# TTS - gen 2 Haldex change



## kmpowell (May 6, 2002)

I recall reading that early TTS' have an older version of Haldex?

If I am right (and I'm not dreaming that I read it!) does anybody know off hand what the cut-off date was last year when Audi changed the Haldex in the TTS to Gen 2?

TA


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## Toshiba (Jul 8, 2004)

kmpowell said:


> I recall reading that early TTS' have an older version of Haldex?
> 
> If I am right (and I'm not dreaming that I read it!) does anybody know off hand what the cut-off date was last year when Audi changed the Haldex in the TTS to Gen 2?
> 
> TA


That's correctish, the 'TTS' has always had the same controller, but its an updated one when compared to the 'other' models.
Its able to react faster.

I'll post the stuff up again later on.


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## kmpowell (May 6, 2002)

Thanks Tosh - so all TTS' have the same controller, there have been no upgrades?


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## ross2280 (May 11, 2005)

kmpowell said:


> Thanks Tosh - so all TTS' have the same controller, there have been no upgrades?


If i recall the haldex thread, there has been no change within the TTS production dates to the haldex itself. It was different to begin with, i.e. more recent than other audi models.


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## kmpowell (May 6, 2002)

ross2280 said:


> kmpowell said:
> 
> 
> > Thanks Tosh - so all TTS' have the same controller, there have been no upgrades?
> ...


Ta


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## Black Knight (Jan 16, 2007)

would it work if installed on a 3.2?


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## Arne (Dec 13, 2006)

I sendt this question to Haldex Traction System Divisjon 10.july 2008:



> Hi,
> 
> I was wondering what kind of Haldex system (which generation) is used in the new Audi TTS (272 hp, 2009 mod)? And what is the\"normal" power distribution (front/rear) under dry conditions (steady power)?
> 
> ...


The answere I got was this (and it will answere your question as well):



> Hello Mr xxxx!
> 
> In the new Audi TTS, 2009 model is Haldex Generation IV. Regarding your second questions we can say that since the coupling continuously reacts on the driving conditions it is hard to determine a "normal" power distribution. Therefore it´s hard to provide you with a statement in percent or a figure.
> 
> ...


The big differense between gen 2 and gen 4 Haldex is that gen 2 is "reactive" (it reacts when one or more of the wheels loose traction), while gen 4 is "proactive" (it reacts on throttle and steering input, so the power distribution will change before traction is lost - and it also reacts on loss of traction way faster than 2 gen).


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## Black Knight (Jan 16, 2007)

yes yes, that's all software practicaly... performance haldex controllers have been available for even the mk1 TT that do exactly that - work proactively using throttle and steering.

but the real question is, does the TTS have a different haldex coupling - hardware.... what i summed up from the marketing mumbo jumbo is that gen IV haldex installation also includes an updated haldex coupling that features an extra electrical pump and pressure accumulator. it is there so the "proactive" controller always has some pressure to work with.

old haldex coupling are supposed to create pressure solely from the difference in shaft rotation. when one shaft rotates relatively to the other(front to back) pressure is created which allows for the clutch to bite. it is controlled electrically by the controller but the controller can only choose not to use the pressure generated and if there is not pressure generated it can do diddly squat. whereas the new haldex coupling has the extra pump and doesnt rely or need the shaft speed difference to pump up the pressure - it can pump it up without slip ever occuring.

obviously, using the electric pump the gen IV haldex should be able to keep the rear wheels powered even when there is no slip - but i doubt it actually does that unless you mash the throttle or steering. it would wear out too soon, cause the car to skip(like having the differential blocked on SUVs) increase drivetrain drag by A LOT and consequentially fuel consumption. so i'm 99% gen IV has the same "torque split" as any haldex - almost no torque is sent to the rears during steady driving.

now, i want to know if i got all this right? and if i did, this should be the end of all haldex talk.

and no, no generation of haldex is able to send more than 50% of torque to the back if all wheels have the same grip. front wheels cant be disconnected by any means - there's no front haldex clutch - so the haldex can at best rob them of half the torque.


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## Arne (Dec 13, 2006)

The question here was if all the TTS has the 2. or 4. gen Haldex - and the answere is 4. gen.

For anyone who needs more info about the Haldex 4. gen, you can read your eyes sour here:

http://www.haldex.com/en-gb/Europe/Appl ... ories/AWD/


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## der_horst (Apr 29, 2006)

the haldex-update was a silent update done at first for the tts. so all tts have the latest version. within a couple of weeks audi upgraded it's production completely though, so that all awd tt have the same haldex hardware as the tts has.

i don't recall the build weeks when which engine variant was updated, but i'm sure it's somewhere in this forum. if you can't find it but it's somehow important i can search for the corresponding thread in the german forum where i know it was listed


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## kmpowell (May 6, 2002)

der_horst said:


> if you can't find it but it's somehow important i can search for the corresponding thread in the german forum where i know it was listed


It's ok thanks der_horst. I was only checking in regards to the TTS, which the first part of your answer confirmed for me.

Many thanks


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## Singletrack (Aug 1, 2007)

der_horst said:


> the haldex-update was a silent update done at first for the tts. so all tts have the latest version. within a couple of weeks audi upgraded it's production completely though, so that all awd tt have the same haldex hardware as the tts has.
> 
> i don't recall the build weeks when which engine variant was updated, but i'm sure it's somewhere in this forum. if you can't find it but it's somehow important i can search for the corresponding thread in the german forum where i know it was listed


This begs the question asked already then....can it be retrofitted to a car fitted with Gen 2?


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## Toshiba (Jul 8, 2004)

Had a good look at this, this afternoon and it doesnt look like you can.
The new controller only appears to be used on engine code CDL (TTS and S3) from 01/07/08. The V6 is showing a totally different one. It was updated/changed on the 01/06/07 - but nothing since. Meant to check the D thing too, but i forgot. I think the engine code for that is CBB, but could be wrong.

The difference seems to be around a primer pump and the controller that drives it

I also noticed that the S3 engine BZA was changed from 07/08 to CDL variant, the same as used by the TTS.
Guess they were not the same despite many claims they were. Audi Kept that stum. Still runs at 265bhp. Does have a 256 version too


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## mikef4uk (Jan 15, 2006)

Black Knight said:


> .
> 
> old haldex coupling are supposed to create pressure solely from the difference in shaft rotation. when one shaft rotates relatively to the other(front to back) pressure is created which allows for the clutch to bite. it is controlled electrically by the controller but the controller can only choose not to use the pressure generated and if there is not pressure generated it can do diddly squat. whereas the new haldex coupling has the extra pump and doesnt rely or need the shaft speed difference to pump up the pressure - it can pump it up without slip ever occuring.
> 
> ...


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## Black Knight (Jan 16, 2007)

so, what is actually better on the gen 4 haldex unit? nothing? only the "preX" software on the controller?

selecting 50/50 on such a controller would mean a locked diff - this would eat up your rubber very fast, cause skipping in tight turns and stress the drivetrain enourmously.

select anything else than 50/50 is practicaly impossible. it's a clutch, it's not a differential, it doesnt distribute torque it only locks up.
if it locks up 50% that means it is able to maintain identical propshaft rotations speeds until the torque difference becomes greater than 50% of what haldex can take(haldex can transfer up to 2000Nm IIRC). so at 50% it can keep the propshafts running at the same speed if the torque produced by the engine and multiplied by the gearbox doesnt exceed 1000Nm... essentially - you are getting 50/50 until you exceed the limit at which point the rear bias starts falling off as the clutch starts to slip - haldex reacts by locking up more.

it is not a differential nor can it provide any other constant bias ratio. it can either allow slip or lock up. to actually be able to send a constant torque ratio to the back it would have to able to allow constant slippage and also to be able to precisely control how much slippage happens and also know exactly how much incoming torque it is getting from the gearbox.

i doubt the haldex would actually last that long while allowing constant slipping, it would wear out its clutch and contaminate the oil rapidly. 
DSG gearbox for example has a similar set of clutches and while it does allow slip and can pretty much precisely control it, i doubt it would actually last long if it was programmed for example to mimic a real slush-box - constantly allowing up to 1000 rpms difference between engine and gearbox - and that at full throttle - i doubt it would last long if it worked like that


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## der_horst (Apr 29, 2006)

Black Knight said:


> so, what is actually better on the gen 4 haldex unit? nothing? only the "preX" software on the controller?


it's a real change, not just a new firmware flashed on. there's a pressure reservoir installed at the rear that will be used to create the required pressure for the desired power distribution. in the old haldex system you needed some time of wheel spin on the front before the power distribution on the back was completely enabled as you had to build up the required pressure for the rear coupling. with the pressure reservoir you can now enable it much earlier.

the other haldex-specific limitations like maximum of 50/50 power distribution are not affected by this change, it's still just a haldex


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## mikef4uk (Jan 15, 2006)

Black Knight said:


> so, what is actually better on the gen 4 haldex unit? nothing? only the "preX" software on the controller?
> 
> selecting 50/50 on such a controller would mean a locked diff - this would eat up your rubber very fast, cause skipping in tight turns and stress the drivetrain enourmously.
> 
> ...


Yeah, it's only worked now for 2 years, eats Subaru's/Evo's off the lights and at Santa Pod, but you probably know better than the designers, I give up...................................


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## Arne (Dec 13, 2006)

Black Knight said:


> so, what is actually better on the gen 4 haldex unit? nothing? only the "preX" software on the controller?
> 
> selecting 50/50 on such a controller would mean a locked diff - this would eat up your rubber very fast, cause skipping in tight turns and stress the drivetrain enourmously.
> 
> ...


You got the link to the official Haldex site - but have you read it?

And this is all theoretical. What is most important is how it performes in real life - and have you ever tried it under different conditions?

I have, and it works way better then what I had expected - both for everyday use in dry, wet, ice and snow, and on the track.

You doubt a lot, and thinks a lot. I would reccomend that you really try it out... :wink:


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## Black Knight (Jan 16, 2007)

im not dissing the system, just trying to explain how it works and what are the most common misconceptions about the system caused by overhyped marketing taking actual facts out of context and confusing people, etc.

what am i supposed to try out? i owned a 3.2 TT mk1 and now a 3.2 mk2...

haldex is a clutch, it's not a differential. it can not offer a constant torque split. it doesnt even "split" torque. it just locks up.
a torsen differential for example on an audi A6 has an input shaft from the gearbox and two output shafts and it distributes torque to two output shafts without locking them up. watch the audi drift movie on you tube and notice how the wheels keep spinning at different rates.. haldex will never be able to do this. haldex can only allow fronts to spin up or lock all 4 to spin at the SAME speed.

however that doesnt mean driving a car with haldex is necessarily noticebaly worse(for mere humans) than other 4x4 systems... a lot of 4x4 systems use only a central viscous coupling which essentially produces similar results to a haldex coupling.

haldex can "transfer" a huge amount of torque to the rears, 10x more than a calibra turbo 4x4 with its viscous coupling for example. still, i've owned 3 calibra turbos and all of them too had loads of grip - just the same, so obviously, any 4x4 system has "loads" of grip.

any kind of 4x4 system is almost twice as better(grippier) as 2wd... proper full 4x4 systems like Evos or subarus can get extra 5-10% grip performance under certain conditions which are rarely experienced under normal driving. what also makes a difference is how it provides the grip... a constant nice torque split allows for a more predictable behavior which haldex will never be able to match, also 4 wheel engine braking etc. however i am not schumacher and neither are most of you so we hardly notice this stuff. i dont expect the car to be schumacher material either. it's a fwd laid out car with an extra clutch that lock up the rears with the fronts for extra grip.

im happy with my haldex obviously, it's twice as better than 2wd, and im not beleiving myself into silly marketing overhyped bull about haldex being the next best thing after sliced bread. haldex is a stupid clutch and the car does inherit FWD characteristics because the way haldex works and the way the car is laid out. i dont mind it and dont expect it to drive like a Evo X and i dont tell my friends stories about my haldex is rear biased or whatever. it is not and never will be rear biased nor will it ever provide a constant torque split ratio of any percentage except the maximum 50/50 which can not be held constantly for already explained reasons.

please watch best motoring comparison of audi TTS and Evo X (and some other cars, m3 etc). watch the takeoff/launch. Evo X annihilates the TTS first few yards. the TTS does actually win in the end, but the amount of grip Evo X has at the starting line obviously demonstrates that under certain conditions haldex can be spanked by proper 4x4 systems just like that, while most of the time you wouldn't notice much differences between them.


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