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Like most mods, you don't actually need any of them, but........You could apply the same way of thinking and say you only need a Toyota Yaris (Sorry, but driving one of those is enough to destroy your will to live! I know this to be true - I've done so). At first, my perception of a limited slip diff was that it was pointless unless you did trackdays but talking to one or two people with experience of them and also driving my good friend Jason's Mk5 GTI with a VWRacing installed Quaife convinced me otherwise. The fact that VW have now included a LSD, albeit electronic, in the GTI Mk6 acknowledges that traction can be a problem in certain conditions and that applies to standard and not just remapped GTI's with more neddies at the front wheels.
WHAT IS A QUAIFE ATB HELICAL LSD DIFFERENTIAL?Detailed description:
http://www.quaife.co.uk/What-is-a-Quaife-ATB-differentialFurther Info:
http://www.quaife.co.uk/VW-DSG-ATB-diffWHY:To improve traction and ability to grip. This in turn assists handling. It's not quattro but you have to push a car with quattro closer to its limits to have the equivalent 'fun'. The following is quoted from Quaife:
"The Quaife Automatic Torque Biasing Helical LSD Differential enables a car to accelerate more rapidly and corner faster.
How? Simply by getting the power to the ground.
With an normal open differential, fitted as standard on most cars, much precious power is wasted through wheel spin under acceleration.
This happens because the open differential shifts power to the wheel with less grip - along the path of least resistance.
The Quaife differential, however, does just the opposite. It senses which wheel has the better grip, and automatically biases the power to that wheel. It does this smoothly and constantly, and without ever completely removing power from the other wheel.
In cornering, while accelerating out of a turn, the unit biases greater power to the outside wheel, reducing inside-wheel spin.
This allows the driver to begin accelerating earlier, exiting the corner at a higher speed.
The Quaife differential also controls loss of traction when the drive wheels are on slippery surfaces such as ice and snow or mud, providing the appropriate biased traction needed to overcome these adverse conditions. Power is transferred automatically without the use of normal friction pads or plates seen in other limited-slip designs."Why not use a traditional, plate style limited-slip differential?Method one is to use a traditional, plate style limited slip differential, the type of which is used commonly in racing and rallying. This uses a pack of clutch plates worked by sun and planetary gears to transmit a set percentage of the torque to the spinning wheel (say between 40 and 50%.) Certainly these units are effective in increasing traction, but they do have negative implications on both driver enjoyment and vehicle longevity. In some applications on very high performance cars the LSD's clutch plates are now engaged using computer-controlled electro-hydrualic action, with obvious cost implications.
PLATE-STYLE LIMITED SLIP DIFFS:Unless it's set up correctly, a plate-style LSD can ‘snatch' as it suddenly locks to maximum torque transfer. This is particularly noticeable in a front wheel drive car, usually when driven rapidly along a bumpy road, as the vehicle will tend to skip from bump to bump as the LSD tries to transfer the torque to the unloaded wheel. A similar effect will be experienced in a powerful rear wheel car, albeit not felt directly through the steering, but nonetheless this can compromise driver enjoyment.
The traditional style LSD's reliance on clutch plates, as well as sun and planetary gears for operation ultimately leads to wear on these components when used hard. For example, it's not uncommon for high performance track / rally cars to undertake a differential rebuild at least once a season.
THE QUAIFE ATB DIFF:A second mechanical method of improving traction is to use a Quaife Automatic Torque Biasing Helical LSD differential. Rather than using clutch plates as a method of operation, the Quaife ATB Helical LSD uses sets of floating helical cut gear pinions that run in pockets and mesh during normal driving.
Should one of the driven wheels start to spin however, the helical gears start to generate a torque bias thanks to the axial and radial thrust of the helical gear pinions in their pockets. The result is a progressive transfer of torque away from the spinning side of the axle to the driven wheel, which is now capable of transmitting a greater proportion of torque.
Positive Dynamic Effects:Because the Quaife ATB Helical LSD differential's design produces a progressive transfer of torque away from the spinning wheel to the wheel that's capable of driving, the effect is far more benign to the driver. In a front wheel drive car harsh snatching and torque steer are eliminated, so much so that it's not uncommon for a Quaife ATB Helical LSD differential to cope with 400bhp through the front wheels in aftermarket road applications.
SOURCING:On finding that very few workshops had ever fitted the DSG version to the Mk5 GTI, I went to VW Racing who have plenty experience of such things and are obviously used to stripping the 2.0T FSI on a very regular basis. I also asked for price quotations from JKM and APS - Two more workshops I trust but who don't have the same degree of experience. Costs were all within £50 of each other with VWR the most expensive at about £1,500 all inclusive for the DSG version (which costs more than for the Manual gearbox).
INSTALLATION:NOT for the faint hearted! And
NOT recommended to be done by your friendly local neighbourhood garage. It requires a change of filter and specific DSG oil and precision and particular care by the mechanic. However, once installed, it's maintenance free and you can forget it.
Allow 2-3 days overall.
^ I think it's a finely engineered object of great beauty ^
OTHER VERSIONS:American company Peloquin also offer a LSD and their product has a very good reputation and apparently is slightly cheaper. However, I have heard it's not as smooth and, of course, aftersales support will be far better with Quaife/VWR being in the UK.
Quaife Manual and DSG versions are available.
An interesting new diff development is now available from Wavetrac in USA. Info here : -
http://www.vwtuningmag.com/new-wavetrac%C2%AE-limited-slip-differential-from-autotech-driveline/PLUS POINTS:Whether your GTI is standard or performance modified, it will be transformed by the Quaife ATB diff. Once installed you only realise it's there when you discover how its benefits are assisting you to make progress. I haven't driven track where I know it will be even more of an advantage, but on the road and in UK typical bad weather it makes all the difference.
MINUS POINTS:It's not cheap. It will always be limited by your tyres and the road surface conditions - You can still induce wheelspin but it gets controlled far quicker and so much more smoothly without the juddering and grappling for grip. Stocks are sometimes low and can result in a few weeks delay. I can't think of any more minus points and I've now driven about 3,000 miles with it on every type of road and in every type of road condition except snow or ice.
SUMMARY:I feel it's money well spent but it's quite a lot of money at around £1,500. But the same can be said for the AP brakes and suspension mods. In remapping the car, such mods become sensible as they provide improved handling and stopping power. The car wasn't dangerous without these mods (unless, of course, I was to drive it beyond its safe limits) but the car inspires more confidence. That doesn't mean I'm going to drive that much faster but it does mean that I derive even more enjoyment.
I used to sometimes feel disappointed if the roads were wet because I hate wheelspin and loss of traction - it makes me feel that I'm not driving properly - and it would sometimes happen if I didn't take extra care. It's the simple everyday instances such as an exit from a T-junction or at a roundabout when there is lots of traffic and you need to join that traffic flow quickly without scrabbling around. You might say it's a luxury but it does transform the car. When Mark at VWR said "I've now got a date when we can transform your car" my initial thought was crikey, are they going to strip it out? But now I know what they meant.
Someone on another forum pointed out that installing the DSG diff was like my car having open heart surgery and that I'd lose money due to not being able to resell it separately. But my attitude is that I'm keeping this car awhile and it's all done purely for my enjoyment and even my safety. Anyway, who in their right mind is going to say they'll buy my car only if I put back a stock diff!? One day it'll either be someone who wouldn't know it was fitted anyway but liked the car's handling. Or it'll be an enthusiast who says: "She's got a Quaife? Ooooooh! Yes pleeeeease!!". VWR installed new bearings too - I think I just extended that part of my car's life!
The latest Mk6 GTI has an electronic limited slip diff called XDS as part of the ESP but I trust a purely mechanical one more. The ESP is 'led' by whatever the Quaife reacts to physically on the road and not the other way around via sophisticated sensors.
Most young dudes would rather spend their money on a remap because the returns feel so much more obvious but I would recommend the Quaife ATB diff as much more beneficial, unless you like wheelspin!
