The Cal-look Lounge

What would be more benificial for dragracing and why?: a Limited Slip diff like a ZF unit or a Torque biassing diff like Quaiffe makes?

Tnx,
Walter

Quaife.
You break it, they'll replace it.

So does Paul Guard from GT diffs who provides more than excellent LSD diffs.
Question however is not which brand is the best quality, but why would you choose a torque biassing diff and not a Limited Slip diff? They work quite differently in operation as I understood, but what is the best type for dragracing and why?

Well, if it's strictly a drag racer, get a spool ;)

Nah, I want to drive to a drag race, not trailer queen her... :D
And I consider a spool dangerous: when it breaks, you drive straight into the wall, hard.

But nobody know the difference between LSD and a TB diff and what would be better suited for what application? Hmmm...

A clutch type LSD like a ZF provides limited slip action on both acceleration, and deceleration.  If you want to get fancy, you can alter the accel lockup % to be different from the decel lockup %.

A TBD like the Q provides biasing on acceleration only.  On decel, it is an open diff.

With the ZF, if you break an axle, you have a gearbox full of neutrals.  No ass-puckering turns.  I don't know what happens with a Q when you bust an axle.

Adding to what Bruce said because an LSD works on deceleration they cause understeer on cornering when off the power.

Ok, yes, that is what I read after some googling as well. However, ALL the track going porsches use a LSD, so there must be s/th more about it you'd think.
I am also curieus what the difference in 'lock-up' is between a LSD and a torque biassing diff on acceleration during say, a drag race start. Also curieus what would help more for straigh line stability, a LSD or a TBD or maybe it doesn't make a difference.
Good q. Bruce on what would happen if an axle broke on a TBD! I dunno either. Maybe someone 'in the know' could chime in  ::)

What kind of diff would Russ Fellows and/or the 850 hp Skinne beetle have in there...?

Russ is running a Quaiffe, has done for years.

As for an axle breakage then the 'free' side of the diff will start to wind up as the diff tries to put the power to the wheel with grip. so this can have the same effect as breaking a axle on a spool, but its not as fearce as the spool. you'll have time to get your foot off the throttle.


I run a Spool and find it fine on the street. Even with my tires

Martin

Taken from the Guard website:
Limited-slip differentials provide lock-up on both acceleration and deceleration.  The amount of lock-up on accel and decel can be adjusted by selection of the internal plate sequence.  Lock-up on deceleration allows aggressive entry into a turn and late braking, reasons why all Pro race teams (that we are aware of) utilize LSDs, rather than TBDs.

Torque-biasing differentials provide lock-up on acceleration only.  The amount of lock-up (5-80%) increases as the amount of torque increases.  On deceleration, lock-up is negligible, making the TBD the ideal diff for the slower speed turns of autocross.  (In the same slower-speed turns, an 80% LSD would most certainly cause understeer.)

A torque-biasing differential performs like an open diff whenever one of the two drive wheels lifts off the ground.  Lock-up and traction are lost until both drive wheels are again planted firmly on the ground.

So from that if you broke an axle with a TBD, because there will be little or no resistance and torque the diff goes back to being like a stock open diff and should not cause a hard turn into the guard rails!

An LSD is better for circuit racing, so as the Quaife is actually a TBD does anyone make a LSD for VW transmissions? Just ZF?

Rob.

Judging by that report, I'd rather have a LSD in an all purpose street car.

The one I saw with a Quaife that broke off the type 1 splines stayed at the start line and did no move.

You also have to factor in a couple other things when you make your decision.

-Can you actually get either (torque biasing or limited slip) so there is a decision to be made?

-If it does blow up, can you get parts, or another diff?  VW swing ZF's are getting more and more scarce, while the Quaife has a warranty.

-With the supply of limited slip diffs being, well, limited- what shape is it going to be in if you get one?

On paper, the limited slip sounds like a slightly better option for drag racing or street/strip.  In the real world, it hardly makes a difference.  I've driven and raced both with decent power 180+hp and they both work just fine.  My type 1 box has had a ZF in it since the day it was built and I love it, my new box has a peloquin torque biasing diff in it because it was a more realistic option of actually being able to find in the first place.  As long as you are able to run something other than the cast super diff you are in good shape.






...plus, donuts are fuuuuuuuuuunnnnn.   ;D

After breaking 2 super diffs the last 12 months (broken spyder gears) I was lucky to get a ZF LSD in good condition and raced it for 8 runs on the quartermile...until....the spyder gears broke once again. :-\
Until the LSD broke it was fantastic. No more one-wheel burnouts and really good traction. I didn´t even realize that it was broken until I came back to the pits where I had to do a 180° turn...it sounded very familiar to my formerly broken super diffs so racing was over for that weekend.
My plan was to weld one of the formerly broken super diffs (low-budget spool) but luckily a friend of mine ordered some Quaife TBDs some months ago which arrived in germany 3 days ago so I will be able to try that at first... ;)

Tobi

This is a valid point as I said before apart from an second hand ZF can  you get an LSD for the type 1 or 2 transmission? Both the Quaife and Peloquin are torque biasing. And Guard is Porshe.

Rob.

Yes, its a valid point indeed, but I was firstly curieus about the best solution without cost or parts availability being a concern  ;)

I ran a 915 and will probably step up to a G50, both of porsche-make and as you pointed out very accurately, Paul Guard sells both types for these trannies  ;D

The fact that Russ chose a TBD does mean something to me in this respect. I hope he made a deliberate descision to buy a TBD and not because a friend had one lying around...
I like the LSD better from a mechanical point of view and its dual purpose caracter, but the fact that it does give some understeer on the track/street makes me a bit more biassed towards TBD at this moment... Understeer is something I have already enough, specially at slower slaloms/autocross-like events..

Hi Walter
One of my friends have been into cucuit racing with Porsches 911's and 914's and he says that aTBD if the fastest way to loose a race. When cornering the inner rear wheel can loose contact with the pavement and this wheel will spin like  cracy and no power is transfere to the outer wheel, As long as both rear wheels have contack the TBD is ok.  With a LSD some power(dependig on the diff proncentage) will allwas be tranfered to the outer wheel even if the inner wheel is in the air.  Porsche uesed a spool in their LeMans 935 racecars because they needed all the tracktion they could get and because the 935 engines broke all kind of diffs. Porsche did'nt want to quit the race because of a broken diff.  The LSD will wear out in some time and will need some attention/rebuild. THe TBD is maintaince free.

/Rolf

Thanks for sharing the experience Rolf!  ;)