Hi Guys
Limited slip diffs for H165's are becoming a bit of an obsession for me.
I have one of Topgears centres and thought it wasn't working because it was spinning the inside left wheel on hard left corners. Turns out from my research that if inside wheel has no load the diff works as a single spinner until some load is on that wheel and then that will help transfer power to external wheel.(Am I right so far ?).This may confirm one of my earlier posts about dramas with the lifting of the inside rear wheel.
How do you test what preload is in a torsen type centre ?
I do not know if I am really asking a question but I would like this thread to encourage discussion on what you know about torsen lsd's so we all can learn (especially me)
Cheers
Bob

I Thought there was like a clutch pack in the gut's? that limited the diffrance through friction. and therefor were out and the diffrence can become greator? hope that makes some sort of sence?

no clutch packs involved. ther is supposed to be worm gears involved and they ar not supposed to need maintenance like clutch packs
Cheers
bob

The lubricant used in Torsens has an effect on the performance of the LSD, Also the ramp angles of the worm gears determines the lock and dis-engage of the LSD.
Give Errol from Datrats a call. He is very wised up on this type of LSD as well as others. He also has one of topgears units.

hope this helps
cheers
benny

With one wheel off the ground they will just spin the raised wheel, you _will_ lose drive.

There's no preload/adjustment on a torsen, they work on a different principle than friction type lsds do - namely that a worm gear can turn a normal gear, but a normal one can't turn a worm gear - which is about as simple as it gets in 'theory' but actually visualising the power flow through the various gears.

In 4wd applications, if one wheel comes off the ground (some sort of rocky terrain, maybe also sand dunes) then they lose drive at that entire axle. The 'trick' in those situations is simply to apply the brakes just a touch, presto some resistance to the lifted wheel spinning, and they instantly get drive on both wheels.

Of course that isn't really possible or even remotely practical in a circuit racer.

you might have to investigate altering the suspension, possibly softening rear shocker rebound in particular (so it's easier to keep the inside wheel on the road), and perhaps stiffer front bar (to keep it more level, but doing so via the front wheels, so there's less the rears have to do, they'll stay planted a little better) - but it'd probably end up sacrificing optimum corner speed. Tough call to make.


An option of sorts comes to mind. There are still side gears (so to speak) inside the torsen centres. You _might_ be able to get them coated with kevlar like material, (I'm thinking specifically here of the stuff that is used sometimes to re-line the bands of automatic transmissions for heavier duty use) - and that might provide just enough friction between sidegear (and therefore the axle) and the inside wall of the torsen itself (unfortunately, unlike a normal diff, there won't be the loading of the spider gears pushing the side gears outward under load, like there is on normal style diffs).

You'd also risk some damage to the inside of the centre (and the torsen centres discussed here of course are custom made centre assemblies, so you can't just fleece them from a std diff!

going mad (replying to myself!) - but not long after I posted that, I had another thought - but haven't had a chance to log on before now.

That thought was that - even 'if' you were to do some form of friction lining addition, the problem there would be that it'd totally compromise the main advantage of a torsen - that being that it would no longer automatically bias the torque to the wheel with the most grip (or at least it wouldn't do it anywhere near as well).

The way they bias the torque is simple enough - basically it's 'impossible' for an axle to turn slower than the tailshaft input/pinion rpm should equate to, but if a tyre loses grip, it is allowed (via a gear train) to turn _faster- - and due to the specific angles/tooth counts of the gears involved, this is possible to a maximum of anywhere up to 3-5 times the speed (depending on the specific diff and above variables). Since it's turning it (or attempting to) spin it 5 times as fast, obviously that means it'll have 1/5th as much torque by the time it gets to the wheel. So therefore by default, the other 4/5ths will go to the slower tyre. Obviously it's next to impossible to have it actually at that 5:1 ratio under most conditions, for more than an instant, (or 3:1, or whatever the diff happens to be) so it always varies from even stevens to this maximum ratio, based on how fast that less grippy tyre ends up going vs the grippy one.

On top of that, of course there are mechanical losses through the gear/drivetrain of a torsen, so you don't end up with the perfect theoretical optimal ratios/output. But it's still a sensational diff/design.

About the only other thing i could suggest, if softening the rear costs too much is to look at (legality notwithstanding) aero downforce. If that's a no no, redistribution of weight of some description might help.

Other than that, perhaps experiment with a spare centre that's welded up - and see how it goes. It does tend to promote corner entry understeer, but in a ute it probably won't be an issue, and corner exit oversteer may be a drama, but if it's moderated with the acc pedal, it still might mean better corner exit than a torsen with the inside wheel lifting off.

Hi John
Thanks for that .You have to get a life rather than trying to help out us ignoramuses all the time.
We actually have a CIG diff we are going to try and have been thinking of moving batteries and fuel tanks in an attempt to balance the vehicle if this doesn't work.
By the way did you get any joy from those scratchies
Cheers
bob