New to me auto.

Just got a car fitted with a 7 speed twin clutch twin layshaft automated synchro gearbox. Which they call a PDK. Last version of this I drove some
years ago was a single clutch type (BMW SMG), which was dreadfully clunky at lowish speeds.
This one when driving normally in town changes just as sweetly as a slush pump type. Although the absence of a torque convertor makes the first few yards from rest not quite so smooth.
Having 7 gears, it has a much higher top gear giving much more relaxed cruising than the previous ZF 5HP. Admittedly an old slush pump box these days, though.
To say I'm impressed would be an understatement. ;-)
The other odd thing is it is programmed like I'd have done myself. Always in the gear I'd be using if a manual. Unlike the previous ZF that couldn't seem to decide which gear to use.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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I thought DSG / PDK type boxes were the future, until I got something with the ZF 8HP.
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Quite - be very interesting to compare the two on the same model. With the same programmers.
The only time I feel the lack of a TC is at very low engine speeds where the TC would even out any slight vibration. Being very picky, though.
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Just to add, I'd guess the epicyclic box would still win out in terms of absolute refinement. Why Jaguar - always known for the best compromise between performance and refinement - probably stay with it. Be interesting to know how the two compare cost wise in manufacture too.
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I think Jag are using the ZF 8HP these days - mind you, who isn't? - and I think the Evoque uses the 9HP transverse application.
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Wonder if there is a limit to how many gears before no added benefit? Must add weight to some extent.
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As we move away from peaky diesels, I think things will start to get a bit more sensible again.
And hybrids really lend themselves to a planetary operation like the Toyota Hybrid Synergy Drive system.
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On 01-May-18 4:49 PM, Steve H wrote:

Toyota's PSD works like a differential.
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On 01/05/2018 16:49, Steve H wrote:

??. the original problem with diesels was that they produced so much low-down torque that no auto box of the era could cope.
Auto diesel cars were very rare 20 years ago.
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Vauxhall sold a Victor with a two speed auto in the 50s or 60s. Maybe just about OK on a US V-8, but not on a 1.5 litre UK car. As the saying goes, couldn't get out of its own way...
Rolls actually made a car with only one forward gear and a torque converter. Early last century. Don't think it was a success. ;-)
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On 01-May-18 5:06 PM, Dave Plowman (News) wrote:

Possibly what gave autos a bad name.
but it could be towed as it had a 2nd pump on the output shaft.
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On 30/04/18 14:49, Dave Plowman (News) wrote:

I'm sure I remember you doubting this sort of box a few years ago :-)
My DSG (the second one I've had) is great. Rarely in the wrong gear, and as fast and economical as a manual.
On the other hand, I had the misfortune of driving a Toyota MMT (automated single-clutch manual) recently and it was awful beyond belief.
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Based on experience of earlier ones, yes. They seemed to major on 'sporty' (ie snatchy) gear changes as a virtue. And over enthusiastic use of low gears when not needed.

It's obviously far more difficult to get a smooth change with a single clutch type.
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On 01/05/2018 00:46, Dave Plowman (News) wrote:

This was vile. Obviously, with a 3-cyl 1-litre engine it's never going to be a thrill, but at low speed it was jerky, and felt like it would stall at any moment. The change from 1-2 was so slow that on any sort of incline it lost momentum and got bogged down in second.
It had paddle shifters, and they actually got used, to override the poor choices the ECU made.
If it was anyone's first experience of an autobox it'd be enough to put them off for life. To be fair, I'm told that VW's version (ASG) in the up! is just as bad. I just think it's a flawed concept, built for low cost, economical production, and low emissions (on paper, at least).
I really think that unless you can justify the cost/weight/complexity of a DCT then you'd be better sticking with the inherent losses of a TC/epicyclic auto.
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On Mon, 30 Apr 2018 14:49:46 +0100, Dave Plowman (News) wrote:

Sounds like a potential bank-breaker if it goes wrong, Dave. Nowadays I'm avoiding anything overly complex and going back to full-on retro. I've learned the hard way!
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Most autos tend to have a pretty good life. They're much more difficult to abuse than a manual.

This is my everyday car. One old one is enough for me. ;-)
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On Tue, 01 May 2018 23:54:13 +0100, Dave Plowman (News) wrote:

IME complexity and reliability run in inverse proportion to one another. You've got one hell of a complex box there by the sound of it.
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Cursitor Doom wrote:
[snip]

My experience of running cars since 1970 is that the more modern cars are less reliable in terms of sophisticated features that fail and can't be repaired by your average garage, or the main dealer - at least not without significant cost.
The early cars would rust away, or their gearbox bearings would fail, or suffer cracked cylinder heads. Since they were already old (10 years was old in those days) and I was broke I would generally repair what I could myself - though the rust would normally be terminal. But the failures seemed functionally significant - clearly the car would have to be repaired or thrown away.
More recently (on cars about 10 years old) I have seen failures in more sophisticated sysems:
1. Aircon failure because of slow leaks in the system, and because of an intermittent fault in the wiring from a temperature sensor so the system would shut down at random.
2. Airbag sensor failure in driver's door, necessitating complete dismantling of door to repair. Repair cost about £400 for a car worth under £3,000 at the time.
3. Air leak in diesel fuel system, such that if car war parked nose-up on a sloping drive for more than two days the fuel line between tank and injector pump would empty, necessitating cranking continuously for several minutes to get it started. Local garage was never able to find the problem despite replacing much of the pipework and the filter housing. I traded it in sometime July 2015 for a few hundred quid and I still see it being driven about by a taxi company in Diss, Norfolk. I guess they park it on level ground, and run it very frequently.
The first two of these faults did not prevent the car from being driven, though number 2 was an MOT failure as discussed in previous posts.
So "complexity and reliability run in inverse proportion to one another" - I agree.
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On Wed, 02 May 2018 08:50:03 +0100, Graham J wrote:

Yup, a significant cost in proportion to the value of the car, making what were previously considered minor faults into terminal issues effectively requiring the car being written-off. BTW, your personal experience chimes in precisely the same as mine.
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Tends to be because most garages don't have people trained in electrics/electronics. Or even with much in the way of training at all.
Quite understandable as the customer is just used to paying whatever they ask for.
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