LSD Questions

[911-32]

I am looking at a clutch type LSD from one of the usual suspects.

It is described as a "set free LSD with 5 clutch packs per side, oversized roughly 20% over the factory clutch discs". Further described as "1.5 way, which locks up 100% on acceleration and 50% on decel". I have questioned this as I thought it was usually the other way around - like 40% on accel and 60% on decel on the factory cars with assymetric lock-up.

In response to the questioning, I was told it was up to 100% on accel and up to 50% on decel. So I guess I could set it up 40% accel and 50% decel to get close to the later factory set-ups (if in fact that is a desirable thing - I don't know)

So the question is, what is the "right" or recommended setup? My car is an 89 3.2 track car with most of the usual track day mods - suspension, brakes, some lightweight and more hp. Its reason for living is track days though I use the car on occasion for fun drives and will even take my 3 year old daughter to the supermarket in it if the mood takes me.

Any thoughts are welcomed.

RB

[Grady Clay]

RB,

Search on my name and LSD. There have been several spirited threads on this subject.

For track use I don’t like a LSD that releases when you transition from trailing throttle to acceleration. Usually that is just when you want the most predictable traction and balance. If you select the clutch discs to maximize the static break-away torque, that is about the best you can do to minimize the issue.

I use a spool (welded open differential) for the track. That of course is totally unacceptable for the street. After the event I even undo one axle so I can drive (or push) easily in the paddock or loading.

Best,
Grady

[Bill Verburg]

The asymmetric LSD are generally setup as you describe less on acceleration/more on deceleration. Ratios from 20/40 to 20/100 have been offered on various models. For general road use and DE 40/60 or 50/70 seem to be most popular.

The better(for sporting use) LSD will have 2 friction discs on each side and either 2 or 3 outer plates that create the friction surfaces

The older symmetric 40% LSD had 2 friction disks, 2 outer disks w/ essentially 2 frictions surfaces. The 80% LSD had 2 friction disks, 3 outer plates(the third one between the 2 friction disks) and 4 friction surfaces. There is also a mechanical preload. Breakaway force for the 40% is 29-58lbs.

Starting around '84 and going up their all the 993s anyway the 40%, 22/40, 25/60 et al had 1 friction disk per side, 2 outer discs, 2 friction surfaces but only ~7-25 lbs break away(not good for sporting use)

The 964 and 993 motorsport diffs have 2 friction disks per side 3 outer disks per side 4 friction surfaces and the additional asymmetric lockup feature but alwayd more on deceleration than acceleration. I suppose the ramps providing asymmetric lockup can be be reversed to provide the opposite ratios.

It sounds as if the vender is confused and means 2 friction/3 outer plates per side, and probobaly 50/100 acc/decel.

[911-32]

Its Powerhaus. They should know what they are doing/talking about, right?

[911-32]

I am on the phone with them (on hold while they check with the techs). They swear its 100% on accel and 50% on decel. Its a full race diff and they reckon its the real deal - and that GT's diffs work the same way.

They can adjust it down to 60% on accel, no problem so thats what I am going to to do.

RB

[Bill Verburg]

Originally posted by 911-32
Its Powerhaus. They should know what they are doing/talking about, right?

One hopes so

[Bill Verburg]

Is this a factory unit(ZF or GKN)? Or a Guard(GT) unit?
also this is for a G50 correct?

[drsimonwong]

Hi,

It's a KAAS unit. Lots cheaper than a Guard unit. Asymmetric with higher lockup on acceleration. Configurable to 100/60 or 60/30.

Japanese and designed for WRX's and Evos which are 4WD and have different characteristics to our rear engined cars.

This is my previous link:
60/30 lsd question

Simon