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Discussion Starter · #1 ·
The one question that I have about the new GTI that hasn't been adequately answered is whether or not the "XDS electronic differential" is a real, mechanical LSD that is electronically controlled (like the one in the Ferrari F430 or Nissan GT-R) or just a software program that brakes the inside wheel (like the Mini Cooper S JCW, BMW 135i, and Dodge SRT-4).
Given the expense and complexity of electronically controlled mechanical differentials, I'm left to believe that they are just braking the inside wheel (which, according to reviews of other cars with similar programs is ineffective to the point that it is useless).
Is there any concrete info on this yet?
 

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The MKV already has traction control (braking the inside wheel).
VW doesn't usually give marketing terms to "old" technology, so I'd expect this is something that's going to make a big difference in performance.
Plus, in the press release, it is the first thing that is mentioned about this new GTI. If it was some minor change, the DCC would have been the first thing mentioned, because that will be the first application of active dampers in a relatively cheap car.
My wild guess is that its a completely new type of LSD, probably designed to be cheap to manufacture, probably clutch based.
Actually, doing a bit of research... VAG's long-time LSD supplier, Haldex, has something that would make sense in this application:
http://www.haldex-xwd.com/
I bet you that the GTI will basically use the front half of that system. That makes sense, because the R could then easily use the entire system. If this conjecture pans out, we'll be looking forward to happy days.
-- The R currently only has a center differential; XWD has front, center, and rear differentials. This makes a big difference, because the R can currently only give 25% torque to each wheel symmetrically, or with the center clutch disengaged 50% torque to each of the front wheels. XWD can give any particular wheel 100% torque. Its a similar setup to what the EVO and GT-R have.
... here's hoping


Modified by curvedinfinity at 7:23 PM 9-27-2008


Modified by curvedinfinity at 7:31 PM 9-29-2008
 

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Re: (uhrgenau)

I am very curious as well and haven't found anything yet, either. German newspapers and magazines variously describe it as an electronically locking, sport, or transverse differential.
VW certainly made a big deal out of it in the press release, so it must be substantially different from the previous "electronic limited slip differential" = use of spinning wheel braking to send some (small) amount of torque to the wheel with traction. VW also stresses it dramatically improves handling - so it is not just to prevent torque steer and to get better 0-60 times (although it appears to do that, as well).
Remember that the MS3 must limit the torque to the wheels at low speeds to make it drivable, at all; it's superior power is only useful at higher speeds. We have long waited for a LSD or similar in the GTI --- to me at least it seemed more important than yet more power. However, knowing VW, they likely developed something a bit safer than a standard TorSen differential, which can be more than a handful for inexperienced drivers. Also, a smart system could ensure that even before the inside wheel slips, the outer one gets more torque (although it is spinning faster, and receives less in TorSen and clutch-type systems).
Of course, I want this in my GTD.
 

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Re: Is XDS a mechanical differential? (venom600)

While we are waiting for more details concerning the XDS, here is some information about the DCC electronically-controlled shock absorbers.
 

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Re: (dub*man)

Nothing.
As curvedinfinity already alluded to, my best guess also is that it is similar to the rear LSD in Saab's X-drive. That is, a transverse Haldex unit that gets activated under very slight differential rotation (i.e., what you have in simple cornering even without slip), but is under full electronic control. This basically surrounds the (open) front differential. It is not as big as the center Haldex unit, so it cannot fully lock the two sides, but it can transmit about 85% of max torque. At low speeds, individually applied brakes (EDL) can help a bit with that.

It would be pretty heavy, though, since unlike in the case of X-drive, it cannot make use of the existing components from the center Haldex unit (pumps, oil reservoirs and filters, housing, electronic control unit). So, it would be almost as heavy as a regular Haldex coupler (of course not the entire 200 lbs that include the long drive shaft and rear drive gear).
I assume that VW went this route because of fuel savings versus 4Motion (which is estimated at about 10% additional fuel consumption). When it comes down to it, anything even remotely similar to what I described above is still pretty expensive and heavy - if it were not for the fuel penalty, 4Motion Haldex would seem like the better solution, overall.



Modified by feels_road at 1:27 AM 11-11-2008
 

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go to northamericanmotoring a mini forum, moans about torque steer with LSD, it sure is not a peloquin or quaife, i love minis, i posted 275 TQ and NO torque steer, there was NO COMMENTS, mini uses a newer less effective unit, i researched and found it, cant remember the name, junk anyhow
 

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Re: (rodhotter)

Not sure I understand. I thought mini uses electronic brake distribution - which is what VW has had in their cars also, for years now (EDL).
This electronically-controlled LSD is thought to be an open diff with a surrounding clutch pack, which in turn is electronically controlled. EDL would come in to assist only if the one-sided torque load becomes higher than 85% of max, or so - something that typically only happens at low speeds on snow and ice.
 

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Re: (feels_road)

Again, it'd be great if we got some information about this. Especially if the Scirocco/GTI R20T is going to be FWD.
Isn't the GTI supposed to ship in Europe soon? Wouldn't they want this information out soon before the holiday buying season?
Jamie what's the deal here?
 

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Re: Is XDS a mechanical differential? (venom600)

Quote, originally posted by venom600 »
...or just a software program that brakes the inside wheel (like the Mini Cooper S JCW, BMW 135i, and Dodge SRT-4).

The 2004-2005 SRT-4s had a mechanical LSD in the transmission, the 2003s had an open differential.
 

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Re: Is XDS a mechanical differential? (Nick S)

I am seriously scratching my head here, what exactly is it you guys are looking for and where exactly did this IMHO misinformation come from?
The 5K (chassis code of the Golf 6) uses the 4th Haldex Generation, which was introduced in the VW Tiguan (5N). The 0AY haldex system in the Tiguan is slightly different, but the Golf shares its 0BR system with current Audi TT. So if you are looking for answers to your questions you might as well ask the TT guys or look it up in Audis documentation for it...
As far as I am aware this is a purely mechanical differential.
 

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Re: Is XDS a mechanical differential? (Theresias)

We are talking about the front differential of the FWD version, which in previous VWs has been open with EDL. With the MkVI GTI, VW has said that it will receive an electronically-controlled front limited slip differential - in pretty much all press releases about the car.
However, VW has not provided any details.
I see, you are more of a software guy...
<-- Einbecker Ur-Bock.
 

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Discussion Starter · #17 ·
Re: Is XDS a mechanical differential? (Theresias)

Quote, originally posted by Nick S »

The 2004-2005 SRT-4s had a mechanical LSD in the transmission, the 2003s had an open differential.

I was referring to the current SRT-4 based on the Dodge Caliber. It uses an open differential up front and brakes the inside wheel to get the effect of an LSD... only it sucks.
Quote, originally posted by Theresias »
I am seriously scratching my head here, what exactly is it you guys are looking for and where exactly did this IMHO misinformation come from?

You're talking about Haldex AWD. We're talking about the new "differential" VW is putting between the front wheels on the MKVI GTI.
 

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Re: Is XDS a mechanical differential? (venom600)

Quote, originally posted by venom600 »
I was referring to the current SRT-4 based on the Dodge Caliber. It uses an open differential up front and brakes the inside wheel to get the effect of an LSD... only it sucks.

Sorry, we both should've been more descriptive.
 

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Re: Is XDS a mechanical differential? (Nick S)

As I have no knowledged input to reply with my opinion is this. Its simplying an upgraded version of the old EDL. Sort of like how VW went from ASR to ESP.
 

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Quote »
...or just a software program that brakes the inside wheel (like the Mini Cooper S JCW, BMW 135i, and Dodge SRT-4).

I bet its a software system to brake the inside wheel during cornering to provide better turn-in response and a sharper feel. Def better than just an open diff, but a far cry from a Quaife/Peloquin style mechanical unit.
This is very different from ASR and EDL. EDL was designed to help traction at low speeds (upto 25-30 mph if I remember right) and usually disengages at higher speeds. XSD is supposed to work for fast driving and to improve cornering response so it should def work well.
Given that one of the goals with the MK6 was to reduce manufacturing cost, I doubt they would offer a full LSD. That would require a new transmission code and build up rather than just carrying over all the mechanicals from the MK5.
If someone has more factual information, I would love to be wrong
 
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