Basic 915 LSD question

[daepp]

Can anyone explain the difference in a 40% vs. 80% LSD? This has been suggested for a race-setup 911. How would this handle around town - would it still handle around 90 deg corners?

Admittedly, I know very little about limited slip diffs.

[Bill Verburg]

Originally Posted by daepp

Can anyone explain the difference in a 40% vs. 80% LSD? This has been suggested for a race-setup 911. How would this handle around town - would it still handle around 90 deg corners?

Admittedly, I know very little about limited slip diffs.

Through ~'83 the ZF 40% and the 80% are the same diff. They get different locking % by stacking the drive and driven disks differently. Additionally the limited slip break away torque can be adjusted by altering the preload on the assembled disk stacks.

JMO but for a dual use car, stay w/ 40% and don't go crazy on the preload. For a track car only 80% will be ok, but tight turns in the pits and really slippery track)think covered in oil or coolant) can be an issue.

[Peter Zimmermann]

As Bill said...

For my E/P SCCA car (914) we used 80% for short tracks (Carlsbad Raceway, Phoenix Firebird, etc.), and for long tracks (Willow Springs, Riverside, etc.) we used 40%. I felt that 80% provided point & squirt performance exiting slower corners, while 40% gave me a very balanced high speed car with no surprises. I used 40% in my PCA Club Race 911SC, I think that 80% is better suited to drivers who like an oversteer condition (I don't).

[daepp]

CAn you tell me what the % numbers represent. Is it an amount of slip?Is it a ratio of one side to the other with respect to rotation?

[Geary]

Porsche calls it: "Percentage of anti-slip effectiveness" ...

[daepp]

So is a standard differential zero %?

[Geary]

Yes, an open diff is 0%.