Has the Brera S got the Q2 slip-diff??

Hi guys,
Some threads on here suggest that the Brera S has got the limited slip diff? Anyone know anymore about this?

John

I'm sure it is described as "Electronic Q2", which probably just means better traction control, not an electronically controlled LSD.

Yes, its just a new version of the ASR stuff rebranded as "Q2 electronic differential".
Given the modest power to weight though, its not the end of the world it doesn't have a real LSD, although it would have been very nice indeed for very sporty driving.

I would be very interested to know if anyone has driven 2007 and 2008 cars back-to-back to assess the value of the latest electronic differential.
I have read a number of contributions to the forum regarding the system and although I am certainly not defending its introduction in place of the Torsen mechanical Q2 differential, there seems to be a fundamental misunderstanding of its function.

In a 2007 car, when accelerating out of a corner it is conceivable that the torque would result in the unloaded inside wheel, spinning up with excess power. Under this circumstance, the ASR/traction control system would cut in, reducing engine power to the point where the spinning stops.

In the 2008 chassis, the sensing system instead responds by applying a braking force to the spinning inside wheel. The engine continues to produce the same torque - ie there is no engine management taking place. Instead, as anyone who has ever played with a differential setup on an RC car or a Meccano set would realise, when one wheel is restrained all the torque is transferred mechanically to the other (in this case the outside) wheel. In other words a proportion of the engine torque is transferred to the wheel with the most grip, thus replicating to a degree, the effect of a mechanical limited slip diff. As it is not intended to merely cut the engine power to regain traction, it should have a positive effect on cornering.

If it is done correctly, and the jury is still out on the Alfa system, there will be an increase in traction. A similar but undoubtedly more sophisticated system is fitted to road going Ferraris as the E-Diff, albeit a rear drive system.

There is an explanation of this on the Alfa site somewhere.

Seems a shame that they couldn't use the mechanical Q2, maybe they are saving it for the MY2009 models with the new engines? In the meantime electronics will have to do.

One interesting thought is how much extra wear it's going to put on the brake pads/disks...

Simes.

New e-Q2 didn't seem much cop when I test drove the S, particularly poor on broken surfaces where my old Q2'd GT would have coped no problem, Brera just cut the power ultimately still enjoyed the drive though.

Hi Mike,

the 2007 cars had ASR, but it had very similar traction control to what the Marketing men have now decided to label as "Electronic Q2".

ASR had two stages.

1) as you describe, cut the power when you are applying way too much power.

2) When just one wheel is spinning , apply the brake to that individual wheel. Practically all modern traction control systems do this.

So whats the difference with electronic Q2 as compared to ASR?
Mainly marketing I suspect, plus some improvements based on refinement over time I'm sure.

The "old ASR" was useful for "normal" driving on roads when you weren't pushing on particulary (which would be 99% of the time).
On track though you really just had to turn it off since it

a) Was only partially effective in restraining unloaded wheelspin,
once you had over a certain amount it resorted to backing off the throttle anyway - since it could tell it would just be cooking the brakes.

b) ..was quite slow in returning the power to match the available grip while cornering compared to a vaguely keen driver, especially if any transient bumps were encountered - which didn't actually really require the throttle being backed off severely.

c) ASR also didn't do much for the brakes since it was reducing the amount of cooling time they had available between corners.
In the wet it was just plain useless for track use, you came to a standstill (relative to other cars) when you hit a modest puddle.

Cheers,
TB

Originally Posted by ukmike2008

I have read a number of contributions to the forum regarding the system and although I am certainly not defending its introduction in place of the Torsen mechanical Q2 differential, there seems to be a fundamental misunderstanding of its function.

In a 2007 car, when accelerating out of a corner it is conceivable that the torque would result in the unloaded inside wheel, spinning up with excess power. Under this circumstance, the ASR/traction control system would cut in, reducing engine power to the point where the spinning stops.

In the 2008 chassis, the sensing system instead responds by applying a braking force to the spinning inside wheel. The engine continues to produce the same torque - ie there is no engine management taking place. Instead, as anyone who has ever played with a differential setup on an RC car or a Meccano set would realise, when one wheel is restrained all the torque is transferred mechanically to the other (in this case the outside) wheel. In other words a proportion of the engine torque is transferred to the wheel with the most grip, thus replicating to a degree, the effect of a mechanical limited slip diff. As it is not intended to merely cut the engine power to regain traction, it should have a positive effect on cornering.

If it is done correctly, and the jury is still out on the Alfa system, there will be an increase in traction. A similar but undoubtedly more sophisticated system is fitted to road going Ferraris as the E-Diff, albeit a rear drive system.

There is an explanation of this on the Alfa site somewhere.

Seems a shame that they couldn't use the mechanical Q2, maybe they are saving it for the MY2009 models with the new engines? In the meantime electronics will have to do.

BTW the Ferrari E-Diff is more than just a software upgrade.
It has major mechanical and electronic components, and is pretty high tech stuff

-a high-pressure hydraulic system.

- a control system consisting of valve, sensors and electronic control unit;

- a additonal mechanical unit housed in the gearbox.

Torque is continuously distributed between the wheels via two sets of friction discs (one for each driveshaft) controlled by a hydraulic actuator. The amount of torque actually transmitted to the driven wheels depends on driving conditions (accelerator pedal angle, steering angle, yaw acceleration, individual wheel rotation speed) and brings considerable advantages in terms of performance, direction stability, active safety and handling feedback.

Was that the 3.2 or the 2.2 Sandy?

You can still turn it off presumably?

Originally Posted by sandys

New e-Q2 didn't seem much cop when I test drove the S, particularly poor on broken surfaces where my old Q2'd GT would have coped no problem, Brera just cut the power ultimately still enjoyed the drive though.

Originally Posted by Trailbraker

BTW the Ferrari E-Diff is more than just a software upgrade.
It has major mechanical and electronic components, and is pretty high tech stuff

Yes I realised that TB - as you might expect considering the pedigree and the price.

Thanks for the input on the 2007 system

Originally Posted by Trailbraker

Was that the 3.2 or the 2.2 Sandy?

You can still turn it off presumably?

I believe its one press to kill the traction control only - press and hold down to kill the Vehicle stability control - accompanied by warnings of imminent death on the display lol

Originally Posted by Trailbraker

Was that the 3.2 or the 2.2 Sandy?

You can still turn it off presumably?

Only the 2.2 so the car wasn't even that lairy, but the sort of roads I travel on loss of traction is quite easy due to bumps and broken tarmac, didn't think to try and turn it off.

I've not activated the ASR / VDC etc in 9.5k miles in my 2.2 Ti. The S has the same tyres so I doubt you'll lose traction unless the road is ultra wet & greasy and you have a lead right foot.

nice sunny day and the tyres were sufficiently warm, Just planted it heavy out of a bend like I would do in my GT because I could get away with it, I couldn't do it with the 2.2 even with its meagre resources, sure a more balanced approach and I'm sure you could take it beautifully with the S but as a comparison to a car with a proper diff which is what i was doing its not as good and would ultimately be slower.

Originally Posted by Simes

One interesting thought is how much extra wear it's going to put on the brake pads/disks...

Simes.

There was a test in Evo of a car with a similar electronic setup and they commented on the extra brake dust suggesting the system had been working hard.