Brera/159 Q4 system - Alfa Romeo Forum
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Brera/159 Q4 system


do any of you have - or can point me in the direction of - any material that relates to Alfa's Q4 system as used on the Brera or 159? Technical diagrams would be cool (not that I'll understand them lol), but I don't yet know even the basics of the system:

- is it a permanent 4x4 (my gut feel is that it is)
- i don't know what the power split is between the front and rear of the car
- does the set up affect the location or the size of the fuel tank
- is this Alfa's own system, or co-developed? And how does it compete with say the Quattro system (i.e. better, worse, cruder, more sophisticated etc). I don't mind whether it is better or worse, but I'm trying to get some context.
- is the set up exactly the same in the 159 and Brera (I guess the prop-shaft is shorter on the Brera?)

I know this all sounds a bit anal but I like to know a little of a car's set up when I own it, so any help would be appreciated. Diagrams or vids would be most excellent.

Thank you gang,


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Re: Brera/159 Q4 system

Hi g

It's a proper, permanent, three diff setup. None of that nonesense VW use where it's front wheel drive until it needs to be all wheel drive.

I've copied and pasted this:

"The ‘Alfa Q4’ system

The Alfa 159 also adopts an evolved version of the permanent 4x4 system with three differentials (with a Torsen C self-locking unit at the centre). The heart of this design is the ‘Alfa Romeo Q4 four-wheel drive’ system, which splits torque constantly and dynamically between the four wheels, reaching the highest levels of active safety and sportiness. The Torsen C self-locking differential sends drive torque 57% to the rear wheels and 43% to the front. The system also guarantees excellent traction in all grip conditions by automatically checking any slipping.

The torque split between the front and rear axles is modulated constantly by the Torsen C central differential on the basis of grip.

This feature harnesses sportiness to enhance active safety. Modulation is mechanical, continuous and gradual, to enhance the perception of optimal, enjoyable, easy driving. There are no gaps in the torque delivery. Where grip is concerned, the behaviour adapts gradually and smoothly to changing road conditions. This ‘mechanical’ control is backed up by electronic stability control, which boosts performance and safety margins, in line with the Alfa Romeo philosophy.

The car is the state of the art in technical terms and offers important advantages:

• Q4 permanent four-wheel drive with a Torsen C self-locking differential makes for better roadholding, entertaining driving and smooth responses. Other technological archetypes with electronically controlled joints do not achieve the optimal balance between understeer and oversteer or the smoothness that are innate in the Alfa 159, and translate into superb active safety.

• The torque split in favour of the rear axle makes driving even more entertaining, because the car is even easier to handle, without detracting in any way from stability during sudden lane changes on the motorway, or other emergency manoeuvres.

• The possibility of travelling safely when grip is poor without having to use electronics to split torque, enhancing the enjoyment of driving.

We could say that the Alfa 159 Sportwagon Q4 interprets four-wheel drive from the Alfa Romeo point of view: it is basically a ‘mechanical’ system enhanced by cutting-edge electronic technology to guarantee maximum comfort and entertainment, combined with superb performance and absolute safety."

I've also found that it can split the power between (72/28) and (22/78) front/rear.

Sounds good stuff!

Remember the V6 is now available in front wheel drive only, so remember to ask for Q4 on the order form!
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Re: Brera/159 Q4 system

Hi Scudetto,

Torsen is the company who hold the Torsen diff design that Alfa and Audi use.

The Q4 diff setup is the same as the top Audi RS line use.
It cant really be compared to the part-time Haldex 4WD system used further down the VW range.

The Q4 uses a permanent 4WD sophisticated Torsen type-C "twin-diff" setup that houses the front and centre diffs together - apparently this lets them work together better.

Torsen T-3 Differential

So the car will have zero traction issues
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Re: Brera/159 Q4 system

Are you getting one, G?
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Re: Brera/159 Q4 system

Not sure at present the value of the Q4 versus the extra weight as it is not easy to play sporty with the 159. Besides the pure weight and size of the car the seats are not really snug enough.

I had no choice as I purchased off-spec on the special Fiat lease deal last yearc on the 3.2 but would not bother with the Q4 again if I had a choice.

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