Retrofitting a Q2 to an existing Alfa

You definitely don't need to brake with the clutch in with a Q2 LSD or any LSD I have used with a GTA (Quaife, Autodelta, Madeno as well as Q2)

That said some LSDs have more impact on braking differentiation than others.
e.g.

- A 1 way LSD has no effect under braking.

- A 1.5 way LSD has some mild differentiation effect under braking

- A 2 way LSD has a large differentiating effect under braking, which I have read could cause understeer. This would rarely be used on a performance FWD car, or possibly any performance car. I suppose it is possible that putting the clutch in for something like this could help but you would lose natural engine braking.

I believe the Q2 diff has some effect under braking, I know the EBD/ABS/VDC was recalibrated slightly to match on the Q2 models.

I can't imagine why ABS would not work as well with a diff, since the ABS system works off the wheel speed sensors and has no idea of the level of locking of the diff.
If a wheel is locked under braking, it will release it. It is my understanding with 1.5 way diffs it is possible that they might have help the wheel unlock by somehow transferring a bit of braking torque.

I certainly have had no problems with using ABS on my Q2 torsen diff or Autodelta clutch type diffs.

Adie from AHMotorsport mentioned that the clutch-type diff varaints they and Autodelta use can be set up with various degrees of braking ramp interaction to finely control the effect under braking into a corner. I don't know to what extent this is used by the default AD setup.

I have a slight suspicion I can't brake as well into a corner with my Q2 diff as the Ad diff, but I will confirm wether that is the case next week when I get to try on a familair track with supporting telemetry data. Heres hoping for dry weather, its the wettest June on record in Ireland!!

Cheers,
TB

Originally Posted by henk

does anyone have an idea how an LSD cooperates with ABS brakes?
When braking with an open diff, right wheel on the wet, left wheel on a dry road surface the ABS will interact more frequently on the right side. ABS works in an optimal way since it can affect all wheels independently.
When braking with a locked diff (different road surface again) my understanding is that the wheel on the wet side will not block as soon as it would with an open diff and thus ABS will not react in an optimal way!?

I read somewhere that you always need to press the clutch when braking with an LSD mounted. If this is the case, then it probably is not a good idea to implant an LSD in a Selespeed!?

Henk

Thanks, TB!
Has anyone mounted the Q2 in a Selespeed GTA?

Henk

In my opinion I think that the Q2 helps braking and the car proves to be more stable when braking hard.

The ABS kicks in very rare cases...keep in mind that my tires are due for change so I think that even better results are to be expected from the Q2.

My bella has Koni-FSD and powerflex all around so that might help as well.

Yes it would be more stable if my theory is correct, however my speculation (and thats all it is at this point) is that perhaps it wouldn't want to turn in as keenly under braking (i.e. trailbraking).

Its still very good though, don't get me wrong.

Cheers,
TB

Originally Posted by kgb

In my opinion I think that the Q2 helps braking and the car proves to be more stable when braking hard.

I don't know about Q2 in a Selespeed, but I am sure Autodelta have fitted their LSD's to mnay GTA selespeeds, including 3.7L ones.
Can't imagine a problem with the selespeed though since it is a roboticised manual.

If the Q2 fits a manual GTA it will fit a GTA Selespeed too. Same diff.

so , it is a few months , and no info about fitting LSD to 2.0 JTS 5 speed gearboxes?

it's not a question about Q2 , but generally the LSD system

is it ANY way to fit a LSD to a 5 speed GT 2.0 ??

Just had Q2 fitted to my 2001 GTV V6 3.0 6-speed. All good so car after 60 miles of dry and then wet motorway and 30 miles drenched fast A-roads.

Originally Posted by tribaldancer

so , it is a few months , and no info about fitting LSD to 2.0 JTS 5 speed gearboxes?

it's not a question about Q2 , but generally the LSD system

is it ANY way to fit a LSD to a 5 speed GT 2.0 ??

The Q2 won't fit, but any LSD designed for that gearbox will fit. There are several available all costing at least double the Q2 price.

Q2 is a one way LSD, so no problems under braking.

Originally Posted by Lionheart

Q2 is a one way LSD, so no problems under braking.

Does that imply that you will have braking problems with a 2-way LSD?
What exactly is the effect on braking? Are the assumptions that I made above correct (for a 2-way LSD)?

Appreciate your help!

This video would seem to indicate that its a 1.5 way LSD though?
(at about 2min 10s)

i.e. when Philippe Krief (Alfa Technical Supremo) explains how it works under decelleration to reduce the risk of oversteer by keeping the torque split in favour of the external wheel.
A 1 way diff would act as an open diff under decelleration.

AFAIK Any diff that contributes to torque control between wheels under decelleration can't be classed as a 1 way diff.
Its obviously not a 2 way diff which would normally be used for drifting RWD cars, and would tend to cause pronnounced understeer under braking while engaged for a FWD car.

http://www.motorauthority.com/news/t...eos-q2-system/

Cheers,
TB

Originally Posted by Lionheart

Q2 is a one way LSD, so no problems under braking.

Originally Posted by David C

The Q2 won't fit, but any LSD designed for that gearbox will fit. There are several available all costing at least double the Q2 price.

could u give me a few websites for these lsd s supporting 5 speed transmissions

and will these diff s give the same feeling and functions as q2 ?

Gripper (a more track oriented diff)

Also see: AH Motorsports.co.uk

Originally Posted by Lionheart

Q2 is a one way LSD, so no problems under braking.

The Q2 is not a LSD.

Originally Posted by Caldo Bollente

The Q2 is not a LSD.

Most would call it a torque biasing LSD

1, 1.5, 2 way are how the ramps in a LSD are set up, the Q2 doesn't have these therefor pointless describing it as such as it doesn't work in the same way (excuse the pun).

Its might be the case that the term "1.5 way" is really only used to describe clutch type diffs (not sure), however the principle of whether a diff works under decelleration is a generic one - that applies to torsen diffs and clutch type diffs.

For a torsen diff you have can have seperate torque bias ratios for both acceleration, and for coast mode (i.e. decelleration caused by engine braking).
Obviously Alfa have chosen to make use of some differential action under engine braking for stability reasons.

More detail as ever, from this paper.
http://zhome.com/ZCMnL/tech/Torsen/Torsen.htm

Cheers,
TB

Originally Posted by Caldo Bollente

1, 1.5, 2 way are how the ramps in a LSD are set up, the Q2 doesn't have these therefor pointless describing it as such as it doesn't work in the same way (excuse the pun).

Thanks for the useful information Trailbraker

Ps: I reinstalled the FMIC on my JTD today, after some cleaning....compared with the original side intercooler, now the car spins in 2nd gear again, but now with the Q2. The temperature drop is Huge!!! Today it was 40*C over here.

Soon I am planing to visit a Dyno stend...as I am wondering how much torque I have now.

If anything the Q2 would be a two way in that it has a constant TBR, the difference being compared to a LSD there is no certain point of lock, instead it works continuously, adjusting itself instantly to what's going on at the wheels.

The white paper you linked is for the T1 which does indeed appear to change TBR according to thrust by way of movement in the side gears. If you compare it to a diagram of the T2 that looks very much fixed.

http://www.torsen.com/products/T-2.htm

Originally Posted by Trailbraker

Its might be the case that the term "1.5 way" is really only used to describe clutch type diffs (not sure), however the principle of whether a diff works under decelleration is a generic one - that applies to torsen diffs and clutch type diffs.

For a torsen diff you have can have seperate torque bias ratios for both acceleration, and for coast mode (i.e. decelleration caused by engine braking).
Obviously Alfa have chosen to make use of some differential action under engine braking for stability reasons.

More detail as ever, from this paper.
http://zhome.com/ZCMnL/tech/Torsen/Torsen.htm

Cheers,
TB