The new Haldex 5 in the Golf VII - wonder if it will feature in facelift Yeti?

[900000]

http://www.autocar.co.uk/car-review/volkswagen/golf/first-drives/volkswagen-golf-4motion-20-tdi-first-drive-review

Some interesting updates there like a move away from a hydraulic pump to an electric one. Also of note is that the Golf's towing rating goes up by 400kg over the 2WD to just 100kg shy of the Yeti's 2000kg. Which is similar to the Yeti's increase when you go from two to four wheel drive.

[Norry]

http://www.autocar.c...st-drive-review

Some interesting updates there like a move away from a hydraulic pump to an electric one.

The Haldex IV has the electric pump already, the haldex site descriptions of the IV and V are identical, I would like to know what the improvements are.

Edited 1 February, 2013 by Norry

[900000]

Ha!! Shows you how much Autocar knows then! (and I! )

[Yety]

The Haldex IV has the electric pump already, the haldex site descriptions of the IV and V are identical, I would like to know what the improvements are.

If you read the article, it says the accumulator has been done away with, saving 1.4 Kg - so it can't be identical.

If this is true or not is debateable as their wording of a "hydraulically driven pump" is a little strange, surely the pump is electrically driven.

Perhaps they mean the new system electrically pumps fluid directly, controlled electronically?

Who knows exactly?

[briskycat]

I guess by "an electrically operated device" they imply an electric actuator of some sort, not a pump + a hydraulic actuator as in 4th gen Haldex.

[r999]

This should make it all a bit clearer: http://forums.swedes...rformance/page2

By doing away with the pressure accumulator in favour of a cheaper centrifugal valve, the Haldex 5 apparently reacts more slowly than the 4, but opinion is divided on whether this will spoil its performance.

There's a video lower down the page of two Volvos towing each other that's meant to show the new one is no worse, at least, than the old.

Edited 2 February, 2013 by r999

[briskycat]

There is a video on the official BorgWarner site that explains how V generation Haldex coupling works: http://www.borgwarner.com/en/Haldex-AWD/products/Pages/Haldex-Gen5.aspx

The pump is still there, but it is combined with a pressure-regulating device, making the overall design simpler compared to IV gen.

[loftypeak2]

B****r; does that mean that I am going to have to change my (not yet delivered) Yeti no.2 when that reaches 2 yrs old?

[Llanigraham]

No, why?

[r999]

You might want to hang on the old one.

One of the main complaints about early Haldex systems was their slow reaction time. Now that the Americans have bought Haldex from the Swedes, they have set about doing what American automotive engineers always do: finding a way to make it more cheaply and hoping that not too many people will notice that it doesn't work as well.

The fact that the Haldex 5 reacts a few hundred milliseconds more slowly than the 4 is probably going to make no difference at all in mud or snow. However, the concern might be that slower reaction times could spoil a car's neutral handling on tarmac. One some Haldex-equipped cars (depending on the programming of the electronics), the torque split to the rear wheels drops to around 5% or 10% only when cruising and travelling in a straight line. At other times, such as a slalom manouevre or energetic cornering, the Haldex is adjusting torque split to counteract understeer and oversteer: in other words, to give the car excellent handling on demanding roads, even though no loss of grip is involved at all. It is said that this is what enabled the Saab 9-3 Turbo-X to beat loads of very high-performance cars in the slalom test.

I wonder how much of the 4WD Yeti's good handling on tarmac would be compromised by a slower Haldex?

[Yeti_Man]

Saab's XWD is actually what we have on the Yeti, generation 4 haldex, just that Saab got it first. That's my understanding anyway. This system is far far superior to previous generation 2 haldex equipped vehicles that I've driven and owned ie no slip needed for activation and neutral handling, no noticeable passing of the power fore and aft. :-)

[Norry]

There is a video on the official BorgWarner site that explains how V generation Haldex coupling works: http://www.borgwarne...aldex-Gen5.aspx

The pump is still there, but it is combined with a pressure-regulating device, making the overall design simpler compared to IV gen.

But, as I wrote before, that description is the same as they have for the Mark IV.

It does seem that the newer system is slower to operate the non spinning wheels than the old one which is supposed to detect the wheel spin within 1/7 of a revolution.

Edited 3 February, 2013 by Norry

[briskycat]

But, as I wrote before, that description is the same as they have for the Mark IV.

Not exactly the same. Note "The pump sets the pressure to the piston which in turn compresses the disc package" vs "The control valve sets the pressure to the piston which in turn compresses the disc package".

In the Mk. IV Haldex there was a separate pressure regulator, controlled by a separate electrical actuator, which was fast. At least that is what is shown in various diagrams. In the Haldex 5 there is a centrifugal pressure regulator mounted directly on the shaft of the pump. The only way to control it is by changing the speed of the pump (the higher the speed, the higher the pressure). Which doesn't seem to be as fast...

[r999]

In the Mk. IV Haldex there was a separate pressure regulator, controlled by a separate electrical actuator, which was fast.

The reason it was fast was because it had a pressure accumulator. That meant full pressure was already generated and available in the accumulator, waiting to be released instantly.

[briskycat]

Well, an accumulator stores not pure pressure, but energy that can be released later. That energy can never be released instantaneously. The rate at which it can be released (the power) depends, particularly, on the type of valve used. If you have a equally powerful pump, you can do without the accumulator.

I think the reason why they used a pressure accumulator in Haldex 4 was energy efficiency of the whole unit or something like that.

Edited 3 February, 2013 by briskycat

[r999]

Well, an accumulator stores not pure pressure, but energy that can be released later. That energy can never be released instantaneously. The rate at which it can be released (the power) depends, particularly, on the type of valve used. If you have a equally powerful pump, you can do without an accumulator.

I think the reason why they used a pressure accumulator in Haldex 4 was energy efficiency of the whole unit or something like that.

That leaves you to explain why the Haldex 5 without the pressure accumulator is known to have a considerably slower response time.

Edited 3 February, 2013 by r999

[briskycat]

Because it takes time to spin up the pump for the centrifugal regulator to kick in

[Yeti_Man]

That leaves you to explain why the Haldex 5 without the pressure accumulator is known to have a considerably slower response time.

I must be missing the obvious here but what proof do you have that its slower?! The driving experience from the journo's point of view with the new Golf is that "In gentle part-load running, the Haldex 5 system is set up to predominantly drive the front wheels. But when pushed hard it is capable of sending up to 100 per cent of the engine's power to the rear wheels. The new set-up, with its electronically controlled pump in place of the hydraulically operated arrangement, is noticeably more responsive than the old system, providing great purchase in corners and an ability to lay the latest version of Volkswagen's 2.0-litre four-cylinder TDI's prodigious low-end torque to the road without fuss."

[Llanigraham]

That leaves you to explain why the Haldex 5 without the pressure accumulator is known to have a considerably slower response time.

Define considerably in this context?

[Norry]

I must be missing the obvious here but what proof do you have that its slower?!

The new set-up, with its electronically controlled pump in place of the hydraulically operated arrangement, is noticeably more responsive than the old system, providing great purchase in corners and an ability to lay the latest version of Volkswagen's 2.0-litre four-cylinder TDI's prodigious low-end torque to the road without fuss."

The point is that description is not correct - the old system, the Haldex IV, already has the electric pump - it was the Haldex III that had the mechanical pump driven off the transmission. Their really ain't no such thing as a hydraulically driven pump on a car!

[r999]

Because it takes time to spin up the pump for the centrifugal regulator to kick in

In other words, the reason for the slower response is they are using a pump and centrifugal regulator instead of an accumulator, which I said in the first place, you denied, and you now admit. Sheesh...

Edited 3 February, 2013 by r999

[r999]

I must be missing the obvious here but what proof do you have that its slower?!

I refer you to this thread - 38 pages of it - where unhappy Swedes complain a lot about the Haldex 5. http://www.jagrullar...&st=0&sk=t&sd=a These people have been trying to get their cars 'fixed' or their money back. Not being a Swede nor owning a car with Haldex 5, I can't vouch for this personally, but I rather doubt they are just making it all up.

Define considerably in this context?

'Awesomely lazy' is just one of the terms used to compare the Haldex 5 with the 4.

Edited 3 February, 2013 by r999

[Llanigraham]

Fine, but that is a meaningless statement.

Are we talking seconds or micro-seconds?

And can you tell me where that quote came from?

[Totally Square]

... driving experience from the journo's point of view with the new Golf is that " The new set-up, with its electronically controlled pump in place of the hydraulically operated arrangement, is noticeably more responsive than the old system, ."...

My guess is the journalist was regurgitating the VW PR briefing - he doesn't say he tried both systems back2back or even the older system at all. The Swede's reports are more believable, and if the 2014 Yeti gets new powertrains it may well get the (presumably cheaper, promise of more reliability?) Haldex5.

More interesting is VAG offering 1.6 as well as 2.0 TDi's, manual and DSG. I suspect a Yeti 1.6 4WD would provide a nicer Panda alternative for the chalet maid market in the Alps!

[ejstubbs]

The new set-up...is noticeably more responsive than the old system

My guess is the journalist was regurgitating the VW PR briefing - he doesn't say he tried both systems back2back or even the older system at all.

It's possible that the journo was comparing it to the Haldex used on the Golf VI 4-motion, which I'd suspect (anyone know?) is a previous version to the Haldex IV used on the Yeti.

I note that the Wikipedia article on Haldex says that: "version 4.0 Haldex made an effort to improve response time by eliminating the hydraulic pump". That is not dissimilar to the wording used in the Autocar article, which suggests to me that the journo has merely regurgitated some VW publicity material which compared the fifth-generation Haldex to versions prior to the Yeti's version 4.0. (And not regurgitated it very accurately either by the looks of it eg the "hydraulically operated pump" wording is, as Norry pointed out, nonsense.)

Edited 4 February, 2013 by ejstubbs