996 GT3 Diff Plates: Standard or Motorsport?
Discussion
I'm interested in the experiences of those who have replaced the diff plates in their 996 GT3: did you choose motorsport parts, or standard?
What have you found to be the benefits and downsides of your choice?
- cost
- longevity
- driving characteristics (especially on the road)
Any and all insights gratefully received.
What have you found to be the benefits and downsides of your choice?
- cost
- longevity
- driving characteristics (especially on the road)
Any and all insights gratefully received.
jeremyc said:
What have you found to be the benefits and downsides of your choice?
- cost
- longevity
- driving characteristics (especially on the road)
Motorsport; it's all good, there are no downsides - cost
- longevity
- driving characteristics (especially on the road)
Cost - same
Longevity - 46K miles / 70 trackdays & still going strong
Driving characteristics - Err, the diff actually works properly when the car is used as intended (as opposed to being garaged & polished, as many seem to be)?
nxi20 said:
jeremyc said:
What have you found to be the benefits and downsides of your choice?
- cost
- longevity
- driving characteristics (especially on the road)
Motorsport; it's all good, there are no downsides - cost
- longevity
- driving characteristics (especially on the road)
Cost - same
Longevity - 46K miles / 70 trackdays & still going strong
Driving characteristics - Err, the diff actually works properly when the car is used as intended (as opposed to being garaged & polished, as many seem to be)?
Any other changes to setup you made to accommodate the motorsport diff plates?
Motorsport. No noticeable difference in road driving except back end can hop a bit in very tight turns (or drift if you use the throttle!). On track works as you would expect - rock steady back end under braking. Just watch oversteer on turn in if you do so off the throttle, the back will step out (very gently) much more than it tends to with standard diff. If you turn in under throttle you may get a tad more understeer, but I never noticed it as I tend to trail brake slightly and - because of the above - found turn in much crisper with new diff.
nxi20 said:
Motorsport; it's all good, there are no downsides
Cost - same
Longevity - 46K miles / 70 trackdays & still going strong
Driving characteristics - Err, the diff actually works properly when the car is used as intended (as opposed to being garaged & polished, as many seem to be)?
nowt wrong with a bit of polish Nick ;-)Cost - same
Longevity - 46K miles / 70 trackdays & still going strong
Driving characteristics - Err, the diff actually works properly when the car is used as intended (as opposed to being garaged & polished, as many seem to be)?
David
nxi20 said:
Motorsport; it's all good, there are no downsides
Cost - same
Longevity - 46K miles / 70 trackdays & still going strong
Driving characteristics - Err, the diff actually works properly when the car is used as intended (as opposed to being garaged & polished, as many seem to be)?
Agreed +1Cost - same
Longevity - 46K miles / 70 trackdays & still going strong
Driving characteristics - Err, the diff actually works properly when the car is used as intended (as opposed to being garaged & polished, as many seem to be)?
It's a no-brainer.
jeremyc said:
hanks - did you find the locking action stronger than standard and did you feel the need to change any of the cars setup to compensate, perhaps to dial out increased understeer?
Any other changes to setup you made to accommodate the motorsport diff plates?
What's the difference between the plates themselves? Are they both plain steel or is one set sintered material?Any other changes to setup you made to accommodate the motorsport diff plates?
The locking action is surely a function of the ramp angles on the acceleration and deceleration actions respectively and the amount of preload put on the plataes via the belleville washers?
Are the ramp angles easy to modify on the 996 diffs? This would allow you to help tune out entry understeer characteristics and also how the diff behaved when under load (i.e. acceleration).
Steve Rance & Neil (Fioran0) - are you out there anywhere? fergus said:
What's the difference between the plates themselves? Are they both plain steel or is one set sintered material?
The locking action is surely a function of the ramp angles on the acceleration and deceleration actions respectively and the amount of preload put on the plataes via the belleville washers?
Are the ramp angles easy to modify on the 996 diffs? This would allow you to help tune out entry understeer characteristics and also how the diff behaved when under load (i.e. acceleration).
Steve Rance & Neil (Fioran0) - are you out there anywhere?
The friction disc material is more aggressive, and I think the motorsport items also use a higher preload/thicker discs in addition to a higher preload belville washer as the Guards Transmission internals do. Changing the ramp rates isn't often done although I did on mine because the C2 ramp rates are pretty low compared to the GT3 rates.The locking action is surely a function of the ramp angles on the acceleration and deceleration actions respectively and the amount of preload put on the plataes via the belleville washers?
Are the ramp angles easy to modify on the 996 diffs? This would allow you to help tune out entry understeer characteristics and also how the diff behaved when under load (i.e. acceleration).
Steve Rance & Neil (Fioran0) - are you out there anywhere? Sorry for chiming in so late, I'm on holiday and am Internet-less coupled to intermittent phone signal.
It makes no sense not to use the Motorsport diff plates IMHO. The street plates are extremely soft and don't cope with any heat at all. The result is that street driving will wear it out pretty quickly, track driving will wear it out unbelievably so. A weekend could easily be enough.
The Motorsport plates are an entirely different composition (harder and more aggressive) being built for track duty. The result is that they will both last a good amount of time before wearing out whilst the heat from track use won't just see them expire like it does the street plates.
As for performance, by just fitting the plates to replace worn street ones any behaviour change will be minimal; other than of course now having a fully working diff and access to all the benefits listed above. It will make you realise just how poorly the diff as fitted was operating though.
The diff fitted to the Cup cars carries quite a few other changes over the street version. Only by fitting all these too will you start changing the character of the diff along with introducing potential street driving headaches.
It makes no sense not to use the Motorsport diff plates IMHO. The street plates are extremely soft and don't cope with any heat at all. The result is that street driving will wear it out pretty quickly, track driving will wear it out unbelievably so. A weekend could easily be enough.
The Motorsport plates are an entirely different composition (harder and more aggressive) being built for track duty. The result is that they will both last a good amount of time before wearing out whilst the heat from track use won't just see them expire like it does the street plates.
As for performance, by just fitting the plates to replace worn street ones any behaviour change will be minimal; other than of course now having a fully working diff and access to all the benefits listed above. It will make you realise just how poorly the diff as fitted was operating though.
The diff fitted to the Cup cars carries quite a few other changes over the street version. Only by fitting all these too will you start changing the character of the diff along with introducing potential street driving headaches.
Edited by fioran0 on Friday 13th July 00:36
fergus said:
What's the difference between the plates themselves? Are they both plain steel or is one set sintered material?
The locking action is surely a function of the ramp angles on the acceleration and deceleration actions respectively and the amount of preload put on the plataes via the belleville washers?
Are the ramp angles easy to modify on the 996 diffs? This would allow you to help tune out entry understeer characteristics and also how the diff behaved when under load (i.e. acceleration).
Steve Rance & Neil (Fioran0) - are you out there anywhere?
Fergus,The locking action is surely a function of the ramp angles on the acceleration and deceleration actions respectively and the amount of preload put on the plataes via the belleville washers?
Are the ramp angles easy to modify on the 996 diffs? This would allow you to help tune out entry understeer characteristics and also how the diff behaved when under load (i.e. acceleration).
Steve Rance & Neil (Fioran0) - are you out there anywhere? The street car uses carbon as its friction material (though I've heard one year of 996 had brass, but haven't seen). It's very soft and even a small amount of heat just polishes it off. Even when new it doesn't bite very much tbh. I've seen plates pulled from a street GT3 diff that was completely shot but the plain plates still had the tooling marks on them. The friction surface hadn't even managed to add swirl marks enough to cover these over 20k miles. The friction material was still plenty thick, just very smooth.
The motorsport plates have some sort of secret sauce for the friction material (looks like a moly). It lasts longer, doesn't expire in heat and is much more aggressive in terms of bite. Pattern on the friction disc is different too (and cup uses more stacked in the diff)
Absolutely ref the locking. The plates only allow the diff to actually lock, not how it locks. This is why adding Motorsport plates is such a good addition. You don't physically change the diff behaviour, just allow it to lock when it tries to.
The diff fitted to the Cup uses huge amounts of preload compared to the street car. Street allows for 5-15Nm preload. Cup is 90-100Nm. There's a good variety of washers available to allow street cars to run a bit more preload if they want without having to jump to cup belleville washers.
Ramp angles are easily changed, a few suppliers offer alternatives. Theres quite a few people running 50/80 diffs instead of stock 40/60 on street cars that now see heavy track use. Most race series for the Cups don't allow changes to ramp angles so it's an avenue that's relatively unused here.
As Steve said, it's braking where the diff is absolutely critical on these cars and the first place you feel it when it stops doing its job.
fioran0 said:
Fergus,
The street car uses carbon as its friction material (though I've heard one year of 996 had brass, but haven't seen). It's very soft and even a small amount of heat just polishes it off. Even when new it doesn't bite very much tbh. I've seen plates pulled from a street GT3 diff that was completely shot but the plain plates still had the tooling marks on them. The friction surface hadn't even managed to add swirl marks enough to cover these over 20k miles. The friction material was still plenty thick, just very smooth.
The motorsport plates have some sort of secret sauce for the friction material (looks like a moly). It lasts longer, doesn't expire in heat and is much more aggressive in terms of bite. Pattern on the friction disc is different too (and cup uses more stacked in the diff)
Absolutely ref the locking. The plates only allow the diff to actually lock, not how it locks. This is why adding Motorsport plates is such a good addition. You don't physically change the diff behaviour, just allow it to lock when it tries to.
The diff fitted to the Cup uses huge amounts of preload compared to the street car. Street allows for 5-15Nm preload. Cup is 90-100Nm. There's a good variety of washers available to allow street cars to run a bit more preload if they want without having to jump to cup belleville washers.
Ramp angles are easily changed, a few suppliers offer alternatives. Theres quite a few people running 50/80 diffs instead of stock 40/60 on street cars that now see heavy track use. Most race series for the Cups don't allow changes to ramp angles so it's an avenue that's relatively unused here.
As Steve said, it's braking where the diff is absolutely critical on these cars and the first place you feel it when it stops doing its job.
NeilThe street car uses carbon as its friction material (though I've heard one year of 996 had brass, but haven't seen). It's very soft and even a small amount of heat just polishes it off. Even when new it doesn't bite very much tbh. I've seen plates pulled from a street GT3 diff that was completely shot but the plain plates still had the tooling marks on them. The friction surface hadn't even managed to add swirl marks enough to cover these over 20k miles. The friction material was still plenty thick, just very smooth.
The motorsport plates have some sort of secret sauce for the friction material (looks like a moly). It lasts longer, doesn't expire in heat and is much more aggressive in terms of bite. Pattern on the friction disc is different too (and cup uses more stacked in the diff)
Absolutely ref the locking. The plates only allow the diff to actually lock, not how it locks. This is why adding Motorsport plates is such a good addition. You don't physically change the diff behaviour, just allow it to lock when it tries to.
The diff fitted to the Cup uses huge amounts of preload compared to the street car. Street allows for 5-15Nm preload. Cup is 90-100Nm. There's a good variety of washers available to allow street cars to run a bit more preload if they want without having to jump to cup belleville washers.
Ramp angles are easily changed, a few suppliers offer alternatives. Theres quite a few people running 50/80 diffs instead of stock 40/60 on street cars that now see heavy track use. Most race series for the Cups don't allow changes to ramp angles so it's an avenue that's relatively unused here.
As Steve said, it's braking where the diff is absolutely critical on these cars and the first place you feel it when it stops doing its job.
Hi. Thanks for the detailed reply. I'm surprised that the carbon plates wear out very quickly. The current in-vogue plate diff for caterhams, is a Titan unit, where the uprated version uses carbon plates (rather than steel). These simply do not wear, even with >300hp applications.
The preload for a Caterham plate diff is around 25lbs ("trackday" use). I'm surprised a heavier, torqier car like the GT3 with more mechanical grip (i.e. tyre footprint) uses such a light preload. Does such a small preload mean the action of the diff is extremely benign? I've only driven a Manthey GT3 on the 'Ring, and as it wasn't mine, I wasn't pushing it hard enough to feel the diff working, so couldn't tell how aggressive it was.
A decel ramp of 60 degrees is fairly tame, but as Steve said, taming the rear on turn in, esp. while trail braking is paramount in terms of ramp angle spec., and hence diff behaviour.
fergus said:
Neil
Hi. Thanks for the detailed reply. I'm surprised that the carbon plates wear out very quickly. The current in-vogue plate diff for caterhams, is a Titan unit, where the uprated version uses carbon plates (rather than steel). These simply do not wear, even with >300hp applications.
The preload for a Caterham plate diff is around 25lbs ("trackday" use). I'm surprised a heavier, torqier car like the GT3 with more mechanical grip (i.e. tyre footprint) uses such a light preload. Does such a small preload mean the action of the diff is extremely benign? I've only driven a Manthey GT3 on the 'Ring, and as it wasn't mine, I wasn't pushing it hard enough to feel the diff working, so couldn't tell how aggressive it was.
A decel ramp of 60 degrees is fairly tame, but as Steve said, taming the rear on turn in, esp. while trail braking is paramount in terms of ramp angle spec., and hence diff behaviour.
Hey Fergus,Hi. Thanks for the detailed reply. I'm surprised that the carbon plates wear out very quickly. The current in-vogue plate diff for caterhams, is a Titan unit, where the uprated version uses carbon plates (rather than steel). These simply do not wear, even with >300hp applications.
The preload for a Caterham plate diff is around 25lbs ("trackday" use). I'm surprised a heavier, torqier car like the GT3 with more mechanical grip (i.e. tyre footprint) uses such a light preload. Does such a small preload mean the action of the diff is extremely benign? I've only driven a Manthey GT3 on the 'Ring, and as it wasn't mine, I wasn't pushing it hard enough to feel the diff working, so couldn't tell how aggressive it was.
A decel ramp of 60 degrees is fairly tame, but as Steve said, taming the rear on turn in, esp. while trail braking is paramount in terms of ramp angle spec., and hence diff behaviour.
Sorry for not being clearer, the friction material doesn't usually wear down to the bone. It just stops grabbing at all after a short while while heat makes it go positively slippy despite their being actually plenty material thickness left. A Cup diff or diff with motorsport plates will show plenty of swirls from working while it's common for a totally finished street one to look like its never worked at all.
Are the caterham carbon plates carbon on carbon rather than carbon on metal as per the porsche diff though? If so then they should work great.
Diff plates are the same principle as a regular clutch and interestingly carbon on metal for a clutch application works horribly and with the exact same results as in the porsche diff. Carbon/carbon works amazingly with ceramettalic/metal only just behind but combine carbon and metal and you get left stranded.
Preload really only impacts how the diff reacts/transitions. Until the ramps kick in its running open no matter what preload so the street setup uses a "low" value to give it a smoother transition which makes sense given its designed for road use. Under lock and when working (ie with proper plates) it isn't benign.
Porsche use % lock up for their diffs rather than ramp angles just to keep things muddy
The 40/60 seems to work pretty well. Weight transfer/balance and traction etc all interplay with the diff needs. The 996 is actually pretty advantaged under braking and accel due to its rear engine so doesn't need more. Of course other cars have very different characteristics and need a diff setup for this.
The newer RSR uses 45/65 now so a slight shift but not much.
Street 997GT3 uses 28/40 instead of the 40/60 of the 996 and race cars.
Edited by fioran0 on Friday 13th July 14:08
Steve Rance said:
The ramp set up is very important. I drove an RS at spa with a hideous set up, it felt like the rear of car was being hit by a sledge hammer as I turned in. It was so bad it was dangerous. Other cars snap into oversteer immediately as you turn in because the plates are so worn, they are basically ineffective.
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