Launching car on snow – XDS+ braking rear wheels?

Car: 2016 Golf R, 6-speed manual, stock

Launching the car on snow with the ESC / TC turned off (holding the button down for 3 sec), I notice that the rear wheel(s) are slowed down momentarily. I don’t think the traction control is intervening (since it’s turned off). I guess this is due to the XDS+ applying the brake on one side forcing the torque to the opposite wheel via the open diff? Poor man’s torque vectoring? Weird...

https://www.youtube.com/watch?v=ZxkQGqIE31k

https://www.youtube.com/watch?v=5U9fzAtAvhE

https://www.youtube.com/watch?v=jK13TQpR0E0

I can not see video unless others can.

^ How do I embed videos? It works on other forums...

Edit: Changed to URL, cannot embed...

Ferrari said:

^ How do I embed videos? It works on other forums...

Edit: Changed to URL, cannot embed...

Click to expand...

Wow! Cool video showing the Haldex gen5 doing what it should do.
Also XDS+ seems to work great...

Thanks rafycotto! u2b was what I was missing...

XDS+ only works on (quicker driven) bends, not when launching.
It's the common EDS what's braking the slipping wheel here.

What tires are you running?

What's EDS? Electronic Differential System? Isn't that part of the XDS+?

Nokian Hakka R2

Actually any feature is part of the entire system today, and anything is working
hand in hand, so take this with a grain of salt.

This is quite old stuff (ABS almost 40 years, ESC about 20 years) found on any
current passenger car:

ABS - anti-lock brake
EDS - electronic(ally imitated limited slip) differential - brakes a slipping wheel (hardly until it tends to lock)
ASR - anti-slip control - reduces engine torque when driven wheel slip
ESC/ESP - stability control/programme - compensates understeer and oversteer

Contrarily this is quite 'new' (as Volkswagen invented XDS on the Mk.VI GTI) and
still kind of 'exclusive' (to the Golf/GTI/R and some few competitors like BMW):

XDS - brakes the inner front wheel smoothly on quick bends before slip/understeer occurs (Mk.6 GTI & Mk.7 R & any Euro Mk.7 Golf)
XDS+ - smoothly brakes both inner wheels on quick bends before slip/understeer occurs (Mk.7 GTI)

. . . helping both turn in + traction and reduce understeer. This is mainly to enhance
performance on spirited driving, not that much a safety thing as is ESC, while EDS is
mainly intended to climb steep hills covered with snow.

Let me add, EDS does neither substitute some feel in your right foot nor a real LSD.
With EDS working the slipping wheel is never in the optimum state (of say 10 to 30 %
slip), but permanently swinging between almost locking and desperately spinning. This
way the resulting traction is far from optimum.

breaking badly, thanks! Makes sense. So EDL and XDS are technically different, one reactively brakes a faster rotating wheel in a straight line, and the other preemptively (predictively?) brakes the inner wheel in corners.

From VW's technical glossary:

Electronic Differential Lock (EDL)
The electronic differential lock permits smooth, comfortable starts on split-friction road surfaces with differing levels of grip. If one wheel starts to spin, the electronic differential lock will brake the wheel as necessary, directing power to the wheel with better grip in the process. The electronic differential lock reduces tyre wear and operates at speeds of up to around 40 km/h (4MOTION: up to about 80 km/h). As a software function, it forms part of the electronic stability control (ESC) and traction control (ASR).

Electronic Differential Lock (XDS)
The XDS electronic differential lock is an extension of the familiar EDL function. However, XDS responds not to loss of traction but to the unloading of the front wheel on the inside of the corner when cornering fast. XDS applies pressure from the ESC hydraulics to the inside wheel to prevent it from spinning. This improves traction and reduces the tendency to understeer. The level of pressure applied ranges from approximately 5 to 15 bar. The impression when driving is similar to that of a limited-slip differential in toned-down form. The precise, one-sided build-up of brake pressure makes cornering even sportier, quicker and more accurate.

Actually, I recall that XDS acts only on front and XDS+ on both front and rear (R only)

The Mk.7 GTI (at very least Euro spec) is definitely equipped with XDS+
while I don't remember Volkswagen saying the same about the R. They
just say the R has XDS, but feel free to provide a link proving me wrong.
I'd suggest to try this site:

https://www.volkswagen-media-servic...le-Golf-Golf-R/search/81188_81260_81432-81492

There's little to no info about this, at least no clear statement about it. Maybe the FL got XDS+ ? Or maybe just Mk7 vs Mk6.
But I'm 100% sure the R had it already (pre-FL)

https://www.topgear.com/car-reviews/volkswagen/golfgolf-sv/20-tsi-r-5dr-dsg/first-drive

Not wanting to be anal at all, but Top Gear is not a reliable source.
To begin with they say that XDS is what you find on the GTI which
is definitely wrong.
Journalists quite often don't even know what they're talking about.

Don't get me wrong though, as I'm not saying the R doesn't come
with XDS+, I'm just not convinced since there's a lack of information.
That said, does it even matter if the R does brake both inner wheels
or just one? It's a damn competent car anyway.

Does turning esc to sport or all the way off, affect the xds on the R in any way?


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