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How the VW Golf GTI Performance Pack (PP) “Front Differential Lock” (VAQ) works.

oddspyke

Go Kart Newbie
Location
Nazareth, PA
So what I'm getting is XDS would have to be almost off to get any benefit of the FDL? correct?
Definitely not. Although it could allow the VAQ to do more with less intervention, even just putting the car in TC off / ESC sport setting gets huge performance gains as evidenced by many on track reviews and tests. VAQ equipped cars routinely shave several seconds off of lap times as compared to the base model. I'd also be wary of fully defeating the XDS as golfdave rightly points out, it operates as an integrated system and we don't actually know how it will respond if you take part of it away.
 

golfdave

Drag Racing Champion
Location
Scotland (U.K.)
Ride
MK7 Golf GT Estate
So what I'm getting is XDS would have to be almost off to get any benefit of the FDL? correct?
Yes & no...

what the problem is the transition between the XDS intervening & the FDL taking over...

The XDS will want to intervene first as its a safety system & is higher priority compared to the FDL unit...so the car will try to sort the lack of grip out with XDS/ABS etc first..

However in certain situations you want the FDL to be active & sort out the grip & the XDS to turn off.....

So you have to "back off" (set to weak) the XDS to allow the FDL to operate....in these conditions..


This is only for certain conditions & not "all the time"..way to many variables to list here...
 

alper

Ready to race!
I have quoted directly your first post as you have selectively forgotten what you wrote....& put in bold some pertinent sentences...

I'll leave it to the mods....but please leave the thread open as you can see that quite a few forum members find it usefull...alper being the only one who does not so far.....out of over 900 views
Thanks, it's quite obvious how I liked the technical aspect then (please for once more don't claim things about me that I never said like that I don't find the thread useful :confused: ) and to that I added that some hands-on experience could have given you a different view as theory and practice are not cancelling but instead complimenting each other.

In particular, regarding the "unpredictability" comment in the final paragraph. That was an arbitrary conclusion based on the fact the system could not be simulated accurately during a Bachelor's thesis which could be down to tenths of different factors. Especially, since If one thing could be praised the most about the VAQ is the exact opposite, how smooth and predictable it is and that it never catches the driver off-guard with the way it operates ;) Anyone in research and R&D could testify it's not unusual to have several failures in an attempt to study something only to come back with an improved model/setup and tackle it successfully in the end. Nothing strange there and after all the system has already been tested and proven itself in millions of miles on VAQ equipped cars without any mentions of such quirks and hiccups whatsoever, unless I'm unaware of them.

Other than that it's all good and we'll keep on seeing more of those systems on our cars in the coming years, for the better. Yes, a bit of extra maintenance (hardly an issue for anyone caring for his own car) and as with everything including electronics more things to go wrong (although there are far more issues with turbos, clutches, suspension that have been reported than with the diff itself...) but I see as an overall more complete and integrated locking differential solution, one that can act proactively and promote both safety and fun at the same time. Almost a win-win in my eyes.
 

ucfquattroguy

Ready to race!
Location
Florida USA
Just to keep this a bit more on-track (pun not intended)...I think the electronically controlled slip limitation is just scratching the surface for what's possible at the moment. Another thing to keep in mind: Any of the "annoyances" of the VAG applications of the FDL is 100% down to the software VAG loaded to the control unit. Despite what we (the small minority of enthusiasts) *want* it to do, let's not forget that the behavior is completely as what the factory wanted (the reasons don't matter for this discussion). This type of system has the potential to completely blow a mechanical diff out of the water given the software is written appropriately. Don't get hung up on the fact that ABS sensors and such can be viewed as 'safety systems'. Focus more on the fact that the control modules are using these existing sensors to take in a TON of data in real-time to arrive at a decision as to what to do and when to do it.

Not VAG application related, but there is a factory option on one of the Chevy Camaros at the moment that is an electronically controlled LSD. GM sets some money aside for an in-house team of enthusiasts to run one of these around the country at SCCA Autocross events in a class that allows diffs, springs, pimpy shocks, etc. One of the tweaks they did was a complete re-write of the diff software to be optimized for that type of racing (they are factory guys...so of course they have the ability to do this). A few top drivers not on the team have had the opportunity to drive that car and their first take-away was just how good the diff was and how well the car put power down. It would apply a bit of lock on decel to keep stable under braking. As soon as you turned in, the lock reduced so the car would roll freely through an apex, then would gradually increase lock as throttle input increased and steering input reduced. Quite fascinating really.
 

alper

Ready to race!
Just to keep this a bit more on-track (pun not intended)...I think the electronically controlled slip limitation is just scratching the surface for what's possible at the moment. Another thing to keep in mind: Any of the "annoyances" of the VAG applications of the FDL is 100% down to the software VAG loaded to the control unit. Despite what we (the small minority of enthusiasts) *want* it to do, let's not forget that the behavior is completely as what the factory wanted (the reasons don't matter for this discussion). This type of system has the potential to completely blow a mechanical diff out of the water given the software is written appropriately. Don't get hung up on the fact that ABS sensors and such can be viewed as 'safety systems'. Focus more on the fact that the control modules are using these existing sensors to take in a TON of data in real-time to arrive at a decision as to what to do and when to do it.

Not VAG application related, but there is a factory option on one of the Chevy Camaros at the moment that is an electronically controlled LSD. GM sets some money aside for an in-house team of enthusiasts to run one of these around the country at SCCA Autocross events in a class that allows diffs, springs, pimpy shocks, etc. One of the tweaks they did was a complete re-write of the diff software to be optimized for that type of racing (they are factory guys...so of course they have the ability to do this). A few top drivers not on the team have had the opportunity to drive that car and their first take-away was just how good the diff was and how well the car put power down. It would apply a bit of lock on decel to keep stable under braking. As soon as you turned in, the lock reduced so the car would roll freely through an apex, then would gradually increase lock as throttle input increased and steering input reduced. Quite fascinating really.
Thumbs up man. Electronically controlled diffs open up a world of possibilities due to the nature of the system working under a controller processing all that input data and calculating best possible reaction at all times. I believe I'd read somewhere they are already employed by some racing teams because they offer so much adjustability that a traditional mechanical can't.
There are certainly not used as a safety system there so it must be purely down to the level of performance they can hit, with the right software of-course. It's more than certain we'll see the VAQ ever-improving with every new gen similarly to how the AWD Haldex has since it began.
 

heiney9

Go Kart Champion
Location
Illinois
I have to say after the 4 inches of snow last night, and the crappy job they did clearing the streets this morning, the LSD in the P/P actually assists when turning on snowy roads. Turn off traction control via the switch and go into manual mode (I have DSG). I went around snow/slush filled corners on those horrible Pirelli P7 Cinturato A/S tires (I don't think the P7's are as bad as most here) with more momentum and confidence than in any other VW I've owned.

I hadn't really had a chance to assess if the LSD would make a difference in snow, but all early indications it seems to. You can't drive crazy into a turn in the snow/slush and expect it to save you, but you can carry a bit more speed and feel more confident the front isn't going to plow and drive straight through the corner.

It certainly seems to help if the ASR is off via the button and you are in manual mode of the DSG where you have more control over gear selection and throttle input.

Impressed.
 

golfdave

Drag Racing Champion
Location
Scotland (U.K.)
Ride
MK7 Golf GT Estate
Just to keep this a bit more on-track (pun not intended)...I think the electronically controlled slip limitation is just scratching the surface for what's possible at the moment. Another thing to keep in mind: Any of the "annoyances" of the VAG applications of the FDL is 100% down to the software VAG loaded to the control unit. Despite what we (the small minority of enthusiasts) *want* it to do, let's not forget that the behavior is completely as what the factory wanted (the reasons don't matter for this discussion). This type of system has the potential to completely blow a mechanical diff out of the water given the software is written appropriately. Don't get hung up on the fact that ABS sensors and such can be viewed as 'safety systems'. Focus more on the fact that the control modules are using these existing sensors to take in a TON of data in real-time to arrive at a decision as to what to do and when to do it.
Well put...:cool:

Like I stated :- "The FDL can talk to the other electrical systems as previously mentioned, & thus can react way quicker & in a finer & more precise way than a mechanical LSD can only dream of."


The safety side most people do not fully grasp...because the FDL unit takes the data from the ABS sensors as it does not have its own, its classed as a secondary unit....the primary unit is the ABS system.so this is easy to sell in a litigious society,...

.... compared to an LSD which operates on its own & only reacting to torque transfer % imbalance across the axle/wheels....therefore no feedback to other safety systems, as no electronics..other than the existing "out of the loop" ABS sensors which will register that the wheels are not slipping, but the Yaw, long/lat sensors will notice increased G-forces....so everything will be "fine" until you really push it & the tyres break traction suddenly & therefore too late (possible) for the safety systems to intervene..

Integrating the FDL unit etc into the ABS systems etc, etc, make the safety net of the car a "whole"...which is why its done also...

However considering we on this forum & others are setting the various systems to "weak" & less nanny, what I would be concerned with is "If" big IF" these settings in say the MK8 were locked in & thus VCDS etc could not alter them. Much like the FAZIT component protection which was introduced in the MK7.....ie due to insurance etc you ain't allowed to alter the car from factory on the "safety" systems.....

Not paranoid, just pragmatic...they let you play on their terms....

BUT "IF" they improve the programming & really do it well then their should be no problems...much like some ABS systems are now allowing the wheels to lock & form a "chock" in front of the wheel when in certain modes...as in certain cases ABS is useless & increases your stopping distance...

However one point I found interesting was that the TCR cars were introduced in DSG/FDL only...then they bought in the Sadev Sequential gearbox with Mechanical LSD upgrade & a new car build the following year......& not put the FDL on the sequential gearbox which they could have done. So you have two completely different cars on the same track, totally "analogue" & totally "digital"...with a 40kg weight difference between them..(2017)
 

golfdave

Drag Racing Champion
Location
Scotland (U.K.)
Ride
MK7 Golf GT Estate
I have to say after the 4 inches of snow last night, and the crappy job they did clearing the streets this morning, the LSD in the P/P actually assists when turning on snowy roads. Turn off traction control via the switch and go into manual mode (I have DSG). I went around snow/slush filled corners on those horrible Pirelli P7 Cinturato A/S tires (I don't think the P7's are as bad as most here) with more momentum and confidence than in any other VW I've owned.

I hadn't really had a chance to assess if the LSD would make a difference in snow, but all early indications it seems to. You can't drive crazy into a turn in the snow/slush and expect it to save you, but you can carry a bit more speed and feel more confident the front isn't going to plow and drive straight through the corner.

It certainly seems to help if the ASR is off via the button and you are in manual mode of the DSG where you have more control over gear selection and throttle input.

Impressed.
Bold...this is the problem, the programming the Factory set ATM is not for all people or all situations...so long as we can alter the settings via a button or VCDS then fine..in a manual car ASR off would be fine, & a manual car with an LSD would be ok...but you had to effectively turn the car into a "manual" control car to get it work how you wanted & better in that situation..


Your observations again prove that the safety systems intervene first & that the FDL is secondary..& the only way to get to use the FDL unit in certain conditions & to stop the FDL unit fighting the XDS etc is to turn off, or turn down the XDS etc...
 

heiney9

Go Kart Champion
Location
Illinois
The factory setting will NEVER be for all persons in all situation in any car, so that's a given and assumed. There is no PROBLEM as you state.

Manuals by their very nature allow more control (input) in the snow. I always drive in manual in the snow, it only makes sense to me since for the past 35 years I've drive standard transmission cars.

I am complementing the way the car handles in snow because of the LSD. Somehow because of your bias against it, you're trying to say something derogatory about the system and it's shortcomings.

I am relaying my experiences and impressions in the "real" world driving, not trying to analyze it's shortcomings on paper.
 

golfdave

Drag Racing Champion
Location
Scotland (U.K.)
Ride
MK7 Golf GT Estate
The factory setting will NEVER be for all persons in all situation in any car, so that's a given and assumed. Agree

Manuals by their very nature allow more control (input) in the snow. I always drive in manual in the snow, it only makes sense to me since for the past 35 years I've drive standard transmission cars. Agree

I am complementing the way the car handles in snow because of the LSD. Somehow because of your bias against it, you're trying to say something derogatory about the system and it's shortcomings. Stated many times it can react way quicker than a mechanic LSD can only dream of..& as you found out when the settings are right it will perform very well.

I am relaying my experiences and impressions in the "real" world driving, not trying to analyze it's shortcomings on paper Unfortunately what sometimes happens is some people do not know what systems is activating, or why the FDL acts or not in certain situations, all I was trying to do is clarify its "design parameters" & limitations. Unfortunately some people don't like this. Yes it has its flaws, but so did the Haldex AWD unit in the MK4 R32 which was laggy as hell....Did it make a bad car, NO...flawed, yes, but very good when you knew how to get the best out of the AWD unit because you knew how it worked down to the last detail.(been there done that), buy putting out loads of correct good/bad info people can now see exactly what its limitations are & use it more effectively, & hopefully get more out of it....
Answers in bold
 

ucfquattroguy

Ready to race!
Location
Florida USA
RE: the TCR cars... Here in the US, the TCR class is actually being phased into the Continental Tire Challenge Series (IMSA Feeder/support series). The rule book mandated that the VWs are the versions with DSG and VAQ. Pretty neat.
 

golfdave

Drag Racing Champion
Location
Scotland (U.K.)
Ride
MK7 Golf GT Estate
RE: the TCR cars... Here in the US, the TCR class is actually being phased into the Continental Tire Challenge Series (IMSA Feeder/support series). The rule book mandated that the VWs are the versions with DSG and VAQ. Pretty neat.
UK has the 24Hr TC series & both (Sadev & DSG) are allowed...& the same in the TCR series later in the year..

Basically we are now under the TCR international series...regs state:-

"Mass production gearbox coming from the production model or from another car of the same group may be used (Certification). In the latter case a gear box adapter to the engine and gearbox brackets may be used. (Certification"

One racing sequential gearbox with one set of ratios may be certified under following conditions:

A 2nd racing sequential gearbox can be certified at any time as option VO using similar technical parameters

Any mass production limited slip differential may be used in mass production gearbox with production parameters but the settings cannot be modified during driving. (Certification)

The mass production differential fitted in the mass production gearbox may be replaced by a catalogue mechanical limited slip differential inside the drive unit housing (Certification). ""

which is why the Sadev sequential with mechanical LSD is offered as a new build or upgrade...plus its 40kg lighter than the DSG/FDL units...

which helps in a race car...:cool:
 

Wrath And Tears

Go Kart Champion
Location
Azusa, CA
Hey golfdave, I might have missed it, but have you come across anything that says what exactly changing the VAQ from normal to traction mode does to the VAQ unit? This is different from changing the FDL to sport mode, and is how the CSS (and Seat Cupra 280) comes stock.

From personal experience it totally changes how and when the VAQ kicks in, but it would be cool to know what exactly happens.
 

ucfquattroguy

Ready to race!
Location
Florida USA
I'm sure you'd have to get somebody at VAG or BW who was involved in the module programming to give you anything meaningful. My guess is that it changes some of the thresholds the programming looks for before taking any action. it may rely on the XDS a bit less in the increased traction modes before the FDL's control programming sees a need to do anything. Whereas the normal adaptation may try to let XDS+ handle things as much as possible before needing to initiate lockup.
 

Trancebolt

Ready to race!
Location
California
I just want to point out that there are many cars out there with only a brake vectoring only and are very competent. It comes down to feel, for me.

Sent from my SM-G930T using Tapatalk
 

golfdave

Drag Racing Champion
Location
Scotland (U.K.)
Ride
MK7 Golf GT Estate
Hey golfdave, I might have missed it, but have you come across anything that says what exactly changing the VAQ from normal to traction mode does to the VAQ unit? This is different from changing the FDL to sport mode, and is how the CSS (and Seat Cupra 280) comes stock.

From personal experience it totally changes how and when the VAQ kicks in, but it would be cool to know what exactly happens.
There is virtually nothing not even a graph ...on the % lock of the unit at say X wheel speed & % torque input & torque % split etc....in various VW stuff ...however there is stuff from BW , but I'll have to screen grab & post up & its very technical....

give me some time..

EDIT:-

Info I thought would show what you want doesn't...& the info it does show is 360 res as its from a webinar...

bugger...
 
Last edited:

rafal83

New member
Location
Poland
Hi, great post and piece of information! I'm coming from Seat community in Europe owing stage 2 Leon Cupra which uses the same system as Golf PP. I tried recently to understand better VAQ due to the problem i have with torque steer. During hard acceleration my left wheel gets too much torque, spinning faster than right. Even at high speed over 100km/h when (full load) I checked with VCDS - left wheel spins faster, then ESP light on the dash tries to (perhaps) brake it and so on....at the end it pulls to the right. In my simple understanding the VAQ should efficiently manage torque between both wheels, but sounds is not like this. Despite some mechanical suspension failure what can cause such an effect? Are there any adaptations in ESP that should be done? I did many times basic settings in module 32, but it didn’t change. There are no errors, nothing. Or 500NM of torque combined with 400HP is too much for this car.
 

Wrath And Tears

Go Kart Champion
Location
Azusa, CA
There is virtually nothing not even a graph ...on the % lock of the unit at say X wheel speed & % torque input & torque % split etc....in various VW stuff ...however there is stuff from BW , but I'll have to screen grab & post up & its very technical....

give me some time..

EDIT:-

Info I thought would show what you want doesn't...& the info it does show is 360 res as its from a webinar...

bugger...
Ah balls, thanks for looking though. I'll ask next time I'm at a VW/Audi class. Have a few coming up this year.
 

golfdave

Drag Racing Champion
Location
Scotland (U.K.)
Ride
MK7 Golf GT Estate
Ah balls, thanks for looking though. I'll ask next time I'm at a VW/Audi class. Have a few coming up this year.
No problems..the info was a BW webinar video must of it is about the grip & steering angles input & forces compared to 2wd with out & the AWD...& even that is powerpoint rubbish & bad graphs......

But nothing on the parameters eg how much it tells the FDL unit to lock up & if early or does it lock up quicker & by how much in sport mode etc..

In fact the only info I have found on that is the maps on the FDL unit in the TRC race car which I mention in the write up...
 

golfdave

Drag Racing Champion
Location
Scotland (U.K.)
Ride
MK7 Golf GT Estate
Hi, great post and piece of information! I'm coming from Seat community in Europe owing stage 2 Leon Cupra which uses the same system as Golf PP. I tried recently to understand better VAQ due to the problem i have with torque steer. During hard acceleration my left wheel gets too much torque, spinning faster than right. Even at high speed over 100km/h when (full load) I checked with VCDS - left wheel spins faster, then ESP light on the dash tries to (perhaps) brake it and so on....at the end it pulls to the right. In my simple understanding the VAQ should efficiently manage torque between both wheels, but sounds is not like this. Despite some mechanical suspension failure what can cause such an effect? Are there any adaptations in ESP that should be done? I did many times basic settings in module 32, but it didn’t change. There are no errors, nothing. Or 500NM of torque combined with 400HP is too much for this car.
that power is above what the car can cope with with out any wheelspin...

Usually you should try the best tyres Conit sport contacts or PS4,s...then suspension etc ..

You can reduce the intervention of the XDS (ESP light) by adjust a setting in the ABS unit (labelled expanded difflock) to "weak"...this will allow the VAQ unit to do its job better.

when you spin the wheels..the left (when sitting in the car) wheel will spin faster then the right one as the VAQ unit is on the right side of the gearbox....& the left drive shaft is lighter shaft is therefore spins easy..the right drive shaft goes through the VAQ unit & has the extra weight/mass of the clutch's to spin therefore slower... before the ABS sensors tell the VAQ to operate..
 
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