daniel mason
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| posted on 21/7/10 at 06:04 PM |
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torsen diffs? vs lsd
can someone please explain the term 'torsen' diff (sorry if i spelt it wrong) and explain how it differs from an lsd? cheers
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hobbsy
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| posted on 21/7/10 at 06:16 PM |
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Torsen = TORque SENsing and is a type of LSD.
Other types of LSD's (like what you're probably referring to) are:
Viscous (like a Sierra 4x4 rear)
Plate / Clutch type
Torsen diffs use gears.
Check the quaife site for a better explanation than I can give.
Or just read:
http://en.wikipedia.org/wiki/Limited_slip_differential
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SeaBass
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| posted on 21/7/10 at 06:17 PM |
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All about Torsen / Torque Sensing
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hobbsy
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| posted on 21/7/10 at 06:23 PM |
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Heheh I always forget about LMGTFY! 
Maybe I should send myself a link:
http://www.lmgtfy.com/?q=let+me+google+that+for+you
But I need to be careful I could end up in an infinite loop!  heheh
[Edited on 21/7/10 by hobbsy]
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Litemoth
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| posted on 21/7/10 at 06:29 PM |
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My understanding is that an LSD allows a certain amount of slip (difference in rotational speed beween the two wheels across an axle) whereas
the Torque Sensing option does it by sensing the resistance to movement and sending the power to the wheels in proportion to the resistance to
turning 'felt' on that wheen (i.e. most grip)
It seems that they have a different handling & grip characteristic for the driver. The torsen is permanently engaged is smooth and gradual whereas
the LSD 'switches' in when you have reached the 'limit' of the slip.
Wish I still had my Hillier and Pittuck book - those chaps explain it so much betterer
[Edited on 21/7/10 by Litemoth]
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turbodisplay
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| posted on 21/7/10 at 07:13 PM |
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The only dowside to torsen is that if there is no torque one one wheel (ice patch) the other wheel will have no torque.
Torsen requires some torque in the lower grip, and sends a multiple (about 5x) to the other wheel.
If there is no torque on one wheel the other gets 5 x 0 = 0.
Darren
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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v8kid
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| posted on 21/7/10 at 07:22 PM |
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Hey Darren thats the best description of a Torsen diff I have heard - got it in a nutshell and thats just the way it works in practice 5*0=0 but 5* a
bit is a lot more!
You'd be surprised how quickly the sales people at B&Q try and assist you after ignoring you for the past 15 minutes when you try and start a
chainsaw
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snapper
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| posted on 21/7/10 at 08:46 PM |
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Reading the Wiki gave a trick you can use which is to apply the handbrake which will cause drag to the free spinning wheel therefor allowing the
TorSen to load torque to the wheels
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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hobbsy
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| posted on 21/7/10 at 08:55 PM |
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Snapper - good tip if you're on ice but no so good if you're riding kerbs on a trackday and the wheel is leaving the ground.
Generally I'd say the Quaife ATB (torsen) is the best but then I'm biased as I have one in my car
Its also a lot more money than fitting a vLSD from a 4x4 Sierra.
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Neville Jones
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| posted on 21/7/10 at 09:12 PM |
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quote:
Originally posted by turbodisplay
The only dowside to torsen is that if there is no torque one one wheel (ice patch) the other wheel will have no torque.
Torsen requires some torque in the lower grip, and sends a multiple (about 5x) to the other wheel.
If there is no torque on one wheel the other gets 5 x 0 = 0.
Darren
Absolutely untrue!! And back to front in thinking. The torque split is the the input torque being split, NOT the road grip. On ice, both wheels would
get similar torque. Your thinking would have the diff not driving the axles at all, and the pinion spinning out of control. Think about it.
When both wheels have similar grip, they get similar torque. When one loses grip, the torque is split between BOTH wheels in the inbuilt ratio.
The torque split helps turn the car in corners. If you are doing a lot of tight cornering, you need a high torque split ratio. Big ovals, you need a
more even torque split ratio.
The torque split ratio is dictated by the inbuilt gearing ratio, and can be altered in genuine Torsen diffs by Gleeson.
I've worked with these things for far too long.
And a Quaiffe diff is not a Torsen, but looks similar internally, and is a rudimentary attempt to circumvent a very robust patent.
Cheers,
Nev.
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Liam
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| posted on 21/7/10 at 10:59 PM |
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quote:
Absolutely untrue!! And back to front in thinking. The torque split is the the input torque being split, NOT the road grip. On ice, both wheels would
get similar torque.
He said one wheel on ice, i.e one wheel with no grip, essentially the same situation as one wheel in the air. In which case a Torsen diff
behaves ilke an open dif and spins the wheel with no grip away.
quote:
Your thinking would have the diff not driving the axles at all, and the pinion spinning out of control. Think about it.
As above - it is behaving like an open diff spinning the wheel with no grip and putting 0 torque to the ground through the wheel with grip.
I ought to say I've never used one, but everything I've ever read or heard about Torsens reports that limitation. That and the fact there
are techiques developed to escape from that very situation by applying some drag to the wheel with no grip/in the air with the brakes/handbrake so
that the diff can apply that drag x the bias ratio to the good wheel, gives me little doubt the situation is real.
But maybe you're right and everyone else is wrong?
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jeffw
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| posted on 22/7/10 at 05:50 AM |
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The Audi Quattro system uses Torsen diffs in the centre and, on some cars, the rear diff (note the A3 platform uses the Haldex system and is quattro
not Quattro in Audi speak). I've had, the past 7 years, a 440BHP Audi B5 S4, 550BHP B5 RS4 and currently a 300BHP A6 3.0TDi and I can safely
say I have never had the situation described above. I've used the cars on snow & ice and trackdays.
[Edited on 22/7/10 by jeffw]
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v8kid
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| posted on 22/7/10 at 06:05 AM |
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Nev my MX5 and TR8 both have quaiffe diffs and are 5ite in snow with one wheel spinning at the slightest provocation. Aided and abetted no doubt by
the weight distribution nonetheless in practice it mirrors the description given by Darren where there is a point where the diff fails to allocate the
drive between both wheels resulting in the pinions and one drive shaft spinning out of control.
Not sure how this is back to front thinking?
You'd be surprised how quickly the sales people at B&Q try and assist you after ignoring you for the past 15 minutes when you try and start a
chainsaw
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Neville Jones
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| posted on 22/7/10 at 09:09 AM |
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A Quaiffe is NOT a Torsen, as I pointed out. A proper Torsen will ALWAYS give drive to the wheel with most grip. Mechanically impossible to do
otherwise.
The Audi has proper genuine Torsen diffs, so no probs.
Don't ever try jacking up one corner of a car with a proper Torsen diff to check if it works, by applying power with one wheel in the air. The
car WILL jump off the jack. A Quaiffe will spin up the free wheel, more often than not, as it relies on the lower grip wheel to apply some resistance
so that the internal gears can grab on the housing. A Torsen operates very differently to a Quaiffe.
Cheers,
Nev.
[Edited on 22/7/10 by Neville Jones]
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Liam
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| posted on 5/8/10 at 08:46 PM |
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Stumbled on this video and thought of this thead .
Torsen diff (centre in this case) behaving as an open when one output can support no torque...
http://www.youtube.com/watch?v=Oo9GV4mSnRQ
Apparently that's 'mechanically impossible'. Fake vid i guess, then
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