How does the quattro work in the s3.

[kazino21]

Hi guys, been looking around and I can't seem to find exactly how the 4wd on the s3 works. There is a nice demo on the audi website which says 50:50 normally (but this may be just for the latest stuff wasn't about s3) but that it changes (obviosly) when the car needs grip in different places. However others say that normally it's 90:10 giving the characteristics of the fwd car which I would have thought it stupid thing to do rwd is obviously loads more fun.

So what's the deal?

Thanks in advance.

 

[god_thats_quick]

It's effectively front wheel drive until wheel slip occurs in the S3 so it's 100% torque to the front wheels under crusing conditions, but can in some situations transmit nearly 100% of torque to the rear.

Have a look at the below should answer some questions you've got. /ubbthreads/images/graemlins/beerchug.gif

http://www.audi-sport.net/ubbthreads/sho...true#Post339279

 

[imported_highlander1]

S3"s arn't proper quattro's in the sense they just use the name to keep it in the family. I think the system is based round the golf 4motion set up.
Cheers,
Deano.
P.S. if i'm wrong then ooopppps.

 

[AL_B]

Follow the links guys and sub-links in the other posts.

All is explained by a guy from Haldex, the company which makes the Haldex 4wd system in the S3 and TT.

AL

 

[god_thats_quick]

[ QUOTE ]
S3"s arn't proper quattro's in the sense they just use the name to keep it in the family. I think the system is based round the golf 4motion set up.
Cheers,
Deano.
P.S. if i'm wrong then ooopppps.

[/ QUOTE ]

It isn't based on, it's the same system in the Golf 4 motion / R32, TT, A3 and many other cars as Al has said if you really want to understand have a look at the link and all the related stuff.

You are right that it's not the same as the 4WD system used in the bigger Audis, but I think they now just use Quattro as a synonym for 4WD.

 

[jojo]

[ QUOTE ]


You are right that it's not the same as the 4WD system used in the bigger Audis, but I think they now just use Quattro as a synonym for 4WD.

[/ QUOTE ]

Isn't this true, it's like saying you have a high end Audi aswell these days, when you say Quattro, people bow before you. /ubbthreads/images/graemlins/lol.gif

 

[kazino21]

Okay read it, very interesting read. Thanks guys.
So what does the upgraded haldex controller do exactly. Looked for one can't find much info on them, just says it is set up more aggressively but doens't go into details like that thread did.

 

[imported_ZeroK66]

[ QUOTE ]
, but can in some situations transmit nearly 100% of torque to the rear.



[/ QUOTE ]

Didnt think this was true?? Thought the most it could do to the rear was 50%? All it is is a clutch... when the clutch is fully engaged 50/50 split occurs... am I wrong?

 

[madvw]

no, it can never do more than 50/50 on haldex, as all you're doing is engaging/disengaging the rears.

 

[god_thats_quick]

READ THE ARTICLE FROM THE GUY FROM HALDEX!!!

In some situations ie 100% wheelslip on the front wheels it can transmit close too 100% of torque to the rear.

 

[madvw]

I'm happy with the description in both these articles, but how would the drive be taken away from the front wheels? Surely the front diff is powered 100% of the time - there's no second haldex here.

I was under the impression that the only haldex there is, is in the transmission to the rear wheels, so power can be transferred if necessary if the fronts are slipping - but there is no mechanism to actually remove the fronts from the power delivery completely?

the point is, is that haldex CAN supply 100% of the AVAILABLE torque to the rears, but Audi dont disengage the fronts, so the torque split is never going to be more than 50/50.

If there was the case where you could, i know i'd be paying good money for a controller where the torque bias was more on the rears, but the best you can do is the dialynx 50/50 haldex controller.

 

[god_thats_quick]

If the front wheels are on ice for example it will take very little torque for them to spin, so all the rest of the torque will be sent to the rear is how I think the guy from Haldex was suggesting it would happen.

 

[kazino21]

So basically car will always understeer profusely when pushed hard.

 

[god_thats_quick]

I'm not sure that's really a fair way to put it, but yes all Audis tend to be designed to understeer on the limit rather than oversteer, however if its wet I can get my car to oversteer on power very happily on roundabouts and very rarely experience understeer.

 

[madvw]

[ QUOTE ]
If the front wheels are on ice for example it will take very little torque for them to spin, so all the rest of the torque will be sent to the rear is how I think the guy from Haldex was suggesting it would happen.

[/ QUOTE ]

the torque will still be split 50/50 though, as there is no way to reduce the power delivery to the fronts. The S3 is a FWD car, with the option to deliver 50% of the torque to the rears if is see's the fronts spinning.

When they do slip, the rears are engaged, but they dont stop the fronts from spinning.

If the fronts were somehow braked, or power that was being delivered to them reduced, then it would result in the power being delivered to the input of the haldex being reduced too.

Anyone got a picture of the S3 drivetrain to explain this, as i cant find one anywhere?

 

[madvw]

this kind of explains what i'm tring to say:

The engine output is fixed to to front axles, and the haldex axle.

the only part of the drivetrain which is "optional" is the rear axle, as its being varied by the haldex clutch.

 

[god_thats_quick]

Yep the front wheels are always driven but why do they have to use 50% of the torque If they're just spinning away?

As I understand it all of the engines remaining torque is transmitted to the rear axel. I was just trying to find the article where this question was answered in more detail, there are references in WAKs link to 100% being transfered to the rear wheels but I think 100% is not technically possible. You should be able to get pretty close in the 100% slip front / 0% slip rear so ICE / Tarmac type situation though from what I've read.

I'll have another look later and see if I can find the bit I'm thinking of.

 

[The Slug]

So lets say in wet condistions on normal road surface, if the front axle is locked say, then surely blastin from a stand-still the front wheels would always spin, but this isnt the case. If you get my 'Drift' lol

The car always seems to just grip impressively..

 

[madvw]

the question still remains though:

If the mechanics that drive the front wheels also drives the input shaft to the haldex - how can reducing the torque to the front wheels not affect the torque delivered to the haldex?

 

[The Slug]

doesnt it all work thru the electronics as opposed to mechanics???

 

[madvw]

the haldex electronically engages the rears, but the haldex input shaft is surely connected straight into the gearbox?

 

[god_thats_quick]

[ QUOTE ]
So lets say in wet condistions on normal road surface, if the front axle is locked say, then surely blastin from a stand-still the front wheels would always spin, but this isnt the case. If you get my 'Drift' lol

The car always seems to just grip impressively..

[/ QUOTE ]

The answer to this is in the definition of wheel slip, this is not the same as the wheels actually spinning, so even before the front wheels have lost grip completly the power is transfered to the rear. Again this is from how I understand the system so my apologies if I'm wrong - but I don't think I am.

 

[god_thats_quick]

[ QUOTE ]
the question still remains though:

If the mechanics that drive the front wheels also drives the input shaft to the haldex - how can reducing the torque to the front wheels not affect the torque delivered to the haldex?

[/ QUOTE ]

To be honest I'm not sure how the transfer part of the gearbox works 100% so wouldn't like to comment, I'll try and find out though.

 

[madvw]

nice one dude, that would clear things up /ubbthreads/images/graemlins/smile.gif Happy to be proved wrong as always /ubbthreads/images/graemlins/beerchug.gif

 

[madvw]

anyone else able to clear this one up?

 

[Khufu]

not even having one, I always assumed on the S3 that the power always went to the front wheel and via a electronically controlled cluch (hadex) to the rear wheels if the system detected the front understeering. I believe it can, as Madvw says can never transmit more than 50/50. Also you have to take into account the ESP too. This can affect the delivery of power too by controlling the ABS depending on lateral/longitudinal forces combined with the angel of the steering wheel.

enough ranting, back to my piniot grigio /ubbthreads/images/graemlins/smile.gif

 

[Paul-RS6]

having run mine in the past very briefly in 2wd
(very easy to replicate) i have come to the conclusion that the car is far more in 4x4 than people gigve it credit for.


especially if remapped.

On a dry road, from a rolling start if i plant it, I get massive wheel spin and torque steer.

reinstate normal haldex control, and it just isnt there.

So if you are "pressing on" and like a bit of brisk acceleration, your more often than not be using 4x4


its so obvious when tested this way it almost makes me wonder the benifint of the upgrade haldex controller.

 

[ianhg]

get an uprated haldex controller and it makes the car more neutral

 

[jojo]

Hi guys, just giving my personal description of how Haldex work on our A3/S3s

Essentially, the front wheels are 100% driven directly from the transmission like any 2WD A3, but from the side of the gear box(I think?) is a prop shaft that goes to the rear of the car where the Haldex coupling is situated, which is actually a clutch that operates/controls the amount of drive the rear wheels get.
During normal driving, the Haldex is usually doing sod all, so the car behaves like a 2WD motor, with the rears disconnected from the fronts. When things start to get serious for the driver, and the car senses slip between the front and rear axles, then the Haldex is engaged to deliver power to the rears, and gives us 4WD.
Now here comes the technical bit with regards to power distribution, when the Haldex is fully engaged, the car will have 50:50 drive to the front and rear wheels, so the power distribution should only ever be 50:50 max between the front and rears. It is Impossible for any more than 50% of the drive to go to the rear axle with this setup, as the fronts are directly connected to the transmission as mentioned above! Now with regards to having the ability to transfer 100% of the power/torque to the rear wheels in extreme conditions, picture this, put the front end of your A3 Quattro on axle stands(lets say the axle stands have castors on them) and the rear wheels are on the ground. Now if you try to pull off in 1st gear, the fronts will start to rotate, then all the electrics come into play and engages the Haldex, and there is drive to the rear axles pushing your Quattro forwards. In this 'Extreme' condition, the front will be free wheeling(they are off the ground!), as they need to rotate to give drive to the rears, so the drive is still 50:50, but as only the rear wheels are pushing the car forwards, all the torque is going to the rear of the car!.
There we have it, It's been a long night, and I wanted to get this off my chest. /ubbthreads/images/graemlins/tongue.gif

Hope that has made it more clear to anyone whose read this far lol. /ubbthreads/images/graemlins/grin.gif

Any more questions on Haldex, form an orderly queue over here. ---->

 

[jojo]

Oh, forgot to add, that the standard Haldex ECU uses a combination of sensors like wheel speed, throttle position and the amount of slip between the front and rear axles to control the amount of drive required directed to the back. An uprated Haldex ECU, from what I have been reading, engages the Haldex dependant on throttle position, so when you bury the throttle, it will fully engage/lock the Haldex clutch before the power is transmitted, giving a better response and proper 4WD without any delay. Phew!

 

[ianhg]

nice one