Stock bmw LSD 1 way or 1.5 ?

[ramzisleiman]

so i was wondering about the stock bmw LSD like M3's or E30 325's which came with an LSD.. or even the old E21 323. what kind of lsd is it ? Is it 1 way lsd or 1.5 way ?
what cars come with which?
thanks

[ramzisleiman]

anyone !!??

[Auraraptor]

IIRC it is a static lock 25% Salisbury unit.

http://www.tran-x.com/diffs/se.html

[Hoad]

They are 2 way

[ss109]

I prefer a 4-way, personally.

[epmedia]

80-83 E21 320is sport package cars have a 3.91 LSD 25%.
I'm not sure what you mean by 1/1.5 way?

[Hoad]

1 way, 2 way, and 1.5 way refer to the way the differential locks under acceleration and deceleration.

1 way means that the locking action happens just under acceleration while it operates as an open differential under deceleration. 2 way means that the differential locks the same way under acceleration and deceleration. 1.5 way means that the locking action under acceleration differs from the locking action under deceleration via different ramp angles.

Explanation of Ramp Angles

[epmedia]

Hoad - thanks.
That's an excellenent description and explanation.
I always wondered about these lsds myself.
Someday I'll figure out what the 25% means for the e21's. 25/75 maybe? .

Robert

[Hoad]

The 25% is the static lock up which is determined by clutch packs. So a differential with 2 clutch packs may have like 25% static lock and 3 clutch packs may have something like 60% lock, etc. Static lock is a sort of pre-load. If you were to change the ramp angle from say 60° to 40°, the amount of lock would increase; this is dynamic lock.

There's a lot of tuning that can be done the amount of static lock vs. dynamic lock. i.e. High static lock with a mild ramp vs. low static lock with an aggressive ramp.

xx/yy = xx° acceleration ramp angle, yy° deceleration ramp angle

[DKING 528e39]

ok so if i wanted my car to steer at a 90ish degree angle while heavy braking for a curve would i want a 1.5 way differential???

[Hoad]

If you want locking action on deceleration, you would need a 2 or 1.5 way. 2 way means the ramp angles are the same, 1.5 way the angles are different.

For a street car I would just get a 2 way diff like the standard M diffs. Anything more than that you would probably be racing on a track. There are many good threads on diffs in the track forum. Where do you think I learned most of this? (Thanks bf.c)

[Auraraptor]

Quaife's are effectively only 1 way, correct?

[ramzisleiman]

are u sure its 2 way in M cars ?.. is there any link or proof about that?.. i mean 2 way is almost like welding a diff right?.. driving an M car doesnt feel the same as a welded diff.

[Hoad]

Originally Posted by Auraraptor

Quaife's are effectively only 1 way, correct?

No, the 1 way, 2 way, 1.5 way refer to the Salisbury, clutch type diff. The Quaife is a mechanical torque biasing diff. Quaife ATB Differential

are u sure its 2 way in M cars ?.. is there any link or proof about that?.. i mean 2 way is almost like welding a diff right?.. driving an M car doesnt feel the same as a welded diff.

You are thinking of a spool. For example the E36 M3 I believe has 50/50 ramps. It is a 2 way. A spool, or welded diff, would be locked to where both wheels turn together and receive the same torque. Good for drag racing, not for road racing.

[Auraraptor]

Originally Posted by Hoad

No, the 1 way, 2 way, 1.5 way refer to the Salisbury, clutch type diff. The Quaife is a mechanical torque biasing diff. Quaife ATB Differential

I realize that, but given the Quaife uses a multiplier effect, it only really works when power is going to the wheels...hence is it an 'effective' 1 way or am I missing something.

[Hoad]

Yes the Quaife would be a 1 way. Not to many BMW road racers on this board use it, it's more useful on fwd vehicles. Courtesy of member =BA=:

The thing with the Quaife types is that they are not preloaded like the clutch types and need a difference in speed between the rear axles before they start working. If you go to WOT instantly it takes a bit of time before the diff reacts.

Also you don't have any lock on the deceleration side, which can be nice to have to stabilize the car under heavy braking (because the diff is locking the rear axles it's harder to lock up a wheel) The downside to this is that locking on deceleration can promote turn in understeer, that's where the assymetric ramps come in. You can set them to 45% acceleration and 25% deceleration for example. Quaife units do better in FWD applications because they have no need for locking under deceleration and create less understeer than you would have with a 2 way clutch type LSD.

That's why most prefer a clutch type on dry for a RWD application.

From this thread: Quaife now available for E46 non-M

[Auraraptor]

The lack of static does indeed make the cars much less prone to understeer on initial turn in.

The Q's also can take a huge beating...(I use Quaife's on 3 RWD high torque street cars)

[moroza]

Not sure about later ones, but early clutch-types are mild 1.5 way (1.2 way? ).

[ramzisleiman]

despite the fact that this thread already got a lot of useful info. my question is not yet to be answered!
to be more specific. an E28 535i / E12 535 / E21 323i / E30 325 almost all of those cars came with LSDs. What is the kind of that lsd! I am sure it is not a 2 way. is it 1 way ? meaning does the diff lock only when accelerating or is it 1.5 way ?..
Another question.. 2 way diffs are mostly used for drifting. Are they useful for drag too ?.. are they better than other kinds of diffs for drag ?..
thanks

[epmedia]

Hoad mentioned 2 way, I'm guessing newer model Ms.
Moroza mentioned 1.5 way for early models.
I'm gonna guess that my LSD came from a 80-83 sport model?
All I know is that both wheels spin in forward and reverse, so it's atleast 1.5?
And as far as I know, only Alpina, Sport, Winter Package, and M models came with LSD. I am sure there are some other motorsport companies that added custom LSD's as well.

So, I'm sort of curious like you now!
One of us may have to dig into one and find out for sure, cause I think there may be different setups based on the cars designed intentions (ie: alpina, sport, winter, M, etc.). Hmmm... I bet they may be all different?

Or maybe somebody will chime in and present all the "stock LSD facts" here.

Btw: the E21 LSDs have a big, sideways "S" on the rt side - that's all I really know about them. And the old Alpinas have a huge dual mount cover with big cooling fins.

Interesting topic. Robert

[ramzisleiman]

I was under my friend's car earlier today to check what might be written on his lsd! and i couldnt even find its ratio. where should it be written! the diff is really dirty. but i tried cleaning some dirt off it. where is the exact location and what does each number mean! any pix ?

[robmpulse]

Originally Posted by epmedia

And as far as I know, only Alpina, Sport, Winter Package, and M models came with LSD.

It came standard with those, but could be optioned without any of those packages or trim levels on most cars.....

[Hoad]

Originally Posted by ramzisleiman

despite the fact that this thread already got a lot of useful info. my question is not yet to be answered!
to be more specific. an E28 535i / E12 535 / E21 323i / E30 325 almost all of those cars came with LSDs. What is the kind of that lsd! I am sure it is not a 2 way. is it 1 way ? meaning does the diff lock only when accelerating or is it 1.5 way ?..
Another question.. 2 way diffs are mostly used for drifting. Are they useful for drag too ?.. are they better than other kinds of diffs for drag ?..
thanks

As far as I know only M cars and a few others came with LSD's. I know the E36 is a 2 way and I've heard that it has been that way for as long as BMW has put LSD's in street cars but I'm not 100% sure. The track forum would be very useful to you. They would also answer your drifting/drag questions.

[DKING 528e39]

whats the lsd on a e39 m3?

[Hoad]

Do you mean e39 M5? Probably the same as other M diffs, 2 way. For more info ask here- Track, Auto-X & Drag Racing Forum