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DrFunkalupicus

Autocross Champion
Location
Topeka
Car(s)
2016 VW GTI S

Oversteermybagel

Go Kart Champion
Location
Boston
Car(s)
mk7 2017 GTi Sport
For starters The Seat Leon Cup Racer TCR Race cars were launched only with the DSG & the VAQ unit in 2015. Then from 2016 they offered the Sadev sequential gearbox with a mechanical LSD as an upgrade package or full new build. Quote from 2016 brochure:- “For the TCR series the car receives a new lighter & more individually adaptable transmission”. Basically, the racers wanted a sequential gearbox & a mechanical LSD. Thus, a lighter car (40kg less than DSG/VAQ for 2017) & more adjustment to suit driver & total predictability of the LSD, compared to the DSG/VAQ version. The DSG & VAQ launch in the TCR race cars was effectively a PR exercise to “prove” you could track the DSG/VAQ...the DSG & VAQ was proven too costly in terms of repairs & weight...

Secondly there are people on this forum who have removed the VAQ unit & fitted a Wavetrak.....so go ask them for their 100% direct experience of comparing the exact same car with VAQ & then with VAQ removed & Wavetrak fitted...

Last IMSA race I went to a DSG TCR finished 2nd ahead of a bunch of SEQ cars, seems to work just fine--note SEQ cars do not have a wavetrac or any solution anyone uses in street cars. Your linked post doesn't have any collected data. You haven't collected any data yourself. No idea why you are so confident in your opinion here but would love to see any sort of compelling data on why quafie or wavetrac would be an upgrade on these cars. I understand quite a few folks enjoy changing parts on their cars just because but for those interested in going faster I have no reason to believe the aftermarket diff solutions will help you out with that
 

golfdave

Autocross Champion
Location
Scotland (U.K.)
Car(s)
Mk7 Golf GT Estate
Last IMSA race I went to a DSG TCR finished 2nd ahead of a bunch of SEQ cars, seems to work just fine--note SEQ cars do not have a wavetrac or any solution anyone uses in street cars. Your linked post doesn't have any collected data. You haven't collected any data yourself. No idea why you are so confident in your opinion here but would love to see any sort of compelling data on why quafie or wavetrac would be an upgrade on these cars. I understand quite a few folks enjoy changing parts on their cars just because but for those interested in going faster I have no reason to believe the aftermarket diff solutions will help you out with that

Heres another link to a forum member having problems with the VAQ unit when tracking the car..others also chiming in with the same problems....the unit can overheat as the day gets longer, let alone the "delay" it can have.

https://www.golfmk7.com/forums/index.php?threads/vaq-felt-terrible-on-the-track-yesterday.352064/

Besides the info & how it works guides that I have posted, all based on numerous sources of info, the web is full of relevant data on mechanical LSDs like Quaife/Wavetrak & their advantages.

I feel I cannot help you any further.
 
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Oversteermybagel

Go Kart Champion
Location
Boston
Car(s)
mk7 2017 GTi Sport
I play around on maintained grippy surfaces with with big sticky tires from time to time on 100+ deg days, pretty much worse case for the locker. It very well could be experience overheat conditions but it has never thrown a code for me and hasn't shown to be an issue during datalogging. My car is low power so maybe that is why. Would honestly be surprised if it was experiencing thermal runaway because its a very similar unit to what is found in a mk7r which naturally demands more out of the unit. There is no noticeable delay in diff action, it is applying current to the clutch packs well before slip is detected, also no complaints reviewing data logs. Would love empirical data from folks who have played with various diffs but I don't know if that data exists. My biggest complaint is there isn't a particularly good rain map--in the rain it seems to lock too hard.

Heres another link to a forum member having problems with the VAQ unit when tracking the car..others also chiming in with the same problems....the unit can overheat as the day gets longer, let alone the "delay" it can have.

https://www.golfmk7.com/forums/index.php?threads/vaq-felt-terrible-on-the-track-yesterday.352064/

Besides the info & how it works guides that I have posted, all based on numerous sources of info, the web is full of relevant data on mechanical LSDs like Quaife/Wavetrak & their advantages.

I feel I cannot help you any further.

Just checked out your guide. Question about something you wrote:

"What about the “preload” problem?: The worst case scenario for any LSD or the FDL unit is that of "zero load". This could be described as having the car on level ground with all the wheels pointing straight ahead & all on ice, meaning there is no grip/torque difference between the driven wheels."

What does this mean? If there is no grip/torque difference between the driven wheels an open diff = welded diff = VAQ = any differential. There is nothing a diff can do here to help you out here no matter how much it is preloaded.
 

golfdave

Autocross Champion
Location
Scotland (U.K.)
Car(s)
Mk7 Golf GT Estate
I play around on maintained grippy surfaces with with big sticky tires from time to time on 100+ deg days, pretty much worse case for the locker. It very well could be experience overheat conditions but it has never thrown a code for me and hasn't shown to be an issue during datalogging. My car is low power so maybe that is why. Would honestly be surprised if it was experiencing thermal runaway because its a very similar unit to what is found in a mk7r which naturally demands more out of the unit. There is no noticeable delay in diff action, it is applying current to the clutch packs well before slip is detected, also no complaints reviewing data logs. Would love empirical data from folks who have played with various diffs but I don't know if that data exists. My biggest complaint is there isn't a particularly good rain map--in the rain it seems to lock too hard.



Just checked out your guide. Question about something you wrote:

"What about the “preload” problem?: The worst case scenario for any LSD or the FDL unit is that of "zero load". This could be described as having the car on level ground with all the wheels pointing straight ahead & all on ice, meaning there is no grip/torque difference between the driven wheels."

What does this mean? If there is no grip/torque difference between the driven wheels an open diff = welded diff = VAQ = any differential. There is nothing a diff can do here to help you out here no matter how much it is preloaded.

Obviously you haven't fully read or understood that guide that I wrote...

For starters the motorsports VAQ gets 3 maps with different preloads, has a rain map & doesn't use the XDS systems/ or have ABS, only uses the ABS as a passthrough for the sensors

QUOTE:-
The “Electronic modules” specification lists the “ABS/ESP” unit as “Continental” (actually the MK100 unit), & “Software” for the unit as “Not active”. This proves that although the ABS unit is fitted, it is “inactive”. The reason for this is that the ABS unit is required as a “pass through” for sensors:- G44, G45, G46, G47 (ABS wheel sensors), G200 (lateral acceleration sender), G202 (Yaw rate sender), G251 (longitudinal acceleration sender), as the FDL unit requires the data from these to decide to activate or not! Without these is cannot work!
The 2015 Seat Leon Cup racer lists 3 switchable maps available in the control unit of the FDL unit:-
Map 1:-
Base mode, no over slip, only yaw damping above 110km/hr, 300Nm preload during braking. For high grip (new tyres).
Map 2:- Like map 1, less yaw damping, 200Nm preload during braking. Medium grip (used tyres).
Map 3:- Preload dependant on engine torque, 200Nm preload during braking (releasing earlier than Map 2). Low grip/rain.

Please note that this engine has a maximum specified torque of 410Nm, so the FDL unit is applying half, or more, of the engines torque figure as “preload” during braking.
END QUOTE


Regarding the Preload problem you missed this bit in my guide, VAQ/FDL unit first then mechanical LSD:-

QUOTE
How the FDL unit deals with it:-
The FDL unit is not supposed to have this problem as its an electrohydraulic clutch pack diff lock. Unfortunately, it still has a “preload” type problem as it still requires a minimum amount of torque imbalance in Nm between the driven wheels to lock up. If the driven wheels cannot provide enough grip for this then the cars existing XDS+ systems within the ABS unit will be used to apply pressure to the brakes & create a torque imbalance between the driven wheels. This is why it draws heavily on the existing CAN system & sensors.

The FDL unit fitted to the Seat TCR car has an externally adjustable preload setting, with the recommended range being 50Nm (37lbft) to 100Nm (74lbft). Cold measured is 15% higher than warm measure, & preload decreases approx. 15% after 50kms of running. (info from the Seat Leon Cup Racer TCR owners manual)

An Automotive Engineering thesis was conducted in conjunction with Borg Warner AB in Landskrona (Sweden) in 2016. The aim was to develop real world driving scenarios on a test rig so that accurate computer algorithms can be made (instead of having to spend weeks sliding around a test track to get real world data). They did various driveline set ups that the Borg Warner Gen.V unit is used for (AWD, FDL, hang on front, transfer case etc). Unfortunately, they hit problems with the FDL (FXD) set up, quote:- “The FXD system is the most difficult to recreate due to extreme variations in driveline behaviour - The FDL system will not be implemented due to far to rapid driveline behaviour". They also found on the simulated hill tests that, quote:- "the torque that is applied upon the clutch pack coupling is varying a lot when the system oscillates & goes from zero to maximum several times. This affects the whole driveline behaviour". Basically, the unit in this configuration is very “reactive” but also “proactive” i.e. it reacts before. The driveline was oscillating like mad, as the unit tried to figure out which wheel to send the torque to! This resulted in huge differences in the recorded torque & angular velocities. This is all because it takes data from many sources, so is constantly adjusting, more so than in the other configurations & backs up my reasoning as to why they added a “bleed container” to remove air from the oil due to aeration.

Ultimately the FDL unit has no direct mechanical way of activating the clutches, so in effect it has a huge “preload” problem. The FDL cannot “sense” torque through the drive shafts & thus cannot use this to activate the pump to activate the clutch pack. It has to be “told” what the wheel speed is from the ABS sensors as it does not have its own sensors. Therefore, even if you leave the FDL unit powered but disconnect it from the CAN bus or just the ABS unit, it will not work as it is not a “stand alone” unit, & thus NOT a mechanical LSD!

How mechanical LSDs deal with it:-
Mechanical LSDs require a small amount of mechanical force/torque imbalance between the driven wheels to overcome the internal resistance in the LSD unit & start the “lock up” & transfer of torque to the wheel with the most grip. Most modern LSD units get around this with various “bump wave” cogs/ramps, or by altering the end friction plates or the gear oil “W” viscosity rating.

Quaife LSDs rely on several "Bellville" washers (coned) which are set up in an alternating pattern & the friction of gears on the end plate to provide the pre-load. The amount of preload in zero load situations can be adjusted by altering the number/type of washers, or by using a different oil viscosity. According to test results in an engineering thesis paper written on the Quaife LSD, it has "new fresh out of box" preload values of between 13.5Nm to 19Nm (10lbft to 14lbft), with an actual bias of 72% to 95%. Once worn in the Bellville washers give a preload of 5.4Nm to 6.7Nm (4lbft to 5lbft), with an actual bias of 60% to 77%, these values being across all the ranges of acceleration & braking.

Another company called Darkside Developments has an NXG plated LSD with a preload of between 40lbft & max 70lbft, which is similar to the recommended range for the FDL unit.

Wavetrac LSDs have a device in the centre of the diff which responds in zero load situations, quote:- "Precisely engineered wave profiles are placed on one side gear and its mating preload hub. As the two side gears rotate relative to each other, each wave surface climbs the other, causing them to move apart. Very quickly, this creates enough internal load within the LSD to stop the zero axle-load condition." The amount of preload can be adjusted by changing the standard carbon fibre bias plates for ones made from a different material & thus having a different friction coefficient, quote:- "These bias plates provide a mechanism to tune the response of the differential as a function of applied torque load. The applied torque load manifests itself as an axial load from the differential pinions into the housing. This axial force is then considered a normal force into the bias plate, and as a function of the effective coefficient of friction, provide a resistive torque to the rotational motion of the differential pinions. The resistive torque will add to the resistance of relative rotation of all components within the differential. The resistive force, however, is non-uniform since it is a function of the axial load from the differential pinions. The unbalance of the resistive torque will manifest as non-uniform energy absorption within the differential causing a bias ratio.".

I also found a report by someone who had a Quaife LSD in a FWD car & worked with Wavetrac to develop an LSD for his make of car (i.e. used his as a test car). He found that the Quaife was more "on -off" in its transitions whereas the Wavetrac was more neutral/smoother in its transitions.
END QUOTE.
 

Oversteermybagel

Go Kart Champion
Location
Boston
Car(s)
mk7 2017 GTi Sport
Going to ignore a variety of erroneous things stated above (I have the data) none of this is relevant to the question I asked. If a car is on level ground with all the wheels pointing straight ahead & all on ice, meaning there is no grip/torque difference between the driven wheels how am I going to be able to tell the difference between any LSD/locker/differential?
 

TheJokker

Go Kart Newbie
Location
jacksonville
Funny that you can still remove the open diff on the GTI-PP & fit an LSD...yet you're claiming the GTI-PP already has an LSD??..... :unsure:

..therefore fitting two LSDs on a 2WD car??....:unsure:.......:ROFLMAO:..
You are focusing on how it works and not what it does. It does function as a LSD.

Take a look at the top 100 lap times at Nürburgring. A VW GTI Clubsport S with PP is in the top 100 best laptimes (#80). In the right hands it is a very effective LSD. It outperformed "Supercars". Almost everyone would be better served putting their money in other things besides a mechanical LSD if they already have the eLSD.

https://nurburgringlaptimes.com/lap-times-top-100/
 

golfdave

Autocross Champion
Location
Scotland (U.K.)
Car(s)
Mk7 Golf GT Estate
Going to ignore a variety of erroneous things stated above (I have the data) none of this is relevant to the question I asked. If a car is on level ground with all the wheels pointing straight ahead & all on ice, meaning there is no grip/torque difference between the driven wheels how am I going to be able to tell the difference between any LSD/locker/differential?

You originally quoted some of my thread on the VAQ unit the initial section on "Preload" & asked what does it mean....I simple pointed you to the more full explanation in my thread of how the VAQ unit & the mechanical LSD both deal with the problem...if you chose to ignore thoroughly researched & accurate information, that is your prerogative.

As I have stated before I feel I cannot help you further, go and ask somebody else...

You are focusing on how it works and not what it does. It does function as a LSD.

Take a look at the top 100 lap times at Nürburgring. A VW GTI Clubsport S with PP is in the top 100 best laptimes (#80). In the right hands it is a very effective LSD. It outperformed "Supercars". Almost everyone would be better served putting their money in other things besides a mechanical LSD if they already have the eLSD.

https://nurburgringlaptimes.com/lap-times-top-100/

In that case the old 2000yr "EDL "Electronic Differential Lock" ABS based system that VW & Skoda used is an LSD...& so is the current XDS....

The VW Clubsport laptime was a publicity stunt..they had a clear run, numerous tries & a short height very lightweight driver.
 

GTIfan99

Autocross Champion
Location
FL
VAQ is fantastic for street and light track use.

A mechanical LSD is better for frequent track work.
 

TheJokker

Go Kart Newbie
Location
jacksonville
You originally quoted some of my thread on the VAQ unit the initial section on "Preload" & asked what does it mean....I simple pointed you to the more full explanation in my thread of how the VAQ unit & the mechanical LSD both deal with the problem...if you chose to ignore thoroughly researched & accurate information, that is your prerogative.

As I have stated before I feel I cannot help you further, go and ask somebody else...

In that case the old 2000yr "EDL "Electronic Differential Lock" ABS based system that VW & Skoda used is an LSD...& so is the current XDS....

The VW Clubsport laptime was a publicity stunt..they had a clear run, numerous tries & a short height very lightweight driver.
Let's say hypothetically one is building a racing team. One is not going to make their decision of which LSD to use based upon fan boi marketing hype, They are going to base their decision on real world data. VW's work at Nürburgring demonstrates the VAQ is a measurably effective solution to the problems an LSD is designed to address. On one level it was for marketing purposes but it is also "really" happened. They are real laptimes. Most of the other cars in that list also had multiple tries on a clear track.
I can understand your desire to rationalize it away because it destroys your argument that the VAQ is not a real alternative for a high performance car. The Clubsport S at Nürburgring is a real world"proof" that our car can hold it's own with cars costing hundreds of thousands of dollars more.
 

Oversteermybagel

Go Kart Champion
Location
Boston
Car(s)
mk7 2017 GTi Sport
Let's say hypothetically one is building a racing team. One is not going to make their decision of which LSD to use based upon fan boi marketing hype, They are going to base their decision on real world data. VW's work at Nürburgring demonstrates the VAQ is a measurably effective solution to the problems an LSD is designed to address. On one level it was for marketing purposes but it is also "really" happened. They are real laptimes. Most of the other cars in that list also had multiple tries on a clear track.
I can understand your desire to rationalize it away because it destroys your argument that the VAQ is not a real alternative for a high performance car. The Clubsport S at Nürburgring is a real world"proof" that our car can hold it's own with cars costing hundreds of thousands of dollars more.
yah but the driver was unrealistically short 😉
 

golfdave

Autocross Champion
Location
Scotland (U.K.)
Car(s)
Mk7 Golf GT Estate
Let's say hypothetically one is building a racing team. One is not going to make their decision of which LSD to use based upon fan boi marketing hype, They are going to base their decision on real world data. VW's work at Nürburgring demonstrates the VAQ is a measurably effective solution to the problems an LSD is designed to address. On one level it was for marketing purposes but it is also "really" happened. They are real laptimes. Most of the other cars in that list also had multiple tries on a clear track.
I can understand your desire to rationalize it away because it destroys your argument that the VAQ is not a real alternative for a high performance car. The Clubsport S at Nürburgring is a real world"proof" that our car can hold it's own with cars costing hundreds of thousands of dollars more.

If the VAQ is so wonderful for race (as you claim) why did the MQB platform TCR race cars ditch it after only 1yr (only built for the 2015-2016 season)??...

Current spec sheet for the TCR cars...all have:- Differential: multi-plate limited slip differential
https://www.tcr-series.com/homologated-cars/item/volkswagen-golf-gti-tcr-dsg


The Clubsport that set the 'ring laptime had no rear seats, no air con, no sat nav, lightweight battery, manual gearbox, 3 door body, lightweight wing back front seats, semi slick Michelins, "Golf R engine" (265PS with boost to 290PS), & EU unladen weight of 1,285kg....

& Benjamin Leuchter who drove the car weighs circa 60kg...

By comparison a normal GTI-PP (in UK spec as per the Clubsport weight stated above) can weight anything from 1,382kg for a 3door manual to 1,432kg for a 5door DSG & only has 230PS...

& the average GTI-PP driver weighs???...


Basically a normal GTI-PP is 97kg to 147kg heavier by comparison & has 35PS to 60PS less power...All of which will seriously alter the handling, & the acceleration times...

Remove loads of trim & air con from any car, & add more negative camber, add more optimised aero, fit semi slicks, tweek the software, tweek the dampers/springs, fit a more powerful engine & it will go faster around the 'ring.....its NOT solely the VAQ unit....otherwise there would not be such a big difference in the spec of a normal GTI-PP & the one that set the laptime...
 

mrmattolsen

Autocross Champion
Location
Jacksonville, FL
Car(s)
2015 GTI DSG
& Benjamin Leuchter who drove the car weighs circa 60kg...

& the average GTI-PP driver weighs???...
1660767513893.png
 

kep

Go Kart Champion
Location
Boston
Car(s)
Mk7 Golf R, NA Miata
Benjamin Leuchter who drove the car weighs circa 60kg...
I'm 55kg, time to invalidate every single lap time I've ever posted...

This is thread is absolutely wilding out lmao. The semantics of whether or not the VAQ is an LSD are irrelevant. It is proven design capable of transferring torque across wheels. If this design if so terrible, then why does the 911 GT3 RS that just came out today use an electronic diff?

There are obviously downsides to the design, however it clearly works. If you don't have personal experience driving the VAQ on a circuit, why postulate on how effective it is? Opinions don't set lap times.
 
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