Retrofitting a Q2 to an existing Alfa

Thanks for your update. probably best (they know that I will collect and pay for the parts: they are my Alfa shop for > 18 years now)
(and yes: I know I'm an old man )

I have a friend of mine who has some connections with Alfa dealers in Italy, he will be back in Italy in 2 weeks...I will be using him to get the Q2...if he is quick...I might ask him to do a favour for all of us and send the Q2 from Italy to who ever wants it...off course if he is willing to do that.

AHMotorsports are selling Q2 diffs for £220.00 plus vat.

They do not ship outside UK or even respond to emails.

I dealt with Adie entirely by email, never spoke to him until I handed him the keys to do the diff on my car so he does respond, probably just busy.

Can't fault the service he gave me, he advised me against his other LSD kit based on what I said I was after and he suggested I look for a torsen diff without pushing other stuff, he had no problems fitting the Q2 to my car, most other garages I spoke to wouldn't touch the job or quoted double the price for the work.

Maybe he doesn't bother to respond to emails from other countries at all. I had sent him an email once and never got a reply. Oh well...

Same thing here (last year, no response what so ever ...). Pity, as they have nice stuff on their website !

After changing the diff and the 2 bearings, how do you guys determine what spacer/ring size to use, or do you just use the ring that was allready in use with the OEM diff/bearings.
There is this special alfa tool to measure the thickness (ring) to use for the diff preload.

Do you mean ring gear, aka crown wheel?

You use the existing ring gear and bolts. You can also use the existing bearings, provided that they are in good shape (low mileage) and you don't damage them upon extraction from the free diff, which needs patience.

Tip: If you have a V6 with a 56-tooth ring gear you can use a 57-tooth one from a JTD if you want to shorten all ratios a bit. No need to change the pinion gear from what i've been told. But IMO it may not be worth the extra cost, the JTD ring gear costs about £100.

Hi Sandy

AHM can also supply plate type lsds for the 5 speed box ie 2.0 ts

and preload must be set on the diff bearings

TB LSDs will not work as well as a plate type in snow or ice or when a
wheel is in the air with a plate type you can drive very slowly with a broken drive shaft thats why they are used more in racing plus they
can be set with braking ramps to link both wheels under braking aswell
but like ive said for road can be noisy and they wear very slowly but
they do

Originally Posted by adie

TB LSDs will not work as well as a plate type in snow or ice or when a
wheel is in the air with a plate type you can drive very slowly with a broken drive shaft thats why they are used more in racing plus they
can be set with braking ramps to link both wheels under braking aswell
but like ive said for road can be noisy and they wear very slowly but
they do

Unfortunately I have to say this is not true at all. With a broken shaft and using a Quaife LSD you can still drive. Also, a plate diff is not even near as precise as a torsen type diff when driving (read: cornering). Also, with a torsen diff you keep more traction then with a plate type, as it does not have a fixed limited slip. An other advantage: it does not need all the maintenenace a plate diff needs.
(have driven many road and race cars with plate LSD and torsen LSD; front, 4 and rear wheel driven. Plate diff's don't match...)

The braking: better to use a racing ABS then locking the drive shaft's as you mention.

Hi
Ok sorry i dont agree as abs will only limit the locking of a wheel
not help give you more grip thats why btcc wtcc etc all still use
plate type lsds dont forget plate type lsds can be set up in many
ways and most are set with to much preload and to much grip
ie using to many plate surfaces so depends on what you drove
I used the TB type in race cars as well its the best to drive with
best all rounder but in the wet useless and kerb hopping they
loose drive the plate type dose give a faster lap time and better
under braking in racing any way.

So for fast road i think TB is the best no nosie no ajustment
fit and forget
fast road track day TB or plate
Race plate type

Also slip is not fixed depends on the ramp angles used
as the pins go up the ramps the more the lock plus
this is only limited by the amount of plates used
a plate type lsd set up wrong is really bad to drive
ive raced fwd for years and ive found plate to be faster
in a lap when set up correctly

True: you can set the fixation with plate type, and yes: that works very very nice for WTCC/BTCC, BUT: do you want to take you're diff out for every other week-end you go driving ? Unless you've got the budget (and the personnel) to do so (changing diff all the time), Torsen type is the way to go. (in racing you have to adjust to any circuit anyway (gear ratio's etc) therefore it is not very difficult to change the LSD setting/plates)

Also: driving with a plate diff is more difficult then with a torsen;

I recently had the chance to drive a modified 156 GTA with an Intrax nitrogen-type coilover suspension, 18" alloys and a Q2 and I must say i was impressed. The ride included turns of different radii, from 4th gear open curves to 2nd gear near-hairpins with mostly damp slippery surface.

Yoy can feel the Q2 "engage" by the reduction in the steering wheel's kickback (not sure about the english term here, "torque steer" maybe?) which can be from very subtle in 3rd gear turns to quite evident in hairpins. I am accustomed to this type of steering wheel feedback because my Sud has it although it does not have an LSD. However, the steering wheel does not squirm or try to turn by itself, so it does not surprise the driver, only informs him that the diff has just kicked in. The car's cornering radius does not change at the point of engagement, meaning that you do not get traces of initial understeer and then evident nose tuck-in, instead you have a smooth line throughout the turn.

I managed to make both front wheels spin during a 2nd gear turn with high rpms and the car understeered very gently. To correct the understeer i lifted off the accelerator, as i would do with any other FWD and the car tucked in without any traces of rear-end destabilisation. Therefore understeer and its correction is not different that in a car with a free diff, the only difference is that the steering wheel does not inform you much of the wheelspin; you have to tell by the increase in rpm and the nose going -slightly- wide, but the car gives you ample time to react.

Acceleration has improved as well. It is very difficult to spin the wheels at takeoff, even on slippery surfaces. That will make street racers happy but disappoint people that fancy traffic light burnouts, because you simply cannot do that anymore.

One might argue that i cannot be sure what part of my experience can be attributed to the Q2 and what part to the Intrax suspension, but i must say that the suspension was adjusted for road use and was not firmer than my Koni/Eibach combination.

Other than that, i must say that i envied the guy's GTA, which can now put all of its 300HP and 35Nm (according to the owner) on the road. In comparison to a 4WD Leon 20VT i've driven under similar circumstances i must say that the Q2 GTA has similar cornering abilities on slippery surfaces while being more informative, agile and fun to drive, certainly much more of a driver's car.

Hi AB156V6 I have to disagree with some points to an extent

I have no race experience but have done many track days in my road car with essentially the same type of clutch type diff Adie is talking about.
I also have had a chance to do a head to head comparison with a quaiffe diffed GTA (posted a thread with videos and telemetry a while back) so as an amateur I have a pretty good idea of the practical differences of these diffs as applied to a GTA.

My clutch-type diffed car is a doddle to drive on or off the track, with almost zero torque steer, btw torque steer is hugely reduced from standard
My wife can drive the car without noticing anything funny.
I don't need to twiddle with the diffs settings, but its nice to have the option if the diff was being serviced.
The people who sold me the diff just discussed what type of driving I would do and chose a setting for me - no technical knowledge was actually required on my part. My local mechanic would just need to install the diff as configured by the retailer who would have configured all the diffs internals appropriately.

I don't believe modern lsds have a fixed limited slip under all load conditions, I can clearly feel the gradually increasing lock as I apply smoothly power on corner exit. I suspect you are referring to the intial torque transfer?
As I undertand it the torque transfer then increases based on load determined by the difference in rotational velocity of the wheels up to a higher determined torque transfer setting.
Seems to work pretty well to me - I don't experience any tugging at the wheel and I have a lot more torque than standard.

Now if you did something silly like applied a lot of lock on a trailing throttle and then stamped on the gas while in the powerband you would feel sudden torque steer for sure - but you typically would never do this..

Ignoring long-term diff maintenance for the moment:
For day use I personally have found no real drawbacks, and for fast road use its hugely more precise on the road than the standard diff and much much *easier* to drive under full throttle on a bumpy road with.
In a head to head track test I did (I posted a thread with telemetry and video a while back) the clutch type diff appeared to be to significantly outperform the Quaife diff for track driving, at least as applied to the Quaiffe 2.5 v6 diff installed in a GTA.
Its true that the Quaife is more precise in terms of instant torque adjustment, but the modest torque bias ratio that was specified for the 156 2.5 V6 quaife diff meant that it was much easier to spin the wheels under really hard cornering than the clutch type diff.
Once the GTA's inside wheel became unloaded due to roll, the quaife diff just stopped working and the inside wheel spins up, ..in a situation where I could be on the gas harder much earlier with the clutch type diff.

I'm very happy with it, but yes the Quaife diff would be a fix and forget option and very suitable for road use especially since it is totally unobtrusive and even smoother in operation, mind you the Q2 diff sounds like a bit of a bargain!

BTW Adies price on clutch type diffs is very competitive too!
Especially since you would be dealing with somebody who has race knowledge of how to set them up.

Cheers,
TB

@TB: interesting to see that experiences very. Many people in the rallye arena (like the 325 rally challenge) are changing from plate diff to Quaife, due to more traction (read: accelleration in difficult situations) over a plate diff.
I've had the pleasure of driving, on the same car (mine ), with both plate and Quaife diff experiencing the same thing: more grip with a Quaife diff then a plate diff. (read: faster times on track)

Driving with a plate diff an FWD is less comfortable then with a Torsen type diff.

Problem is: most (race) gearboxes have been set-up for plate diffs in the past; therefore many people still use them (and will (have to) keep using them)
Also less maintenance (like the gripper diff; driven that too) plate diffs are available, but lack the precision of a torsen type (eventhough some people prefer the more brutal way a plate diff works; personal preferences apply here too ).

From a technical stand point the Torsen diff is of a higher level then the (old(er)) plate diff types.

For most Alfa's (with FWD) there are no plate diffs available, but the choice between 2 Torsen type LSD'd: the Q2 from Torden and the ATB from Quaife, which is good news for the FWD Alfa people !

Anyway, let's discuss this over a beer at the Nurburgring during the international AO event

Originally Posted by AB156V6

For most Alfa's (with FWD) there are no plate diffs available, but the choice between 2 Torsen type LSD'd: the Q2 from Torden and the ATB from Quaife, which is good news for the FWD Alfa people !

I believe that the Q2 is so much cheaper than the ATB that only a person who is after doing the best lap times in a racetrack would even consider going for the latter. Or if there are doubts about the Q2's ability to cope with a seriously modified engine (e.g. oversized to 3700cc, supercharged or both) that would get him to go for a maybe custom-made ATB, provided of course that Quaife will offer him the same lifetime warranty they offer for stock V6s.

Oh one thing struck me, the turning circle of the GTAs is so lamentable that I suspect that it actually hides some of the awkwardness associated with clutch type diffs when parking etc - its a feature!
e.g. If the GTAs actually had a tighter turning circle then the Diff preload would be making itself felt a lot more than it does.

Originally Posted by AB156V6

Anyway, let's discuss this over a beer at the Nurburgring during the international AO event

Sure thing

TB

@alfasud TI, i don't mean the ring gear but the single ring(shim) that is positioned behind one of the two driveshaft covers (seal) . The covers on the diff housing together with this certain ring adhust the position of the diff unit.
The thickness of that ring has to be determined according to the alfa workshop manuals to adjust the tension(pre load?) on the diff, special tools are needed to assemble the geabox and diff,
Do you guys determine what size ring to use (available at alfaromeo) or do you just use the old ring.