Towing a CVT

Mate of my brother has bought a 94? Metro 1.4 auto. Don't ask. Except it is very low milage and not been used for years - executor sale. Body and
interior as new.
Has asked bro to tow it the couple of miles needed. But something at the back of my mind says you can't tow a CVT at all - unlike most autos where it might be OK for a short distance taking it slowly.
Engine won't start. What injection does one of these have?
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Executor sale? I'm guessing the body isn't in great shape unless embalming has been involved. ;-)
Tim
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On 19/11/2018 15:01, Dave Plowman (News) wrote:

definitely not to be towed with the front wheels on the ground (no idea why). Common fault on an injected metro is pump or pump wiring failures, particularly if they stand for a few years. Fuse 17 is for the fuel pump.
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At the back of my mind, it may be something to do with the centrifugal clutch. Although I've no personal experience of CVTs.
Thanks for the tip about the pump. I presume it should run for a couple of seconds when you switch on to prime the rail? Should you be able to hear it doing so?
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On 20/11/2018 14:02, Dave Plowman (News) wrote:

Yes, as usual it should run up pressure then stop. If things are ambiently quiet it should be audible. There can be problems with the immobiliser, when you get in, the alarm warning light should flash, pressing the fob remote left button should stop the light flashing, then turn on the ignition. If the light is flashing then you get nothing except dashlights. If the light is out and the car spins normally then confirm it is fuel by spraying in carb cleaner or easy start into the air inlet hose.
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On 20/11/2018 14:02, Dave Plowman (News) wrote:

Metro had a clutch plate, they couldn't afford the loss of a torque converter. Conic pulleys and belt (push or otherwise) use hydraulic pressure to move a flange and control the gap between the pulley flanges. Wider gap allows the belt to move to smaller diameter, narrow gap makes the belt ride up to a greater diameter. The other pulley is loaded by a spring and the two flanges move apart as dictated by the belt and diameter is contrary to the control pulley. The hydraulic control pressure is produced by a pump. That pump has to be running so it's on the engine.
A long way down this page. http://www.bluebird-electric.net/blueplanet_ecostar/be_4_dc_50_electric_sports_car_bluebird_cartridge_exchange_system.htm
And all is revealed. The Metro CVT has an epicyclic gear on the input. This has 2 clutch packs, forward and reverse. Like the CVT pulley this depends on oil pressure to operate the clutches. Without oil pressure the clutches will drag and wear.
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On 20/11/2018 23:13, Peter Hill wrote:

Fascinating, I never knew about that. One of the kids had an old Metro but iirc that had something very like a traditional Mini engine and gearbox. This looks rather like the system on the old DAF. Thinking about it, perhaps this was after the Leyland/DAF merger in goods vehicles so perhaps it *is* the old DAF system.
There's something similar in my Honda Jazz Hybrid (which is a delight to drive). But that uses a metal chain with links shaped to fit the V-grooves. And expensive transmission fluid!
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On 21/11/2018 12:40, newshound wrote:

The older Metro auto and Mini used a tourque converter and epicyclic box that in some ways was pretty conventional, but quite ingenious in it's packaging, and like a manual Mini/Metro box, it used engine oil.
https://en.wikipedia.org/wiki/AP_automatic_transmission
http://www.austinmemories.com/styled-105/index.html

I suspect it was driven by the fact that they no longer used the A-series engine, and I think (but I'm not sure) that it may have been a Honda unit.
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The auto as used with the A series engine was made by AP. IIRC, it didn't have a normal torque convertor, but something more like a fluid flywheel. Same idea as you have on pre-select boxes.
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On 21/11/2018 16:03, Dave Plowman (News) wrote:

It *did* have a proper torque converter - albeit of an unusual design in order to be in and out at the same end, with the transfer gears being between engine and torque converter. The transmission itself used a system of bevel gears - rather than conventional planetary epicyclics - severely restricting the choice of ratios. The whole thing shared its oil with the engine (just like the manual transmission) rather than using ATF - which was less than ideal.
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Odd. It's a long time since I've driven one, but it didn't seem to have the same sort of torque convertor effect as other autos of the time.
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On 21/11/2018 12:55, Chris Bartram wrote:

Later Metros (mostly badged 'Rover') used K-series engines. The manual versions used Peugeot gearboxes. I wasn't aware - until this thread - that there had ever been a CVT auto. According to Wikipedia, this was a Van Doorne VT-1 unit (as per DAF).
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I had no idea it was a CVT either until I Googled it. They were certainly the fashion for a while - but does anyone use them these days? I'm guessing a robotised synchro box is the norm now for small engined autos.
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On 23/11/2018 01:01, Dave Plowman (News) wrote:

https://www.nissan-global.com/PDF/tcvt_e.pdf
Many Nissans are available with CVT. They use a toroidal variator on larger models and push belt on small cars.
Sadly they a "manual" mode that has caved under idiot consumer / motoring journalist pressure to using "stepped" transmission where the Continuously variable transmission only has 6 or so discreet ratios. This stops the CVT from holding the engine at max power rpm under foot mashed to the floor acceleration and severely impacts the acceleration times by accelerating at less than MAX power.
The only reason to apply less than max power when max acceleration is demanded is if the wheels are spinning.
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I think it is more down to durability. Most CVTs seemed rather short lived. Remember a pal buying a Focus (IIRC) with a broken one cheap, and replacement costs - even secondhand - were uneconomic.
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On 23/11/2018 07:56, Peter Hill wrote:

The Extroid transmission described in the article uses the same principle as the short-lived Austin-Hayes transmission http://www.austinmemories.com/styled-23/index.html of the 1930's.
My colleagues at Rover revived the idea in the 1970's but, even with the much improved oil technology couldn't make the thing work reliably, and it never went into production. The oil needed to be able to transmit very high forces between the discs and rollers without any actual metal to metal contact - and they never really succeeded with that.
Nissan is claiming the world's first successful implementation of this technology. Let's hope that they are right!
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On 23/11/2018 11:50, Roger Mills wrote:

They have been making them for over 15 years.
The traction fluid is more like that found in viscous limited slip differentials. Like a "silly putty" but more fluid, it's fluid but it thickens under shear to transmit the force.
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On 23/11/2018 01:01, Dave Plowman (News) wrote:

Oh yes, Honda Jazz has CVT option at least on the hybrid. It's a very elegant "lump". There's a single multipole motor generator directly attached to the crankshaft which can do three things. It replaces the alternator. It works as a starter motor (off the storage batteries) so you get a very smooth, quiet instant start if the engine has turned itself off at traffic lights etc. And it provides the hybrid "assist", a bit like KERS in Formula 1. Only about 13 HP iirc, and not a "proper" hybrid like the Prius.
And, on top of that, it has a metal belt CVT.
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The older Metro auto - with the A series engine - used a more conventional 4 speed epicyclic auto. The 'new' Metro, a CVT, as you say similar to DAF.
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Don't think any CVT has a torque convertor?

Pretty well like any auto. Without hydraulic pressure, no drive. And since most pumps are engine driven, no oil circulation when towing. (Some older autos had two pumps - one engine driven, and one from the propshaft - which allowed them to be tow started.)
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