Retrofitting a Q2 to an existing Alfa

Interesting I wouldn't rule out getting a cheap RS as an expendable track car in a few years at some point, so useful to know.

Originally Posted by David C

There were two versions of the Focus RS diff too after initial complaints. Unfortunately they apparently have the same Ford part number!

This is great ! Much cheeper then the Quaife ATB.
Does anyone know the difference between the settings (lsd percentages) of a Quaife and the Q2 ?

A quick question, is the 8v JTD diff the same as the one in the 16v JTD???

yes

It looks like it will fit any recent V6 or JTD, plus the 2.0TS 166 which use the 6-speed box.

Originally Posted by AB156V6

Does anyone know the difference between the settings (lsd percentages) of a Quaife and the Q2 ?

According to Peter K:

Originally Posted by Peter K

Quaiffe engineers estimate is can shift up to 50%...

On the other hand the Q2 max bias ratio is 4:1. Does this mean that it can go up to 80% momentarily? TB or David, care to comment?

Yes I beleive that 4:1 would mean 80% to one wheel, or in other words a minimum of 20% will be going to one wheel - thats sounds pretty good.

Interesting, I noticed on the Quaife america site that Quaife say that they don't generally detail information about the bias ratio (company secrets no doubt ),

..but then pretty reasonably say that "The angle and tooth form of the helix used, the number of pinions used, and many other factors (including the particular car fitted) all contribute to how the differential behaves and biases drive torque".

Oh just found this interesting link where a Torsen engineer comments on the competitions (i.e. Quaifes diff) after a Quaiffe engineer commented on theirs
(Torsen diff Vs Qauife diff).

http://www.contour.org/archive/showf...3&o=&fpart=all

What is mentioned here is that the diff made by Torsen (at least in this case) seems to support larger torque biases than Quaifes, this is a good thing for sporty driving.
Some interesting comments in the thread..

Probably best to not get too hung up on just a single paramater of the torque sensing diffs, but if the Q2 diff can transfer power more aggressively on cornering while also being as cheap as chips - well that would be great news , especially if it can take decent torque !

If somebody who has fitted one can just take a 2nd gear corner and turn tighly in (late apexing) causing the car too lean heavily and apply throttle and report back what happens - that would be very useful
If no wheels spin or even if both wheels spin, thats good news.
If the inside wheel always spins up first that means that you have reached the limit of the diff.
Of course it will be much harder to spin than with the open diff so you do have to have some decent cornering g's to make the inside wheel unloaded, turning in deliberately late is an easy and safe way to do this.

Cheers,
TB

I seem to find figures around 2:1 TBR.

And also 1 site (in german) with 30% max.

http://de.wikipedia.org/wiki/Sperrdifferenzial

Does this mean 70-30%.
Or 50%+30%=80% to wheel with grip, so 20% to the spinning wheel? I'm confused now?

2:1 would defintely be 67% to 33% split of power, I beleive this is not an untypical deployment for a Quaife diff, in fact the thread I linked to above mentioned the Torsen engineer saying that a 67% / 33% split was the setting for the Quaife diff for the Contour saloon (sort of a US version of the Mondeo).
That car is so soft and woolly that it would need a low torque bias, its not remotely sporting

Originally Posted by guezen

I seem to find figures around 2:1 TBR.

And also 1 site (in german) with 30% max.

http://de.wikipedia.org/wiki/Sperrdifferenzial

Does this mean 70-30%.
Or 50%+30%=80% to wheel with grip, so 20% to the spinning wheel? I'm confused now?

Robert My german sucks so not sure what I am looking at in your link

..but if they were talking about clutch type diffs something like "a 30% locking diff" would be a common term.
In this case I *think* it means that up to a 30% initial transfer will take place to the wheel with more traction (so 50% plus 30% = 80%) resulting in 80% power application to the outside wheel. I think the amount of torque transfered then increases more under increased load as more differential locking is applied..

However the in the case of a cluch type diff the inside wheel can't spin up out of control even if it has no more traction available since the friction in the clutch plates increases with rotational velocity and so it is bound (relatively locked) to the other wheel.
i.e. the clutchtype Diff works "even harder" to control the unloaded wheel.
On the otherhand with a torque sensing diffs once one wheel begins to spin the diffs performance "collapses" to that of an open differential until some traction is regained.
The bigger the torque bias ratio for a Torsen diff the less chance of this collapse happening, but the more likely you are to have some torque steer due to the bigger transfers of torque supported ..but big swing - open diffs cause torque steer anyway!

In general I don't think you can compare locking percentages for Torsen diffs and Clutch type diffs directly though, there are too many other factors to take into account (not many of which I have a clue about )

Prodrive built the Focus RS's (not a lot of people know that). I had a tour there recently where all was explained

The reason that the RS was so "snatchy" to drive was because of the standard McPhearson suspension. The fella from PD said the issue does not happen on cars with double wishbone suspension

Cheers,

Well thats good news for us though

I presume its because Double wishbones are better at putting the power down under hard cornering - I guess there is a good reason that double wishbones are used in Race cars.

Originally Posted by Squadrone Rosso

The reason that the RS was so "snatchy" to drive was because of the standard McPhearson suspension. The fella from PD said the issue does not happen on cars with double wishbone suspension

Cheers,

Take a look at this drawing:



Would somebody try to explain what it tells us?

Originally Posted by Trailbraker

Well thats good news for us though

I presume its because Double wishbones are better at putting the power down under hard cornering - I guess there is a good reason that double wishbones are used in Race cars.

Yep. The wheels stay flat even when cornering

Originally Posted by alfasud.ti

Take a look at this drawing:



Would somebody try to explain what it tells us?

Haven't got a clue.....

Open: = up to 100% power loss (read: grip)
Torsen 2.5 = 40% loss (ie max 60% grip, due to torque biasing to the wheel with grip)
Torsen 5.0 = 20% loss (ie max 80% grip, due to torque biasing to the wheel with grip)

Just do not kow what the 'tractive effort' means.
At reichhard Motorsport (Renault circuit cars) they use plates LSD's with 35 to 45% pre-slip and 70% full load slip. For circuit cars.

(now with lifetime warranty (which is not bad at all): http://www.quaife.co.uk/Alfa-Romeo-1...B-differential )

Originally Posted by David C

yes

It looks like it will fit any recent V6 or JTD, plus the 2.0TS 166 which use the 6-speed box.

Will that include the 156 2.4jtd with 136bhp???

I think it will fit any of the recent 6 speeders, if you have a parts CD you can check which parts are shared between models I think.

It would even fit the Diesel 145/146.

fair enough, I don't have a lcue I thought it had to be a six speed box

I don't know what box was used in those.
But it seams that all the V6 & Diesel 145/146/147/156/166/GT/GTV/Spider use the same diff unit.
Plus the 2.0TS 166 which uses the same 6-speed box as the V6, but with a different bellhousing.

I think I got it.

Its just showing the total amount of traction (y-axis) that can be obtained with one wheel on an infinitely grippy suface and the other wheel on various levels of slippy surface which is represented by the x-axis