LSD Group order ?

Originally Posted by Trailbraker

BTW Brendan the restricted invite track day I mentioned at Mondello is on next Sat 16th September. Let me know if you want a guest/passenger slot.
(I have one slot left).

Thanks TB, I'm most grateful for the offer. I'll try to confirm one way or another before wednesday night, if the place is still available at that stage.

Ok....now I am confused..

AFAIK any type of 1 way Limited slip Diff will not work if one wheel does not have any traction? Otherwise we are talking locking diff (as in off road vehicles) or very very agressive diffs not suited for Road use. (2 way diff)

I think the AD LSD would also stop working of one wheel looses all traction? (assuming its a 1 way diff) Since the Clutch type LSD works by the combination of Torque from engine and traction from wheels, then loosing all traction on one wheel is effectively the same as sudden thottle lift off, in which case the diff should unlock immediately?

Maybe the Clutch type is only activated via Torque from engine? In this case I wold say this type seems significantly more dangerous in the event of one wheel completely loosing traction, not mentioning the risk of damaging drive shafts and other components when the wheel regains traction while full power is still transfered to it.

Originally Posted by Trailbraker

Quaiffe diffs also have zero locking capabilities so once any wheel is totally unloaded they stop functioning, there is a sudden torque transfer when the wheel regains effective contact with the ground.

So in theory they certainly can cause increased torque steer, that doesn't mean that they always will.

My own progressively locking diff hugely reduced torque steer for my car despite a lot of extra torque over standard.

Cheers,
TB

Originally Posted by Peter K

Ok....now I am confused..

AFAIK any type of 1 way Limited slip Diff will not work if one wheel does not have any traction? Otherwise we are talking locking diff (as in off road vehicles) or very very agressive diffs not suited for Road use. (2 way diff)

Clutch type LSDs lock - Thats how they work!

They progressively limit the difference in the rotational velocity between the two wheels.
e.g. mine is set at 30% locking factor.
So the unloaded wheel in a corner can spin up to 30% faster than the outside wheel.
The locking of the faster spinning wheel to a fixed proportion of the other wheels rotation forces torque to be transferred to the outside wheel under cornering, even if the inside wheel is airborne...
i.e. the rotation velocity of the two wheels is locked together up to a fixed proportion.

This is NOT the same as a welded diff which would just cause huge understeer everywhere in an FWD, and huge oversteer everywhere in a RWD

When you say off road vehicles you are probably thinking of locking diffs that cause understeer when the two wheels rotational velocity is locked together completely..
These aren't really comparable to progressively locking performance oriented diffs. Their main job is usually to just avoid wheelspin to allow some behemoth to get out of a pile of mud.

I believe "1 way", "2 way" and "2 and a half way" diffs just refer to the level of differentiation under braking as well as under acceleration.
1 way diffs only function under acceleration as opposed to braking.

I think the AD LSD would also stop working of one wheel looses all traction?

No, the two wheels rotational velocity are coupled within a certain proportion.
This is hugely different to a torque sense diff such as Quaiffe that limits the proportion of torque transfer to a certain proportion.
e.g. For an ATB torque bias ratio of 8:1 the torque can only be transmitted in a max split of 8:1 between the two wheels.

In summary one limits the rotational wheelspeed difference,
the other limits the torque split proportion.

Maybe the Clutch type is only activated via Torque from engine? In this case I wold say this type seems significantly more dangerous in the event of one wheel completely loosing traction, not mentioning the risk of damaging drive shafts and other components when the wheel regains traction while full power is still transfered to it.

On the contrary - I believe you have just described the main disadvantage of torque sensing diffs such as Quaiffe
Since they are technically incapable of limiting the proportional difference of rotational velocity between the two wheels (like a locking clutch type LSD can), an airborne wheel will spin up to high speeds and theoretically cause huge stress when it lands.
Some googling will probably find lots of statements of this characteristic, with another example being when you have one wheel on grass on one on tarmac.. and then rejoin the track, again a sudden transfer.

That said Quaiffe specifically offer a lifetime guarantee even for track use so their parts must be pretty well made.
(although I presume the guarantee just covers replacement rather than other damage).

Cheers,
TB

TB,

Not sure you are giving the Quaife unit credit where credit is due, and i can't quite make ends meet or fully grasp in what you write here.. -I will have to do some reading i think!

Let me quote from the Quaife webiste. Of course I am not in a position to say if their claims is BS, but I would not expect it to be so.



The differential progressively locks as torque increases; there are no plates or clutches to wear out as more conventional limited-slip designs. Is particularly effective in combating the effects of FWD torque steer.



I can certainly vouch for the fact that it works progressively. During normal driving you dont even sense the LSD is there. Only when pushing the car you can feel it working, and indeed hear it tick..The harder you push the car in corners, the more you can feel it working.



The QUAIFE is great for street driving or racing. Racers don't have to put up with locking mechanisms or spools that tear the steering wheel out of their hands when cornering. Because it behaves like an open differential during ordinary driving, street drivers will have trouble telling it's there until pushing the cars limits.



This last point is ecatly what i wanted to avoid. Having a road car lock up or "tear the steering wheel out of my hands" is way too agressive IMO. I also noted what "The Stig" Via Clarkson commented in TopGear after he drove the AD 147 3.7 round the track in that Phantom 1.30 lap time. Can't remember the exact wording, but it was something about it "wrenching your arms out" when going into a corner with too much power. I have to admit that statement plus the added service costs of a cluch based LSD is what initially put me off the AD unit.

I am going to have to get back to you all on this theory of the Quaife unit not working or working too much when one wheel in not touching the ground. In my book of logic, the ATB type LSD will transfer power from the wheel spinning in open air to the wheel still on the ground or just release any added power exactly because it does NOT lock.. This is somewhat supported in what is written by quaife themselves.



The QUAIFE 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. The QUAIFE ATB Differential provides constant and infinitely variable drive. Power is transferred automatically without the use of normal friction pads or plates seen in other limited-slip designs

Heres a good explanation that mentions how good a Quaiffe diff is, (btw I'm not saying they aren't good ) but also has an excellent explanation of its inability to work when a wheel off the ground.

http://www.sportcompactcarweb.com/pr...us_zx3_part_4/

The amusing thing about the Quaife site is that obviously their marketing folk had to explain that the biggest disadvantage of a Quaife diff (inabaility to lock) was actually a safety feature.

The "dangerous locking" they are referring to is the fact that with a RWD car a locking diff allows you to do power oversteer more effectively than with a torsen diff.
For sporty RWD cars, most people would think that this is a good thing, which is why all the M series BMWs to take a well known example have a locking diff.

For FWD cars obviously you aren't going to spin because of the locking effect of the diff, its just maximizing the effective torque the laden wheel can receive.

Locking for a clutch type diff isn't a dramatic "lock up" like I think you might be considering, its a progressive coupling of rotational velocities.
Generally you wouldn't even notice it occuring in terms of tugs on the wheel.
The cornering line of the car might tighten nicely as the diff takes hold but thats about it for my setup at least.

Cheers,
TB

I dunnoTB... gonna stick to my guns on this one The more i read about the differences, the more i am convinced that the Quaife Automatic Torque Bias approach is the right way to go for a car like the GTA. As you mention M cars are fitted with locking diffs, which sugggests it is a wise choice, but then again the Noble M12 is fitted with the Quaife LSD so.....

The issue of one wheel not touching the ground is not a factor with road going race cars, but mainly a concern for Rally cars. I mean when was the last time one of your front wheels was not firmly planted on the ground?

Also the Quaife does not stop to work when one wheel is lifted of the ground, it just reduces power to that wheel. It does not remove all torque from it. It "Backs off on the power" so to speak..

Ok granted it will then apparently stop to act like an LSD, but that does not make it unsafe or prone to damaging any parts when the wheel again has contact to the ground. The question also remains as to wether or not it will back off on power from the wheel still on the ground. I dont think that is the case, sp even if the inside wheel lifts off the ground during a hard turn, the outside wheel still has a lot of extra power sent to it by the time it starts to work as an open diff.

There should be no sudden burst of torque going to a wheel at "touchdown" since the Bias is endlessly progressive. (up to the max bias setting anyway) Hopefully the diff senses the traction or lack of it, and adjusts accordingly.

Also the automatic Torque Bias is mentioned several places as being perfect for helping cure powerfull FWD cars of Torque Steer, so i dont know why it should do the opposite? Where in the design is it in your opinion that the ATB would cause more torque steer?

Originally Posted by Peter K

The issue of one wheel not touching the ground is not a factor with road going race cars, but mainly a concern for Rally cars. I mean when was the last time one of your front wheels was not firmly planted on the ground?

It happens regularly when I go over a kerb on track..

It would also happen if you are turning in strongly enough to **** the inside wheel slightly, this is less likely with stiffer suspension or lowering, but a race driver pal had no problems doing it on a tricky corner at Mondello when demoing GTAs on standard suspension.

Originally Posted by Peter K

Also the Quaife does not stop to work when one wheel is lifted of the ground, it just reduces power to that wheel. It does not remove all torque from it. It "Backs off on the power" so to speak..

It works exactly like an open diff when one wheel has no traction.
Some googling should find hundreds of references to this characteristic.
IT doesn't make the quaiffe a bad choice and I'm not at all suggesting it is.

BTW apparently its a favourite trick of FWD quaife diffed cars to use very light left foot braking under cornering to bring back some load to get the diff working again.

Originally Posted by Peter K

Ok granted it will then apparently stop to act like an LSD, but that does not make it unsafe or prone to damaging any parts when the wheel again has contact to the ground. The question also remains as to wether or not it will back off on power from the wheel still on the ground. I dont think that is the case, sp even if the inside wheel lifts off the ground during a hard turn, the outside wheel still has a lot of extra power sent to it by the time it starts to work as an open diff.

There should be no sudden burst of torque going to a wheel at "touchdown" since the Bias is endlessly progressive. (up to the max bias setting anyway) Hopefully the diff senses the traction or lack of it, and adjusts accordingly.

Well, how do you think an open LSD behaves in these situations?
Have you ever got one wheel on the grass under power without an LSD, you need to be awake!

True there isn't a sudden burst of torque when the wheel *touches down*, but there is a sudden burst of torque when the wheel becomes airborne which means that when it touches down it will be spinning faster than the grounded wheel..

Torque bias transfer in a quaife diff is instant (and continuous).
Aren't "instant" and "progressive" mutually exclusive in this context .
Yes this is a major advantage for sporty driving when your wheels are on the ground.

Originally Posted by Peter K

Also the automatic Torque Bias is mentioned several places as being perfect for helping cure powerfull FWD cars of Torque Steer, so i dont know why it should do the opposite? Where in the design is it in your opinion that the ATB would cause more torque steer?

I'm not saying that your diff does cause torque steer for your use, I'm just saying that depending on how Quaife setup the diffs they can cause torque steer.
The reason is simple they transfer torque instantly.
Any mention of progressiveness is being disingenous since Quaife diffs imply *instant* torque bias transfer..
..and yes, this is extremely efficient for FWD cars that have their two wheels on the ground.

Why could this ever cause torque steer?
Well if you have an **instant** transfer of torque AND the diff was set with an aggressive torque bias ratio you can potentially get an instant transfer of a large proportion of torque.
Does this not seem logical?
Its just a technical characteristic of the design.

BTW since you mentioned what Jeremys said (that the Stig said ) about the AD diff, you might be interested to see what he actually said after he had personally driven the Autodelta 147 car on country roads in comparison to the Focus RS Quaife diff.

Originally Posted by Peter K

they’ve (Autodelta) fitted a limited-slip differential, and that started the alarm bells ringing even more stridently. Ford fitted such a thing to its Focus RS and turned what might have been quite a nice car into a complete liability. On anything other than a smooth track it would suddenly turn sharp left for no reason. And you couldn’t prepare yourself, because sometimes it would suddenly turn sharp right. Limited slip diffs in front-wheel-drive cars, I deduced after a sweaty, terrifying drive through Wales in the RS, Do Not Work.

Following on the same article he mentions the AD diff :

Originally Posted by Jeremy Clarkson

A corner was coming. And then it was a distant speck in my rear-view mirror. I vaguely remember turning the wheel and I have a dim recollection of being astounded by the grip . . . and then the moment was gone.

No, really, the damn thing’s a barnacle. Normally, in a tight bend, a front-drive car will spin the inside wheel uselessly, which means the one on the outside suddenly has to do all the steering and power-handling. But obviously it can’t and you understeer off the road. But with that diff, the inside wheel doesn’t spin, it grips and grips and then it grips some more.

Cheers,
TB

So I've called Quaife and spoke to one of their Engineers, and I called a Friend who has done some years of Rallying with Peugeots. Gotta get to the bottom of this!

Firstly the Quaife ATB does indeed act like an open diff if one wheel is lifted off the ground, meaning it will transfer power from the loaded wheel to the unloaded wheel. But(And the engineer agreed on this point) This whole discussion is virtually irrelevant, since you are not going about lifting one wheel off the ground, especially not on FWD cars. It might be that you TB is advanced enough to be lifting one front wheel a lot, but on the other hand i've not done so even once since i installed my Quaife unit last year. I've done 9-10 Trackdays since, and 25k km.

Soon after i fitted the Quaife diff, i discovered that by adding power earlier then before. (before apex) i would ge the diff working and thus having the benefit of the diff though most of the corner. I guess that is my instinctive way of dealing with how the quaife lsd works. I am not advanced enough to be left foot braking in turns yet, although it is a point which i have been trying to learn lately.

In general i always avoid kerbs unless they are flat like that one at wipperman at the Ring I dont think it is worth ruining my car to gain one second per lap..

Even if were in this rahter extreme situation with one wheel off the gournd, then it should not a point which can be used to speak against the Quaife and for the Clutch type, since a Clutch type diff wiill cause the car to understeer even more with one wheel off the ground.

As a rule I have been told that the Clutch type Diffs creates more understeer as opposed to the Quaife type, which should help reduce understeer. My friend the Rally driver explained this point, and the guy from Quaife also touched on this.(albeit he would speak for the Quaife type) Note that my friend is familiar with Clutch type Diffs, and pointed out that understeer is not very important in rallying since the you do not rely on grip, but rather "place" the car. For this reason he would opt for a locking diff for rally type driving, but the Quaife type for recreational trackday driving.

He also mentoned that you have to set the car up right in a more precise and particular when dealing with the Clutch type diffs, making them more sophisticated to install, demanding a more precisely matched suspension. For someone getting a clutch type diff installed without having the expert around to match the rest of the car to the diff, does not sound like a good situation for those of us not having access to the Expert knowledge of AD's staff .

This whole point of the thread has been to organize a potential Group order, so i think it is important that we try to view this as subjective as possible, Ie. what type of diff is most suited for the potential AO buyer.

Now i also asked the Engineer from Quaife abut the Clarkson-Focus RS incident. He explained to me that Clarkson illustrated the problem by setting up the ideal siatuation for the diff to create torque steer.

Meaning that the Focus was going up a steep and bumpy road while accelerating hard. Effetively this is taking all the weight off the front wheels, causing the diff not to work/act like an open diff. Under this scenarion, the car would act erratic like you see. I can personally vouch for the fact that my 3.2 with the Quaife does not have any torque steer issues when accelerating hard on a bumpy b-roads. Mind you I've not tried to do this while going up a steep hill, but I will definitely try it as soon as i can do so safely. Would be interesting to see if my car would do the same type of weaving from side to side as the Focus RS did

It is my opinion (at this point anyway) that a clutch type is too agressive/advanced for 90% of the GTA owners here on AO. I do a lot of Trackdriving myself, and even I think it appears to be a tad OTT. I personally like the fact about the Quaife LSD's, that there is no service requirements after it is installed., and that in everyday driving you don't hear or feel it. It might be that you lose the LSD benefits if one wheel is off the ground, but as mentioned that is not an issue for me personally. It is really hard for me to see the benefits of a clutch type LSD over the Quaife type.

I've not had the chance to try a Clutch type in real life. other then as a passenger in your car, and boy was i impressed! No doubt your car is amazing and leagues above my 3.2, but i wonder if this is not a result not so much from the diff itself, but more the overall package of you car, which appears to have been honed to perfection by AD and you? Maybe you could have gotten the same or even better results with a quaife type LSD?

Hopefully I might get a chance this comming weekend to try out a car with the AD diff. AD is bringing a few of their cars to Zandwoort.

Meanwhile i hope you TB, can get a chance to try out bmoferrall's car..? It would be ideal for the concensus if both of us could bring our expereinces with "the other type" to the thread. Certainly these past two days have given me a lot more insight to the differences, so now more then ever I am interested in comparing the two types. I still need to decide which type i want for the GTA, and I want to keep an open mind.

Bringing out the heavyweights eh?

Very interesting, I don't think most of what you/they said is in conflict with my points, which to be honest really were just intended to illustrate the technical differences between the diffs rather than suggest which one was better than the other for any AO'er

i.e. they were in direct reply to a question about why I had mentioned to bmofferral off-board that there was a potential for torque steer.
I hadn't meant to get into such a detailed pro and con

I'm not sure I undertand the point below though

Originally Posted by Peter K

Even if were in this rahter extreme situation with one wheel off the gournd, then it should not a point which can be used to speak against the Quaife and for the Clutch type, since a Clutch type diff wiill cause the car to understeer even more with one wheel off the ground.

RE the abovbe: I can't see how having maximally effective drive to the outside wheel under cornering will create understeer, it actually helps rotate the car.
Unless you mean that you have the potential through clumsy throttle control to overload the outside tyre with push understeer - thats true; ..but you have complete control over it
With an open diff, you can't drive the grounded wheel as effectively.
On a track unloading a wheel mounting a kerb happens exactly at the apex when you would like to be getting on the throttle, and being able to get on the throttle earlier is an advantage.

Originally Posted by Peter K

As a rule I have been told that the Clutch type Diffs creates more understeer as opposed to the Quaife type, which should help reduce understeer.

The above point is true to an extent depending on the tightness of the corner, but is tunable by the locking percentage of the diff.
e.g. You can see this if you had 100% locking, you would have huge understeer for sure in a FWD car.
It would be undrivable!
With a 30% difference allowed in wheelspeeds I don't know how much that holds true for the average corner though, might be an issue for hairpins?
..and possibly not at all for a GTA with its hilarously large turning circle.
It probably can't turn tightly enough anyway to encounter this limitation

Anyway am enjoying your quest for the truth!

TB

Well actually i think it is a question of which is most suited or best if you will. Very much so for me personally, since i don't mind paying a little extra if it brings me the better result, and i have the highest repect for your car. I've experienced it first hand!

All this talk of how the different types work can be very theoretical. F.ex i was not aware that using left foot braking would engange the Quaife ATB to a higher degree if I was in a situation where negotiating a corner means that one front wheel might lift off. This is very advanced driving techniques, and not something i think most of us here is able to apply in real life sitations. So while it might be true, it might not be so relevant, and probably confuse or scare people away from investing in a LSD. As i mentioned earlier, instinctively i solved the problem by adding power before Apex, and always having both wheels on ground. This technique seems both safe, and is very much quicker and elegant then a how a stock GTA/V6 negotiates corners.

On the other hand i am myself scared by the outlook of installing something which might lock the steering wheel in a fixed position while the car is understeering madly into the undergrowth... This is probably highly exaggerated, but none the less the impression you get if you listen to these extreme scanarios where Cluch type LSD's locks up mid corner. Rather like the Clarkson-Focus RS incident..It stuck with people, and now they are scared of getting a car with a Quaife LSD.

There was a video not long ago, where a guy i know was filming me from his 166 3.0. Apart from my 156 obviosly being quicker then the larger 166, it also shows how well the diff and suspension helps the car negotiate corners much tighter. Perhaps this type of proof is a better way forward then our very theoretial situations.

Will try to see if i can dig up that video somewhere.

Originally Posted by Peter K

Meanwhile i hope you TB, can get a chance to try out bmoferrall's car..?

Good idea. I'd be more than happy to leave my car in TB's capable hands. No doubt he'd be able to flesh out my "It's much better around corners" conclusion with a bit of substance!

To complicate (or simplify ) matters further, I would expect the still operational electronic ASR to do this for you.....

Originally Posted by Peter K

....
All this talk of how the different types work can be very theoretical. F.ex i was not aware that using left foot braking would engange the Quaife ATB to a higher degree ...

Originally Posted by jwq

To complicate (or simplify ) matters further, I would expect the still operational electronic ASR to do this for you.....

Interesting point!

I know the 147 GTA has ASR. Does the GT 3.2 have it too? (The 156 GTA does not have ASR)

I think it depends on the country (i.e. the importer). Here in The Netherlands ASR is (was) standard on all the GTAs (147, 156 and 156SW) Also standard on all models of the GT...
http://local.alfaromeo.nl/pdf/Alfa_GT_TI.pdf

Originally Posted by Peter K

Interesting point!

I know the 147 GTA has ASR. Does the GT 3.2 have it too? (The 156 GTA does not have ASR)

I think that would be a misprint. The 156 GTA never came with ASR. Other 156 models got as standard at one point, but never the GTA.