Audi A4 RWD ?

dnme

Looking at a few reviews of cars recently and I came across one where the reviewer seemed to suggest that the Audi Quattro was a rear wheel drive. It is my understanding that the Quattro is 4WD or AWD (Is there any difference between 4WD and AWD?).

Just got me thinking
Is the Quattro RWD or 4WD
If 4WD, what is the thinking? Why would you need a 4WD car ? I imagine it would not have the same sort of usage as a typical jeep? You wouldn't be using it for off roading etc or would you?

lomb

Quattro depending on the Audi is biased to FWD strongly, is FWD only during cruise but while accelerating and cornering is Four Wheel Drive .

The advantage is far better road holding in wet conditions, around curves, no wheel spin on acceleration allowing full power to be put down. You can feel the 4wd working on rapid cornering.

It allows faster entry and exit speeds to corners than either FWD or RWD.

Disadvantages are frictional and weight losses-increased co2 emissions as well as cost which is why very few modern Audis are fitted with it.
Other disadvantages are purists dont like it as you cant get the tail out and balance it like RWD hooligans. Although it is an inefficient way of getting around a bend it is good fun so quattro is seen as a bit clinical.

disco1

All Audi Quattro cars have 4 wheel drive....

dnme wrote: »

Looking at a few reviews of cars recently and I came across one where the reviewer seemed to suggest that the Audi Quattro was a rear wheel drive. It is my understanding that the Quattro is 4WD or AWD (Is there any difference between 4WD and AWD?).

Just got me thinking
Is the Quattro RWD or 4WD
If 4WD, what is the thinking? Why would you need a 4WD car ? I imagine it would not have the same sort of usage as a typical jeep? You wouldn't be using it for off roading etc or would you?

Chris_Heilong

Quattro sounds like the spanish word for 4.

CiniO

Chris_Heilong wrote: »

Quattro sounds like the spanish word for 4.

I think you meant Italian.

dnme

Many thanks for the replies. So is there a RWD version of the A4? If so what's it called ?

dmc17

dnme wrote: »

Many thanks for the replies. So is there a RWD version of the A4? If so what's it called ?

No. Front wheel or 4 wheel only

Chris_Heilong

dnme wrote: »

Many thanks for the replies. So is there a RWD version of the A4? If so what's it called ?

There is, its called a 3 series BMW.:pac:

Popoutman

The Quattro system in the Audis is 50:50 biased at neutral in the B5/B6 variants. This means that it'll understeer, same as any neutral biased 4WD car. Simple based on the physics. This was one of the handling characteristics of the B5 RS4, it was very difficult to get the tail to step out without really unsettling the car. The Torsen diffs will effectively push more torque as needed to the wheelset with grip.

The B8 A4 is 60:40 at neutral, but can again push more to either the front or the back as needed.

No RWD Audis in a very long time..

Matt Simis

lomb wrote: »

Quattro depending on the Audi is biased to FWD strongly, is FWD only during cruise but while accelerating and cornering is Four Wheel Drive .

The advantage is far better road holding in wet conditions, around curves, no wheel spin on acceleration allowing full power to be put down. You can feel the 4wd working on rapid cornering.

It allows faster entry and exit speeds to corners than either FWD or RWD.

Disadvantages are frictional and weight losses-increased co2 emissions as well as cost which is why very few modern Audis are fitted with it.
Other disadvantages are purists dont like it as you cant get the tail out and balance it like RWD hooligans. Although it is an inefficient way of getting around a bend it is good fun so quattro is seen as a bit clinical.

What you are describing above is the Haldex variant of Quattro, which is a electronic (as opposed mechanical) drivetrain system designed for the smaller or lower power cars (usually). A purist would not consider Haldex a true quattro system, given quattro is usually referred to as "quattro permanent four-wheel drive". Quattro historically (and continues to be in most applications) is a Torsen (Torque Sensing) or more accurately a Gleeson differential worm-drive gear system.

I'm fairly sure no A4 (or bigger) used Haldex, they all use permanent Torsen quattro, which was originally around 50:50 split with later versions providing more rear bias. But the key difference being "proper" quattro is not FWD when cruising then 4WD when needs to be, its always 4WD.
Your disadvantages dont really apply to Haldex, only proper quattro.

Popoutman wrote: »

The B8 A4 is 60:40 at neutral, but can again push more to either the front or the back as needed.

Your split is wrong way around, they made quattro more Rear biased, not more Front biased! Its 40:60 on the B8 and a somewhat different measurement but more Rear split on the Quattro VI gen RS5:

quattro generation VI[edit]
Audi debuted the 6th generation of quattro in the 2010 RS5. The key change in generation VI is the replacement of the Torsen Type "C" centre differential with an Audi-developed "Crown Gear" differential. With the new "Crown Gear" center differential, up to 70% of the torque can be applied to the front wheels while up to 85% can be applied to the rear wheels if necessary.

Incidentally you can get an aftermarket gearing set for the B5 S4/RS4 which will allow upto 88% to the rear (or front) to make them less clinical but still with that 4WD controllablity:
http://www.stasisengineering.com/products/differential-systems

Popoutman

Matt Simis wrote: »

Your split is wrong way around, they made quattro more Rear biased, not more Front biased! Its 40:60 on the B8

My apologies! I should have been clearer about the direction of the split I did mean 40 front : 60 rear at neutral.

lomb

Matt Simis wrote: »

What you are describing above is the Haldex variant of Quattro, which is a electronic (as opposed mechanical) drivetrain system designed for the smaller or lower power cars (usually). A purist would not consider Haldex a true quattro system, given quattro is usually referred to as "quattro permanent four-wheel drive". Quattro historically (and continues to be in most applications) is a Torsen (Torque Sensing) or more accurately a Gleeson differential worm-drive gear system.

I'm fairly sure no A4 (or bigger) used Haldex, they all use permanent Torsen quattro, which was originally around 50:50 split with later versions providing more rear bias. But the key difference being "proper" quattro is not FWD when cruising then 4WD when needs to be, its always 4WD.
Your disadvantages dont really apply to Haldex, only proper quattro.


Your split is wrong way around, they made quattro more Rear biased, not more Front biased! Its 40:60 on the B8 and a somewhat different measurement but more Rear split on the Quattro VI gen RS5:



Incidentally you can get an aftermarket gearing set for the B5 S4/RS4 which will allow upto 88% to the rear (or front) to make them less clinical but still with that 4WD controllablity:
http://www.stasisengineering.com/products/differential-systems

The MK1 TT was haldex, Im not sure about the current gen. It is an unusual system in that the quattro disengages when the esp traction control system is in operation. Whats the point in that? However the technology works in the real world so I wont question it.
Ive never really had any interest in Audis Saloons therefore what purists think doesnt really affect me.
I do know that the R8 is set up to allow the cars back end to break loose and be balanced with a rear bias but that is an exotic limited market product.

Theanswers

lomb wrote: »

Quattro depending on the Audi is biased to FWD strongly, is FWD only during cruise but while accelerating and cornering is Four Wheel Drive .

The advantage is far better road holding in wet conditions, around curves, no wheel spin on acceleration allowing full power to be put down. You can feel the 4wd working on rapid cornering.

It allows faster entry and exit speeds to corners than either FWD or RWD.

Disadvantages are frictional and weight losses-increased co2 emissions as well as cost which is why very few modern Audis are fitted with it.
Other disadvantages are purists dont like it as you cant get the tail out and balance it like RWD hooligans. Although it is an inefficient way of getting around a bend it is good fun so quattro is seen as a bit clinical.

Only In Ireland, I'm sure plenty abroad are fitted with proper engines/ 4x4.

Here sure 2.0 is a rocket ship.
Any bigger and you personally have killed the planet.
FFS

Matt Simis

lomb wrote: »

I do know that the R8 is set up to allow the cars back end to break loose and be balanced with a rear bias but that is an exotic limited market product.

Seems its using the 4:1 gearset like the old aftermarket mod for the S4/RS4:
http://www.audiusa.com/models/audi-r8#quattro%C2%AE

tossy

The R8 uses a Viscous Coupling set up. I've owned 2 haldex cars and one quattro car the real world differences between both are negligible - on a track you might be able to bring out the differences, but in rain/heavy snow etc there was no differnce.

Haldex being FWD most of the time is also a myth usually spun out by quattro nerds On my 2 haldex cars the rear tyres wore faster than the fronts. There was a member on Vortex (i think) years ago who did a great test on the readings from the pressure pump in the haldex clutch the upshot of it was as soon as throttle was applied the pump went live and was on more times than it was off.

_Kaiser_

OK I'm curious now... what's the split in my 2005 3.0 TDI Quattro A6 (C6) then? Is it a "proper" Quattro?

Matt Simis

Kaiser2000 wrote: »

OK I'm curious now... what's the split in my 2005 3.0 TDI Quattro A6 (C6) then? Is it a "proper" Quattro?

Afaik every bigger Audi (bar the Q7) uses the traditional TorSen mechanical centre diff. Its too big and heavy to fit the smaller cars, but on the cars it fits, its an easy superior choice as its near indestructible (its a gear based system, no plates to wear, pumps to leak, electronic sensors to fail etc) while offering permanent 4WD with instant torque shifting.

The latest A6 also offers the sports rear diff too, as introduced on the B8 (I think) S4.