How does diff type (RWD-open, welded, 1,1.5,2 way) affect turn-in?

[handfulz28]

Perhaps this is a two-parter because I don't know exactly what makes a differential 1-way, 1.5 way, or 2-way. Right now I've got an open diff, OEM viscous limited slip, a Quaiffe and an OEM zexel-torsen type. It's been a long time since I've run with the open diff and the car is completely different now. But I have run the Quaiffe the most, and I have one weekend on the viscous. Of course each different type has a different ratio so I'm not sure how that plays into it.
The reason I ask is because with the Quaiffe the car turns in under braking very easily. But with the OEM-viscous it didn't want to turn in nearly as well. I haven't run the OEM gear-type diff yet.
My particular platform is an ITA 240sx but I imagine the info will apply across RWD cars? Thanks for any insight for this diff-newbie...
Good luck have fun,
Michael

 

[BMW RACER]

Here's what I've noticed, tried various diffs, mainly on BMW's.

Open: Turns in great, but obviously puts all the power to the wheel with the least traction. NOT GOOD.

Quiaffe: Turns in great, puts power down great, provided the inside wheel is loaded, if it lifts for any reason it reverts back to open. NOT SO GOOD

Welded: Pushes on the way in, loose on the exit. Not perfect but consistant and cheap! Plus you can get more aggressive on corner entry (less trailing throttle oversteer)

Clutch type: Turns in well and puts power down well. This is my prefered diff.

Having said that, I tried all of the above on my old 2002 ITB car and came back to the welded diff! I tried welded vs clutch type on my E30 ITS car and chose the clutch. My current E36 ITS car has allways run the clutch type.

Also when we ran the 240sx's in Speedvision we ran the viscus and they worked well too.

That's not even my two cents!

Cheers.

 

[Dyno]

Turning requires the inner wheel to either
a.) rotate slower than the outer or
b.) skid.

Obviously, it's easier to do "a" if you can. Therefore, a car with an open diff will turn in easier and freer than a car with a welded diff. Just try to push a live-axle go-kart around in a circle and you will see what I mean.

Remember; "differential" referes to a device that permits differential wheel speeds. I guess that makes "welded differential" an oxymoron, eh?

A clutch-type LSD has preload, meaning that it takes a certain amount of force to cause the wheels to spin at different speeds. This puts it toward the "welded" end of the spectrum as far as turn-in in concerned.

On the other hand, Quaiffe-type diffs require very little effort to achieve different wheel speeds as long as you're off-throttle, meaning they are toward the "open" end of the spectrum.

Viscous diffs are somewhere between the other two in terms of force required to cause the wheels to rotate at different speeds.

That's the theory, anyway. I think you two guys have very well-calibrated butts to pick this up so clearly from behind the wheel.

 

[seckerich]

To add to some very good information the clutch type will act very different based on preload and ramp angles to the clutches. Can be made to act open off power and still lock hard on exit.