Torsen vs Haldex

[Dave]

In truth, with a few differences in the detail, I think the latest incarnations of Torsen and the Subaru AWD systems are pretty similar. .

Agreed, I think they are practically the same. maybe slight difference in the diff?

[garcon magnifique]

I think design of the diff is probably different, but the way it makes the awd work is similar, if you get me.

The main advantage my STI has over most (all?) Torsen Audis is a switchable and lockable diff control - first time I've used the diff lock is the last couple of weeks and it certainly helps in dragging the car up snow covered inclines.

[Dave]

I have a diff lock in my Q7 (although I don't think it's an option in many other audi's). I have to turn off and hold down the ESP and then it enters locked 4 wheel drive mode! (not for use on roads apparantly)

[scooby_simon]

I've driven the Subaru AWD and Haldex in an R32 hire car and I found the R fine for motorway plodding, but as soon as I booted it on any loose surface I was never sure exactly what would happen. Dave's example of the slide and boot it; whaty would Haldex have done.

I did feel the power moving around on the R32. Nice car, but a little unsettling for me..

[Dave]

I did feel the power moving around on the R32. Nice car, but a little unsettling for me..

Exactly right.. I'm not dissing Haldex at all.. it's a good system, but once you've driven a good torsen car you can feel it's not the same.

[mb]

In my opinion, once you have lived with Torsen , haldex will always be a compromise.

That is interesting - I am certainly happy with Torsen but find Haldex a bit "easier going" - do remember I used to "load up" the Golf early as didn't like the way Haldex would cut in otherwise so look forward to getting more used to Torsen !

What is the advantage of locking the diffs apart from off-road as surely this must make it hande like a trailer on the road (I think you could change the diffs on the ur quattro) ?

[Dave]

Yes, you wouldn't want to lock the diffs unless you were off road..

basically it means that all 4 wheels turn at the same speed (normally,when you go around a corner the outside wheel travels further than the inside wheel.. the diff allows this to happen). If you lock the diff then you will scrubb your tyres on tarmac as one will not be able to go faster than the other.

[garcon magnifique]

Locking the diffs up ensures all four wheels will always be turning at exactly the same rate irrespective of grip - hence better on a loose surface and mud/snow, but not advisable on tarmac unless you want to explode your diff.

[Mook]

I think design of the diff is probably different, but the way it makes the awd work is similar, if you get me.

The main advantage my STI has over most (all?) Torsen Audis is a switchable and lockable diff control - first time I've used the diff lock is the last couple of weeks and it certainly helps in dragging the car up snow covered inclines.

The Audi diff is fixed torque distribution. Depending on which model you have depends on the distribution (Audi have started chucking more torque the rear with the RS4, S5 etc).

I think people need to get out of the whole "Torsen" thing though - that's just the name of the design of a diff, not the whole AWD system.

The difference between the Scooby (and Mitsu Evo) AWD systems and Audi etc. is that the torque split can be varied front to rear, manually with the Scooby and automatically with the Evo

[Dave]

True, but it's the diff that makes all the difference : Torsen - Wikipedia, the free encyclopedia

Basically it controls how much power goes front or rear. It's a mechanical piece of equipment.. connected to the diff is a drive shaft that powers front and rear.... whereas in a haldex it is controlled electronically.

And did you know that the 5th generation of Haldex is due next year? Haldex Traction - Wikipedia, the free encyclopedia

[garcon magnifique]

The difference between the Scooby (and Mitsu Evo) AWD systems and Audi etc. is that the torque split can be varied front to rear, manually with the Scooby and automatically with the Evo

With the latest version of the Scooby AWD, it's also automatic - with a manual override in the STI.

[Scotty]

The Audi diff is fixed torque distribution. Depending on which model you have depends on the distribution (Audi have started chucking more torque the rear with the RS4, S5 etc).

The whole A4 range (and therefore I guess A5 and others) now get 40F/60R.

It certainly makes a difference.

In my TT booting it out of a junction always meant I was risking the front's starting to spin, power going to the rear at the same time as power was cut meaning it was a mess and you're stuck in the middle of the road with a lorry coming and you're going nowhere fast.

My B6 S4 was enlightening to say the least. The predicatability and confidence it gave was an incredible change to the TT and made it very easy to drive fast.

My B8 A4 is simply better again. You get more sense of being pushed and it certainly gets you around the bends better. In the snow it was certainly more entertaining as in those conditions it (when playing about) it was certainly tail happy.

Edited January 18, 2010 by Scotty

[Milo]

Hmmm, this is not inspiring me with confidence.

I went for quattro last time as the previous A4 suffered from terrible traction and wheelspin and the understeer in corners was positively dangerous. Almost 4 years have since passed (since I got the first rejected quattro car) and I've become quite used to how it behaves i.e. I know it's never going to wheelspin and leave me stranded at wet junctions like the old one did and also I know how it behaves and feels in corners (very solid).

Now I'm sure I would learn to understand how the Haldex system on an S3 behaves but a lot of what's been written seems to undermine the very reasons I wanted quattro in the first place.

I need to get a test drive organised but it'll need to be unaccompanied I think......

[Mollox]

Say what you want about Haldex, and yes, it is a cheaper, less sophisticated alternative to Torsen - however - the earlier generation Haldex on my old S3, whilst crude, still achieved terrific drive out of wet junctions and succeeded in putting down 100% of the (remapped) power >90% of the time.

Can't say the same for the Whattro? in the RWD M3...

ETA: The S3 coped very well (traction-wise) in the snow. Certainly, I had no idea of the perils of my car park until I got the BMW. And one of my favourite memories was arriving at the car park at a rain sodden (complete mudfest) Badminton and being stopped right in the middle of a huge puddle by a marshall telling me that there was no way I'd get through. Red rag to a bull. Cue 1st and a bootfull of gas, mud flying absolutely everywhere and the trusty Haldexed S3 took off like a scalded cat

[scooby_simon]

With the latest version of the Scooby AWD, it's also automatic - with a manual override in the STI.

Manual override first came to UK spec models with the WR1, if you call the WR1 a true uk spec model.

[garcon magnifique]

It did, and yes I would.

[Chris_B]

The Audi diff is fixed torque distribution. Depending on which model you have depends on the distribution (Audi have started chucking more torque the rear with the RS4, S5 etc).

Err, no, it's just the "default" distribution that is in effect when both front and rear have equal grip. The 60/40 split can go to 85/15 rear-biased and although I can't remember the maximum front-biased transfer that's possible, it's something along the lines of 35/65 IIRC.

It's torque sensing, so it's completely automatic and has an effective response time of zero. However, the cost is twofold - you can't tow a Torsen-equipped quattro on two wheels as you knack the diff, and if you lose any grip at all on one front wheel and one rear wheel, you tend to get a bit immobile!

I've not yet driven anythign with the torque vectoring on the rear axle, but that is essentially like a haldex (as in it's a multi-plate clutchpack) to distribute torque between left and right rear wheels, with a regular Torsen to distribute between front and rear axles. That sounds like not only giving better dynamics on road, but if you have some traction on either rear wheel, you'll be able to move. I must try one some time!

[Scotty]

Err, no, it's just the "default" distribution that is in effect when both front and rear have equal grip. The 60/40 split can go to 85/15 rear-biased and although I can't remember the maximum front-biased transfer that's possible, it's something along the lines of 35/65 IIRC.

It's torque sensing, so it's completely automatic and has an effective response time of zero. However, the cost is twofold - you can't tow a Torsen-equipped quattro on two wheels as you knack the diff, and if you lose any grip at all on one front wheel and one rear wheel, you tend to get a bit immobile!

I've not yet driven anythign with the torque vectoring on the rear axle, but that is essentially like a haldex (as in it's a multi-plate clutchpack) to distribute torque between left and right rear wheels, with a regular Torsen to distribute between front and rear axles. That sounds like not only giving better dynamics on road, but if you have some traction on either rear wheel, you'll be able to move. I must try one some time!

I don't full understand how it works but whne playing in the snow the tail was definately more lively than my old B6 S4. I get that 40/60 is the default and also about the max transfers but I don't understand how it works and feels tale happy :confused:

I also tried the near side wheels on sheet ice and the offside on the road and it pulled away absolutely fine. :confused:

[Frodo]

Err, no, it's just the "default" distribution that is in effect when both front and rear have equal grip. The 60/40 split can go to 85/15 rear-biased and although I can't remember the maximum front-biased transfer that's possible, it's something along the lines of 35/65 IIRC.

It's 30/70 according to All Wheel Driven - Audi's quattro generations

It's torque sensing, so it's completely automatic and has an effective response time of zero. However, the cost is twofold - you can't tow a Torsen-equipped quattro on two wheels as you knack the diff, and if you lose any grip at all on one front wheel and one rear wheel, you tend to get a bit immobile!

Cue VT;

[AZURES3]

This site seem to give you all the answers.

All Wheel Driven - Audi's quattro generations

Torsen is now at generation 5 and is a 40:60 split from to rear. The site has some great videos to show how the generations have changed the way cars handle.

Haldex is now at generation 4 and should now be proatcive rather than reactive due to the pretensioing.

All Wheel Driven - Haldex all wheel drive system

Again from the site it would suggest Audi has only used generation 1 and 4 of the Haldex system:

All Wheel Driven - Audi all wheel drive explained

Oh and as a disclaimer and some very wise words this is an excellent summary of 4WD/AWD as a safety feature

All Wheel Driven - All wheel drive safety concerns

And just for completeness here is the Scooby stuff which from the comments looks less easy to understand as they seem to change between versions and even countries with the same model.

All Wheel Driven - Subaru all wheel drive explained

HTH

Just for clarity they have used Haldex generations 1, 2 & 4

[Chris_B]

I don't full understand how it works but whne playing in the snow the tail was definately more lively than my old B6 S4. I get that 40/60 is the default and also about the max transfers but I don't understand how it works and feels tale happy :confused:

I also tried the near side wheels on sheet ice and the offside on the road and it pulled away absolutely fine. :confused:

Yep, I noticed a massive change between the W12 and S8 - in theory the biggest dynamic change was the swap to rear-biased centre diff.

Why I think they feel tail-happy under power is the same reason RWD cars are tail-happy. The fronts can do more steering within available grip, and the rears do more pushing forwards. Exceed Kamms circle on the rears and they start to slide sideways because the centripedal force created by cornering is trying to push the whole car sideways, only the fronts are able to divert nearly all the grip to sideways grip and don't slide, unless you're really overcooking it - go into a corner fast enough in a RWD car and you'll just slide diagonally.

I suspect there's less tyre-smoking action when a rear-biased Torsen breaks the rears away compared to a RWD car because the torque gets shunted off to the front by the time you light the rears up.

I've never managed to get the rears loose for long, and I always found it easier on wet roads with ESP turned off, otherwise one rear wheel is braked, and the centre diff loads the torque forwards again.

Of course, overall vehicle dynamics depend on weight distribution, transfer (suspension and anti-roll etc) and the like. I'm quite sure the D3 S8 is mechanically a more dynamic car than the RS 6, but the RS 6 has the ability to turn ESP mostly off, unlike the S8 which only does partial off. The RS 6 still pushes the nose wider sooner though, and needs more heavy boot into corners to counteract it. I thought the S8 was quite well balanced for such a big car, actually.

[IanHo]

I don't full understand how it works but whne playing in the snow the tail was definately more lively than my old B6 S4. I get that 40/60 is the default and also about the max transfers but I don't understand how it works and feels tale happy :confused:

I concur with Scotty defiantly tail "happy" in the snow but just so controllable (I have the sports diff as well). My old B7 quattro really impressed me last year in the snow when I had to take my lad to hospital. There is a really steep hill up to this hospital no cars were going up, a gritter was coming down the hill and sliding all over the place. I had no choice but to give it a go and went up with no drama at all a bit like the A6 ski jump advert but with no safety rope! The B8 is better again I've had a few "moments" in the snow but you never think you are out of control I'm sure the sports diff is playing it's part here as well.

Just coming up to 6 months with the S4 will be posting a detailed review soon.

Edited January 19, 2010 by IanHo

[Mr Man]

Hmmm, this is not inspiring me with confidence.

I went for quattro last time as the previous A4 suffered from terrible traction and wheelspin and the understeer in corners was positively dangerous. Almost 4 years have since passed (since I got the first rejected quattro car) and I've become quite used to how it behaves i.e. I know it's never going to wheelspin and leave me stranded at wet junctions like the old one did and also I know how it behaves and feels in corners (very solid).

Now I'm sure I would learn to understand how the Haldex system on an S3 behaves but a lot of what's been written seems to undermine the very reasons I wanted quattro in the first place.

I need to get a test drive organised but it'll need to be unaccompanied I think......

What were those reasons?....having read this thread and the associated links it appears the latest pro-active Haldex IV system switches to 4wd only when you need it.....No delay in engaging the rear axle as per generation I+II....I suppose the advantage of Haldex is better fuel consumption and no drive chain power loss when driving normally....ie 99% of the time....and when you need it; drive is transferred to all 4 wheels in an instant, thanks to the magic of electronic wizardry

As you say a test drive is the only way to determine whether this system delivers what you want....but I suppose the only way to really assess the pro/cons of the Haldex set up would be to test it on a track when you can push it to the limits legally.

"I need to get a test drive organised but it'll need to be unaccompanied I think"......Deffo:grin:.

Edited January 19, 2010 by Mr Man

[Milo]

When people start talking about it being twitchy or feeling a surge as the rears kick in mid corner it puts me off. I never seem to get above 30mph these days but on those occasions when I want to, I don't much like the idea of surges or twitches

I could be being over cautious but I'm sure a test drive would answer it either way.

As it is, I had a good pour over a Sportback yesterday and I'm not sure it ticks all the boxes for what I need.

If I'm buying a quattro car I want to know it's going to be nothing other than solid in how the system behaves when driving, errrr, enthusiastically

Edited January 19, 2010 by Milo

[Mr Man]

I see what you mean.....for some reason I can`t recall ever reading an independent;back to back,road test comparing the Torsen and Haldex systems....It`s the sort of test/comparison you`d expect the likes of Evo magazine to have done at some point.....as the Haldex vTorsen argument has been raging for years.....Basically is a Haldex equipped car really 4wd?...some would say NO....others would say yes...but only when needed.....and can Audi justifiably put the Quattro badge on a car fitted with the Haldex system?

Personally....if I wanted an S3....which I do.....The fact that the car is not permanently 4wd would`t bother me.....I tested an A3 2.0tfsi (200bhp)quattro 4 1/2yrs ago and I thought it was fine......but I did`t exactly push it....It was a baking hot summers day, so I would have been seriously chancing my luck if I`d tried to take it to the limit....even on the deserted back roads of Anglesey.....but I could`t get the front wheels to spin up....something that is`t too difficult to achieve on the fwd car I have. I was going to buy one until I tested a DSG equipped car and then I decided I wanted that gearbox.At the time it was Quattro or DSG....sadly you could`t have both.

Edited January 20, 2010 by Mr Man