Z06 - I just love the single mass flywheels revs are great and h/t is much more fun and improved than before, and no i didnt tune and didnt know that i had to, Although i have a FVD tune, Rhonda didnt mention at all a re-tune for the single mass flywheel.

Matt - Would a layout of the track help you to determine what would be the optimal ramps for the LSD ?

 

GT-Silver,
The track is only one of several variables to consider when picking your ramp angles. Driver skill and driving style come into play as well. At the end of the day it's really a personal choice. However, the nice thing about going with our ramp kits are they are all dual cut outs. If you picked 50/80 and felt it was too aggressive you could back it off to 40/60 at later date. Nothing in setting up an LSD is set in stone. If it needs further adjustment or tuning it's "just" a matter of taking it back apart and putting it back together a different way.

 

This is a great write up with great pics in detail of the process! Thank you very much!

 

As some of you know (the ones patiently waiting to get their cars ready for the Spring track season. ) we were stocked out and back ordered on clutch kits for rebuilding LSDs for a couple of weeks. As of Monday we'll be flush again and anyone waiting to do this service is encouraged to drop me a line and get on the schedule. I've got a list of people that I've been calling and emailing, but if you didn't hear from me, please make sure you don't fall through the cracks and get in touch. We're hoping to be 100% caught up and back to our 24 hour turnaround goal by the end of next week.

Regards,

Matt

 

Matt on my 09 GT2 I have your 40/60 LSD and since I run Mosport 99% of the time I would like to try the 50/80.

What's needed for the conversion to 50/80, do I send LSD back to you?

 

Nope it doesn't need to come back to me. The 50/80 cut outs are already present on the cups if you want to have it swtiched over to the more aggressive rate. Up where you are I would take it to Speed Merchants/Kanata Ford or Fiorano Racing to have them switch if for you if you don't want to do it yourself. There's no reason for it to come back down across the border for me to reconfigure it.

Regards,

Matt

ps. For anyone who hasn't heard, we're back in stock on all service parts and rebuilding these things like they're rabbits breeding...

 

Matt, I recently read an article stating that putting an LSD in an AWD 996TT messes up the PSM. What has been your experience and feedback with this?

 

Have you got a link to the article?

 

Sorry it's been awhile and my memory isn't what it used to be.

I'm more interested in any feedback you may have received from your 996TT customers. Have they reported any PSM hiccups when a LSD was installed? I know that the PSM can be unplugged to completely disable it so I guess that would be the work around if there were any interference.

 

Larry,
It's not a complaint we've heard from our customers, and thus why I was interested in seeing the article and checking the credibility of the source...

 

hey matt,

amazing write up!!!
the best online-source i found so far concerning clutch type lsd stuff!

as i do track some 3-series bmw i would like to discuss on differences in lsd-setup due to other weight distribution and other power ratios!

i do have two 325i with ~200hp and front-engine/rwd of cource...
one is only for racing (the ring aka "nordschleife"), one for drifting events only.

i do have 4 lsd-equiped diffs at the moment for the 2 cars.
all are zf-type (size 006).

they are set to a conservative 25%/25% by bmw with 2 clutchpacks and preloaded with 50-70Nm with two cup springs. works for normal use...

i now drive a 45/45% with 60Nm preload in the racer via putting 2 more clutch packs in it and removing one cup spring. this setup was available from bmw motorsports just in this configuration!
works great so far, but maybe it still pushes a little to much when entering corners. but extremely stable on corner exits (as there comes no real power from the 325i engine )
opel had the same zf hardware but built it without preload (no cup spring) and zf suggests this as well in their general 4061-type lsd manual!
i now want to try a 75/75% lockup (via changing the ramps from 45° to 30°) and
a) completely remove the spring cups resulting in a breakaway torque of only <10Nm
or
b) installing a very weak cup spring for ~20-25Nm.

i guess, you would suggest to go with the b) version?!
or would you go with the a) version in this particular setup because of the few power and the according less heavy snap oversteer?

same thing for the drifter:
i want to change to 75/75% and would put some preload on it as i dont want the diff to suddenly open when i lift the gas during drifting, i.e. when sliding from one side to the other. i think, here it would make sense, when there is always a certain not to less lockup to always get a reliable locking. would 80-100Nm be enough or would you go even higher if only the drifting behaviour counts?

or is 75% generally to much lock for a low power 200hp car? is there a special relation between power and locking rate?

another question concerning porsche setups:
the 50/80 or 40/60 setups are always meaning the smaller lockup number for accellerating and the higher number for breaking?!
the reason for this is the special weight distribution (rear enginge, rwd) on 911 cars?
in the bmw world, it is generally common to drive the same ramp angles for push and pull. as i could have my pressure rings machined to any angle i want, would it make sense to try a 1.5way version? and if so, which way round? more lock on acc oder decel in the bmw?

 

and one more thing concerning wear of the cluch packs:
i heard from some people, that you have less wear with no preload. others say, if you have preload and the clutchdiscs therefore will never spin loose, you will have less wear?

my opinion is, you will have massive wear if your have really no preload at all and the clutchdiscs can really rotate "freely" (and therefore they wear as a inner tire does in an open diff car that has wheelspin when hitting the gas hard in tight corners).
you will also have wear if you go with really much preload as the clutches are pretty much engaged all the time. concerning wear the best way would also be your medium or at least a few preload?! am i right in that point?

 

as i cannot write a pn to matt, i have to bump this thread again...

 

The discs & plates in an LSD will only "slip" in direct proportion to the amount the wheels rotate at different speeds. So, no ... a low preload (or worn) LSD won't wildly slip its discs independent of the tires. (I've heard mechanics who should know better blame the LSD when it was obviously a slipping clutch.)

A high pre-load LSD can reduce wheelspin at low speeds, but if too highly preloaded could cause breakaway in wet/slippery conditions.

A low preload or zero preload LSD won't cause breakaway in the wet, but usually won't be as effective on deceleration.

Porsche has it pretty well figured out when balancing the disc material, # of discs, preload, and ramp angles.

 

Coes,
Sorry it took forever to get back to this thread. It's been a very busy Spring and while I mean no offense to you, I've had to focus on my customers who have been on my phone and in my email spending money and expecting me to ship parts to them quickly for their race season.

To be honest, I don't really have an answer to your questions on the ZF BMW set up. As I've indicated earlier in the thread there's a lot of debate and argument about the effects of preload versus ramp angles. Having zero direct experience with the BMW LSDs you are using I wouldn't only be guessing wildly since I don't have a clue what their ramp angles look like.

Though the question about the drifting car does contain a certain erroneous assumption. As you swing from one side to the other, the diff is not going to suddenly snap open on you and stop being locked. You are still going to be in conditions where you've got a significant difference in force and wheelspeed from side to side. While you will be going through the particular sequence of actions with throttle, brakes, and steering that will take you from drifting one way to drifting the other, the LSD is the last thing you need to worry about. Set it up aggressively. If I personally was building a drift car I'd just run a spool or welded diff. If 75% is the upper limit of what you can get out of your ZF LSD that's what you want for drifting.

As for the question of low preload or high preload causing more wear? As I believe Makua has tried to express, when you are driving in a straightline the plates aren't slipping against each other at all. The pinion spins the ring gear, which spins the output flanges and the wheels. It's only when you start to turn and introduce a difference in speed from the inside wheel and the outside wheel that the clutches will slip against each other. I think that the way that we set up the LSDs for most of you guys is the good balance point between wear and performance. I could put more preload in the LSDs, you would have more initial lock, and then you would have quicker wear, and if you want it to continue to work as well as it did when you you have to go in and periodically adjust the preload.

I am not a big fan of the no-low preload movement. Some people like it. I haven't seen those LSDs be terribly well performing in a track environment. And I think those of you who own one of Porsche's variants of that will agree with me given that you've experienced their performance firsthand. Results don't lie. When most of you pick up 2-3 seconds a lap at your home tracks after rebuilding with our differential internals, whether or not the low preload parts wear slow becomes irrelevant. They don't perform on the same level as the moderate preload and more aggressive discs do. People who modify and track their cars know and accept that there are tradeoffs in what they do. If you accept the position that the Porsche LSD actually works from day one then practically none of you who have done business with me have rebuilt your LSD because you wore it out. I personally don't think the LSD worked initially and while some people get marginal performance out of it and then see a drop off in effectiveness over time, to me Porsche just doesn't put enough LSD in the car to start with. You can say that it's a working LSD if you like, but it's not a very high performance one if you are going to consider it an LSD at all, and a high performance vehicle like a GT3 deserves a high performance LSD.

It's not like Porsche disagrees with me completely. If they did, they'd use the same LSD in their GT3 Cup Car that they use in the street GT3. But the Cup Car has a much more aggressive LSD. Porsche knows that more LSD is faster. Maybe eventually they'll build a somewhat more stout LSD for you guys who are buying new cars from the factory. In the meantime, we'll continue to support you with performance upgrades just like Moton does with suspensions and RSS does with trailling arms and solid bushings and the like.