confused about diffs!

[DamoM]

So I was at the Audi Driver International day at Castle Combe and my 01E in my UR smashed a CV joint after a session.

I lost all drive and pushed it back to the pits.

What confuses me is that if you engaged gear the (broken) driveshaft would just spin and no drive would go to any other wheel. Isn't that like being on ice?

I thought that the torsen diff is supposed to automatically direct drive to the wheels with grip in that situation?

Please excuse my obvious ignorance but it really has had me baffled!

[jade]

So I was at the Audi Driver International day at Castle Combe and my 01E in my UR smashed a CV joint after a session.

I lost all drive and pushed it back to the pits.

What confuses me is that if you engaged gear the (broken) driveshaft would just spin and no drive would go to any other wheel. Isn't that like being on ice?

I thought that the torsen diff is supposed to automatically direct drive to the wheels with grip in that situation?

Please excuse my obvious ignorance but it really has had me baffled!

On The UR you have a open Diff not torsen unless fitted after-market

[DamoM]

On The UR you have a open Diff not torsen unless fitted after-market

Sorry, perhaps should have explained more clearly. The UR comes as standard with a 5 speed 016 box. I have retro-fitted a 6 speed 01E which should have a torsen?

[jade]

Sorry, perhaps should have explained more clearly. The UR comes as standard with a 5 speed 016 box. I have retro-fitted a 6 speed 01E which should have a torsen?

But that is only controlling the drive between the front and back wheels not side to side

[DamoM]

ok so if I my car has one front wheel on ice it will just spin the power away?

[Skull]

the torsen drives all the power to the wheel that hass less grip, that is the torsen downside.

if you would block that driveshaft, you would drive away.

[Skull]

ok so if I my car has one front wheel on ice it will just spin the power away?

yes this is in theory, but also on ice you have "some" grip, almost always enoug to drive the other wheels.

in real life, you are only standing still if one of your front wheels is in the air (no diff lock whatosever).

if it is one of the rear wheels you can just pull the handbrake a little just to block it from spinning, or engage the diff lock.

[Zoig]

http://auto.howstuffworks.com/differential6.htm

The Torsen (from Torque Sensing) works as an open differential when the amount of torque going to each wheel is equal. As soon as one wheel starts to lose traction, the difference in torque causes the gears in the Torsen differential to bind together. The design of the gears in the differential determines the torque bias ratio. For instance, if a particular Torsen differential is designed with a 5:1 bias ratio, it is capable of applying up to five times more torque to the wheel that has good traction.

However, if one set of wheels loses traction completely, the Torsen differential will be unable to supply any torque to the other set of wheels. The bias ratio determines how much torque can be transferred, and five times zero is zero.

This pretty much sums it up why the broken CV left the car stranded, if the Torsen could sense some torque on the front diff it would sent most of the power to the rear, but since you have open diff in the front it wont happen.

[DamoM]

Thank you guys! It all makes sense now!

[quattrostyle]

Since we are talking about diffs now I take this opportunity to discuss the V8 diff option. I'm pretty sure it has been done before but I am a tad lazy.

I got a S2 5-speed gearbox and diff, what is the real advantage/ reason I would want a V8 rear diff?

[DamoM]

Since we are talking about diffs now I take this opportunity to discuss the V8 diff option. I'm pretty sure it has been done before but I am a tad lazy.

I got a S2 5-speed gearbox and diff, what is the real advantage/ reason I would want a V8 rear diff?

I actually have one fitted in the s2 rear diff. The traction as castle Combe was incredible.

[pasbogdan]

On The UR you have a open Diff not torsen unless fitted after-market

What diff is open?

[Skull]

all 3 in the early urquattros, pre 1988...

[UrS4boy]

What diff is open?

All of the front diffs are open. Otherwise going around corners would be a bit tough.

[pasbogdan]

I was 100% that b2 q's have a torsen with locking rings
Seems it is shaft in shaft concept but not torsen.