.

- Does the CVT have limited power transmission compared to traditional autos?

- Does it require more frequent servicing? Is it more expensive to maintain?

- Are they more efficient then traditional autos?

- What other issues do CVTs have?

Thanks,
Ben

[SCANAS]

Honda used them a lot between 95 and 08 and had a stack of problems with them. So much so they still have a 7 year campaign on CVT so if yours goes within 7 years of buying one Honda will replace it. Honda only offer it on the Hybrid now. And if Honda can't get it right the others have no hope.

You can't rebuild them so you have to go new at about $7000 drive in drive out on a JAZZ, which is a sub $20000 car to start with.

If you buy one do the Auto service twice as regularly as the book specifies.

We had a customer cars come in with a dodgy box quoted her $7000 (before honda campign was on.) Her brother was a Auto Trans expert and said i'll rebuild it. Foreman told him not too, but wouldn't listen. When he was prying the the chain or ban (which is under enormous tension) off it come off with so much force it cut his neck open and he was taken to hospital in an ambo. He called us back and told us what had happened. Poor bloke.

Outlander, Rav4, Colt, Dualis, X-trail, Mini, Civic Hybrid and others are still running them. They give better fuel economy as they are able to sit in the engines sweet spot rather than change up and down gear all the time cutting the throttle putting it back on more to maintain momentum.

Alot of the Honda's are simply the start clutch which is around $1200-$1500 and not the box itself.

What car is it?

[BlueSuzy]

Its a vespa

[turbo gu]

Subaru uses them in MY10 onwards Liberty and Outback and the new Impreza will have one aswell. They are a bit different as they run a torque converter. No servicing of the box. Oil for life Its around $800 for 20l drum.
There was a massive increase in economy using the cvt over the old auto 4/5 litres per 100.
They are odd to drive and a bit noisey.
no real issues yet

[MICK77]

Subaru uses them in MY10 onwards Liberty and Outback and the new Impreza will have one aswell. They are a bit different as they run a torque converter. No servicing of the box. Oil for life Its around $800 for 20l drum.
There was a massive increase in economy using the cvt over the old auto 4/5 litres per 100.
They are odd to drive and a bit noisey.
no real issues yet

My place of employment means I have driven many of these.

They are very fuel efficient.

They are a little slow off the mark but, once moving are quite good. As stated above they are noisy.

DO NOT attempt to reverse up any sort of incline as it simply won't do it.

I had my foot flat to the floor, engine revving, CVT stalling up and moving about 1km/h up an approx. 25 degree incline. You could smell the CVT working extremely hard. I believe the reason for this is when reverse is selected the transmission selects 2nd of 6 preset ratios which is too tall a ratio.

We have a customer who cannot reverse in to his driveway at all.


Cheers,

Micko

[DamTriton]

A bit of lateral thinking would place 2 CVT mirrored over each "axle" (not quite accurate, but to give location), 1 CVT per wheel. Both CVT's could track each other for the gross movement of ratios and you could tweak the individual ratios for a differential type effect.. Doing this for all 4 wheels would give an interesting concept - fully active wheelspeed control with maximised torque. Best of an open diff, LSD and a locker, and a stepless automatic.

[SCANAS]

^^^ I smoke weed every day < Dr Dre

Good idea, Nightmare to do.

[turbo gu]

Subaru uses them in MY10 onwards Liberty and Outback and the new Impreza will have one aswell. They are a bit different as they run a torque converter. No servicing of the box. Oil for life Its around $800 for 20l drum.
There was a massive increase in economy using the cvt over the old auto 4/5 litres per 100.
They are odd to drive and a bit noisey.
no real issues yet

My place of employment means I have driven many of these.

They are very fuel efficient.

They are a little slow off the mark but, once moving are quite good. As stated above they are noisy.

DO NOT attempt to reverse up any sort of incline as it simply won't do it.

I had my foot flat to the floor, engine revving, CVT stalling up and moving about 1km/h up an approx. 25 degree incline. You could smell the CVT working extremely hard. I believe the reason for this is when reverse is selected the transmission selects 2nd of 6 preset ratios which is too tall a ratio.

We have a customer who cannot reverse in to his driveway at all.


Cheers,

Micko

Reversing is not there strong point We have alot unimpressed customers over this. There is a possible fix coming

[tehekho]

A bit of lateral thinking would place 2 CVT mirrored over each "axle" (not quite accurate, but to give location), 1 CVT per wheel. Both CVT's could track each other for the gross movement of ratios and you could tweak the individual ratios for a differential type effect.. Doing this for all 4 wheels would give an interesting concept - fully active wheelspeed control with maximised torque. Best of an open diff, LSD and a locker, and a stepless automatic.

How do the transmissions detect when slip is necessary? Or do these have inherent slip live conventional autos? I didn't think they did (Happy to be told otherwise...)

[DamTriton]

A bit of lateral thinking would place 2 CVT mirrored over each "axle" (not quite accurate, but to give location), 1 CVT per wheel. Both CVT's could track each other for the gross movement of ratios and you could tweak the individual ratios for a differential type effect.. Doing this for all 4 wheels would give an interesting concept - fully active wheelspeed control with maximised torque. Best of an open diff, LSD and a locker, and a stepless automatic.

How do the transmissions detect when slip is necessary? Or do these have inherent slip live conventional autos? I didn't think they did (Happy to be told otherwise...)

Same way that the stability controls vary the brakes - computers, a basic algorithm, and a few sensors/actuators. Wheelspeed could be mathematically correct for all steering angles, ie no wheel slip at all, and no transmission wind up with different F to R speeds.

In answer to your question they do not slip like an auto unless they have a torque converter or viscous clutch.

AFAIK they use a hydraulic ram to push the cones together to vary the ratio, modifying the hydraulic pressure wouldn't be difficult to achieve differential action and/or gross ratio change.

[tehekho]

A bit of lateral thinking would place 2 CVT mirrored over each "axle" (not quite accurate, but to give location), 1 CVT per wheel. Both CVT's could track each other for the gross movement of ratios and you could tweak the individual ratios for a differential type effect.. Doing this for all 4 wheels would give an interesting concept - fully active wheelspeed control with maximised torque. Best of an open diff, LSD and a locker, and a stepless automatic.

How do the transmissions detect when slip is necessary? Or do these have inherent slip live conventional autos? I didn't think they did (Happy to be told otherwise...)

Same way that the stability controls vary the brakes - computers, a basic algorithm, and a few sensors/actuators. Wheelspeed could be mathematically correct for all steering angles, ie no wheel slip at all, and no transmission wind up with different F to R speeds.

In answer to your question they do not slip like an auto unless they have a torque converter or viscous clutch.

AFAIK they use a hydraulic ram to push the cones together to vary the ratio, modifying the hydraulic pressure wouldn't be difficult to achieve differential action and/or gross ratio change.

In your thinking (and mine also) it would be relatively simple to control the transmissions (in a perfect world). I can't see any reason it wouldn't work but my mind is still clouded with the thought that it wouldn't be 'that' easy. Packaging the transmissions would be a whole 'nother beast...

[-Scott-]

In your thinking (and mine also) it would be relatively simple to control the transmissions (in a perfect world). I can't see any reason it wouldn't work but my mind is still clouded with the thought that it wouldn't be 'that' easy. Packaging the transmissions would be a whole 'nother beast...

In an ideal world it would be a great system. In a world which includes Murphy's Law, I'm wondering what will happen when a control system glitch gets the wheels out of sync?

Worst case, travelling at speed, with left & right side suddenly deciding to drive at significantly different speeds, the vehicle would effectively be unsteerable, and those inside would only be along for the ride.

Engineers may be able to reduce the probability of this happening, but the consequences of such an event are potentially horrific.

I wouldn't be signing up to be an early adopter.

[GRIMACE]

Don't know anything about the workings or the longevity of CVTs,
But now that we own a 2010 Lancer with CVT I can safely say I do not like them!

It's noisy, it's slow, and If you do drive it semi hard (ie entering traffic at almost full throttle to about 80k) it smells...

Can't wait for the missus to see it from my perspective and sell it, so I can get a couple more land rovers

[poppywhite]

First developed by DAF in the "60's. only good in small capacity vehicles, supposed to do same speed both forward and reverse, I think it was origionally a rubber belt but more modern japanese is steel belt.
It was origionally dutch engeneering so what do you expect! dykes and all that!
Maybe still neeeds some more developement for hill starts here. Isnt holland a flat reclaimed swamp

[KiwiBacon]

Audi has a gearbox they call "multitronic" which is a 4 speed auto with a CVT "splitter" on the back.
In manual mode it gives you 8 ratios to chose from, in auto it can dial in whatever it wants. The CVT on the back has enough range to span between any of the 4 auto box fixed ratios.

Fuel economy isn't as good as DSG or manual though. 2.0tdi with it uses about 6 litres/100km. Can't get below 5.5 l/100km no matter how much you try.

[RED60]

Isnt holland a flat reclaimed swamp

Much of Holland is below sea level..... so no matter where you wanna go, it's pretty much all down hill....

[nastytroll]

So these are a variation of a leuellen pully? Well sounds just like one to me.