S54 advice and considerations

[Wanganstyle]

I was led to believe the 3.23s were torsen

Who knows. Some z3 supposed to have torsens end up equipped from the factory as clutch units. Best to actually look inside the diff

With an awd car + trackwork a clutch LSD rear set high locking @ 1.5 or 2.0 way would be the ticket for lift throttle/ turn in / smack throttle corner entry/exits.

[e30polak]

Wangan, the Z3 Mcoupe LSD unit is definitely different/better than the e30/e24/e28 units.

[gobuffs]

Wangan, the Z3 Mcoupe LSD unit is definitely different/better than the e30/e24/e28 units.

That was my understanding too, but an M coupe owner that is much more knowledgeable than me says it is hit or miss and mostly miss with the torsen. It was heavily advertised when the M coupe came out but it appears that they really have a clutch pack diff.

[Jason89i]

I've had the 3.15, 3.23, 3.46 and 3.64 behind my s54/zf5. my preference: 3.46 for the street, 3.64 for the track. J

[Wanganstyle]

Wangan, the Z3 Mcoupe LSD unit is definitely different/better than the e30/e24/e28 units.

WHAT do you feel is "better" about the Z3m diff unit besides the trendy cover?


better? I Disagree;


I don't think one can objectively make blanket statements just because an item costs more or is from an obscure model. Espically if the "why its better" is unknown.

IMO even the most interesting/special Z3m LSD unit is slightly DE-TUNED in comparison to any plane jane E30 LSD; its LESS Aggressive in many ways

teardown /internal Photos of all styles of LSD were posted on this forum quite some time ago...........

It (z3m and z3 in general) is different somewhat and sometimes; internal specification varies. BMW used Z3 chassis as a very weird test bed; usa production - not a german built thing. Very strange test in many chassis dynamics, power train combos. Small enough build to make weird bastard children configs!

the guts in any Z3m LSD (torsen or clutch type) have not much locking when airborn.
IF it happens to it will have be fitted with a standard 188mm e36 LSD unit, and those are not any better than any e30 unit.

the Z3 clutch units are in both standard e36 style and funky experimental style.

Funky units are actually configured in an archaic Alpha Romero (circa 1970's) style, have no/very little locking when one wheel is airborne - come drive a big boy track like Infineon or Laguna and you will see this show its ugly head. If you find my thread with photos of the guts, internal stacking config then perhaps you would understand. IF you actually go through the internals of a decent amount of them you will find some strange variations as well to the funky config.

What are these specifics? Find out by building it.

Perhaps its my rally background showing, but LSD is a custom affair. LSD NEEDS TUNING


Built Not Bought.

The aptitude and performance level of tuning of many non-track performance based tuners shows HUGE when otherwise decently equipped cars just run random secondhand rear diff/ with stock configuration and expect it to "be good".

this is the R3V way of doing things. :weak::weak::weak::weak:

Many R3V'ers just wish to have a giant monster mod list and 24v swap to show off- Where is the high performance Chassis innovation, Driveline innovation and efficiency to create better more innovating E30's???

Just something I have noticed. many spend 2-3-4-8k easy on some marginal 20% hp increase, hours and hours rebuilding sub part 24v engines. BUT nobody really cares to tune or understand diffs- and this is the FINAL DRIVE to the GROUND. Only more determining factor of driveline tuning than diff is TIRES. One building an e30 could easily call Jim Blaton, Performance gearing, Dan @ DOL, and just order a unit built if desiring a higher level of tuning.

Most of the higher performance Japanese cars getting actually tuned are not even bothering with stock LSD because the owners are not broke/cheapasses. Even cheap garbage 240SX / drift/grip/track cars are fitting nice LSD units.

The m coupe LSD u speak of in either clutch config or torsen would put down SLOWER lap times on the mountain or track if installed in the typical modified E30 - YOURS with S54 would be included...

try it, tell me about it.

Seemingly people are afraid of really modifying how the car handles; LSD is the only analog chassis dynamics weapon a 2WD chassis platform can easily tune and customize.


Z3's including m's actually had 3+ different diff internals from the factory. In many ways the common e30 LSD is an upgrade item. I am talking clutch LSD center unit vs clutch; Torsen is a different beast.

A gear type diff handles completely different than any clutch style. Torsen in an e30 is great handling (in my experience- I fit one 2 months earlier in year in my e30;

Torsen was my baseline for handling as it is most similar to an open: Least hampering of true traction line, only 100% consistent torque transfer diff you can choose; transitions cleaner than with a clutch LSD (IMO)

1. Open diff
2. Torsen-2 way clutch
3. 1.5 way clutch now.

The chassis is fastest with a high locking 1.5 tight or 2.0 way clutch unit (IMO). "fastest" to the nut behind the wheel. There is a reason that track weapons and OEM BMW motorsports spec Clutch LSD units - NOT the street units; Aftermarket BMW Motorsports unit.

the Z3m funky unit can be built up for high performance yes, but that requires a full build / recofig and fresh EVERYTHING - same effort/labor for a high output e30 OEM LSD result and I still feel a re-configured E30 325 whatever LSD cartridge would be better end product than a fully re-configured z3m funky unit.

Z3m diff is very tame setup from factory ON PURPOSE.

[gobuffs]

I doubt I'll ever get rid of my 4.10. :-) Although if I get faster I might need a 3.91 instead.

[Jason89i]

WHAT do you feel is "better" about the Z3m diff unit besides the trendy cover?


[B]better? I Disagree; ....................

Z3m diff is very tame setup from factory ON PURPOSE.

Agree. I had a mz3 torsion in my s54 powered car. worthless half the time. one wheel wonder exiting over bumpers. Skip that. Give me an e30 locker.

j

[nando]

Agree. I had a mz3 torsion in my s54 powered car. worthless half the time. one wheel wonder exiting over bumpers. Skip that. Give me an e30 locker.

j

good to know. for me the appeal of the MZ3 was low cost (if you can find one), direct fitment, and comes in the ratio I desire. I dunno about using a clutch type diff in my car.. and I don't really want to use a 250,000 mile VC diff as a base either.

[Wanganstyle]

good to know. for me the appeal of the MZ3 was low cost (if you can find one), direct fitment, and comes in the ratio I desire. I dunno about using a clutch type diff in my car.. and I don't really want to use a 250,000 mile VC diff as a base either.

Clutch rear LSD is THE preferred high performance rear LSD for awd vehicles; reference evolution's and STI's - both avail in rear bias and 50/50 settings, clutch is always spec'ed for the highest performance models.

Awd with rear bias with Torsen is nice untill you come across an uphill hair pin with large elevation gap. OR a turn like #5 or #6 @ Laguna with tricky berms

Then you will curse that you are not running a clutch pack style LSD.

[nando]

how about something intermediate like a 3 disk setup?

I saw some pretty sketchy "rebuilt" 40% lockup LSD's on ebay.. made with used parts, for over $600. yeah, right!

[Wanganstyle]

Street/milder setup track cars really dont need any more than 3 disc; a local track car (who drives it to the track) is running a 3 disc stock ramping angle 3.46-188mm paired with ls7 7.0L vorshlag setup, he is pretty happy, balanced item is key.

Usually many on a quest for higher locking setting items are way overboard for chassis/footwork/driver setting. Jean's 4 disc is paired with full race+R comps; without the R tires and if was a street car would be pretty disagreeable.

David is running secret++ super locking setup in his, but car is only for 1/4 mile (9.05 currently). His diff is set to go STRAIGHT. no turning for that car

Items like 90/10 asym or similar staggering LSD settings are very specific; may cause irritation in driver results as it may really not be your style.

Suggestion? Start easy, increase locking when needed; LSD TUNING is specific to the driver and car :)
Since you can build an engine and a DME from scratch, you can probably tune your own LSD!

[Wh33lhop]

Agree. I had a mz3 torsion in my s54 powered car. worthless half the time. one wheel wonder exiting over bumpers. Skip that. Give me an e30 locker.

j

Ready for some pedantry? ;) Torsen. TORque SENsing. :p

Street/milder setup track cars really dont need any more than 3 disc; a local track car (who drives it to the track) is running a 3 disc stock ramping angle 3.46-188mm paired with ls7 7.0L vorshlag setup, he is pretty happy, balanced item is key.

You know, it occurs to me that adding extra clutches, because of how they are added--since you do not increase frictional area--does not actually increase increase locking rate, just preload. They basically act as shims.

Rather, if you consider a locking force vs. torque curve, adding extra clutches does not increase the slope of the curve like extra ramp angle, it only shifts it up. So, ramp angle modification would possibly be a more streetable solution as it will lock up more at higher torque levels (when you are goosing it), and lock up less at lower torque levels (when you are driving normally).

[Wanganstyle]

Ready for some pedantry? ;) Torsen. TORque SENsing. :p



You know, it occurs to me that adding extra clutches, because of how they are added--since you do not increase frictional area--does not actually increase increase locking rate, just preload. They basically act as shims.

Rather, if you consider a locking force vs. torque curve, adding extra clutches does not increase the slope of the curve like extra ramp angle, it only shifts it up. So, ramp angle modification would possibly be a more streetable solution as it will lock up more at higher torque levels (when you are goosing it), and lock up less at lower torque levels (when you are driving normally).

the ramp angle def. affects the locking. i.e. 2 way ramp, 1.5 way ram (asym), the lower the angle slope the easier it is to lock up.

ramp angle modification locks clutches more/less when drive shaft/axel imputs change.

ONE can add more preload by adding preload- there is a part in the diff (bellvue spring) for adding preload. Adding preload can be done with THICKER clutches and thicker dogs, but adding more clutches requires removal of spacer - so if done, one does not add any more preload (unless more preload is requested and specifically added.).

no added preload is required when adding clutches, many are adding preload when DIY rebuilding diff's and not completely understanding the end product (more potential understeer)


one could even add additional clutches and DECREASE preload :)


BMW also has OEM 4 clutch LSD's that are UNLOADED -no preload, no bellvue spring. BMW Started doing this in small runs starting circa E3 / E9 era :)

Extra clutches adds MU by doubling surface area; just like a single/double/triple plate tilton for 1,000hp++ supra.

for Aftermarket (KAAZ, OSG, CUSCO) LSD units with many discs one can change the pairing from clutch/dog/clutch/dog to clutch/clutch/dog/dog pairing to DECREASE locking :)

More friction surface pairs = more reaction to locking - one can alter these characteristics by changing ramp angles, altering clutch/dog pairs, altering bellvue spacers (adding, changing spring rate, or removing entirely)

[LJ851]

the ramp angle def. affects the locking. i.e. 2 way ramp, 1.5 way ram (asym), the lower the angle slope the easier it is to lock up.

ramp angle modification locks clutches more/less when drive shaft/axel imputs change.

ONE can add more preload by adding preload- there is a part in the diff (bellvue spring) for adding preload. Adding preload can be done with THICKER clutches and thicker dogs, but adding more clutches requires removal of spacer - so if done, one does not add any more preload (unless more preload is requested and specifically added.).

no added preload is required when adding clutches, many are adding preload when DIY rebuilding diff's and not completely understanding the end product (more potential understeer)


one could even add additional clutches and DECREASE preload :)


BMW also has OEM 4 clutch LSD's that are UNLOADED -no preload, no bellvue spring. BMW Started doing this in small runs starting circa E3 / E9 era :)

Extra clutches adds MU by doubling surface area; just like a single/double/triple plate tilton for 1,000hp++ supra.

for Aftermarket (KAAZ, OSG, CUSCO) LSD units with many discs one can change the pairing from clutch/dog/clutch/dog to clutch/clutch/dog/dog pairing to DECREASE locking :)

More friction surface pairs = more reaction to locking - one can alter these characteristics by changing ramp angles, altering clutch/dog pairs, altering bellvue spacers (adding, changing spring rate, or removing entirely)

More pedantry? Bellvue is a city in Washington state and although they probably have a spring or two there, it is not in your diff.

A bellville spring (also known as a conical spring) is in your BMW clutch type LSD.

[The Dark Side of Will]

Ready for some pedantry? ;) Torsen. TORque SENsing. :p

You know, it occurs to me that adding extra clutches, because of how they are added--since you do not increase frictional area--does not actually increase increase locking rate, just preload. They basically act as shims.

Rather, if you consider a locking force vs. torque curve, adding extra clutches does not increase the slope of the curve like extra ramp angle, it only shifts it up. So, ramp angle modification would possibly be a more streetable solution as it will lock up more at higher torque levels (when you are goosing it), and lock up less at lower torque levels (when you are driving normally).

Thanks! I was thinking I was going to have to be the ass who points out what Torsen is... ;)

Like Wanganstyle said, changing the number of clutch disks changes the relationship of locking torque to clamp load on the disks.
IE, (pulling numbers out of the air) a 45 degree ramp with a 2 plate clutch pack might deliver 200 ftlbs of locking torque at a given driveshaft torque. The Bellville spring might give it 50 ftlbs of locking torque from preload.
The same ramp with a 4 plate clutch would deliver 400 ftlbs of locking torque at the same driveshaft torque. The same bellville spring in the 4 plate unit would have 100 ftlbs of locking torque from preload, BUT using a softer bellville spring can drop the 4 plate unit back down to 50 ftlbs.

So the number of disks *DOES* affect the slope of the locking torque vs drive torque curve.
LJ851 posted while I was writing, but I already knew what a bellville spring is ;)