Big LSD Shootout... OS Giken, Drexler, Titan, GKN, ZF...

[driftflo]

Originally Posted by gmd2003

Ha , I thought I got lock up reversed based on your previous reply this why I reversed myself . I'll stop answering until I get some sleep lol. At any rate the car puts the power down well mid corner and is very stable under breaking and controlled trail braking which was my goal .

hehe, yes. lsd setup discussion is something you should be well-rested ;-)

[gmd2003]

Originally Posted by driftflo

hehe, yes. lsd setup discussion is something you should be well-rested ;-)

Yeah post 24 hour call is not the time . I will ask Dan about my diff and let you know . I am curious now .

[1MOREMOD]

Does the partial lockup situations cause extra clutch wear since allowing clutches to slip? How frequently would a 3 clutch need to have new clutches?

[gmd2003]

Originally Posted by driftflo

hehe, yes. lsd setup discussion is something you should be well-rested ;-)

So it is a 30 % acc ramp and a 90% decel ramp with 85 lb/ft of preload with the clutches . Don't know where the 60 degree came from .
George

[driftflo]

Originally Posted by 1MOREMOD

Does the partial lockup situations cause extra clutch wear since allowing clutches to slip? How frequently would a 3 clutch need to have new clutches?

there are two kinds of friction in the lsd:
static (locked) and dynamic (wheels turn with different speeds)!

wear on the clutches is caused by dynamic friction. so whenever you drive a corner or the drivewheels rotate at different speeds the clutches wear.

the wear on a 3 clutchpack lsd is bigger than on a 4 clutchpack lsd.
how long you can drive with a certain setup depends on many factors: drivingstyle, which oil is used, how often ist the oil changed, what tyres are installed, what clucthes are installed (surface used i.e. sinter/moly/plain steel..., thickness of surface, ...)
and if you want maximum performance you won't wait until it is really worn but change it each season in a serious racecar, to be sure it has no performance drop. in a street car you can use it longer and live with a little drop in lockup capability and reaction times.

[driftflo]

Originally Posted by gmd2003

So it is a 30 % acc ramp and a 90% decel ramp with 85 lb/ft of preload with the clutches . Don't know where the 60 degree came from .
George

ok, now it makes more sense.

last question: 30 on accel and 90 on decel are the lockup percentages indeed? or the degrees of the according ramps?

because as i wrote above, 30% acc and 90% decel is a pretty "exclusive" setup for a FR trackcar like a M3/Z4... i know nobody else who builds or drives such a setup in these kind of cars. if the 90% decel lockup is true, you would have massive (!) turn in understeer! and on corner exit you will use only a small part of the torque available (especially on dry tarmac with sticky tires).

anyway: even this "strange" setup would already be an improvement over the stock unit.

[gmd2003]

Originally Posted by driftflo

ok, now it makes more sense.

last question: 30 on accel and 90 on decel are the lockup percentages indeed? or the degrees of the according ramps?

because as i wrote above, 30% acc and 90% decel is a pretty "exclusive" setup for a FR trackcar like a M3/Z4... i know nobody else who builds or drives such a setup in these kind of cars. if the 90% decel lockup is true, you would have massive (!) turn in understeer! and on corner exit you will use only a small part of the torque available (especially on dry tarmac with sticky tires).

anyway: even this "strange" setup would already be an improvement over the stock unit.

Degrees of the ramps . It definitely doesn't have turn in understeer .

[driftflo]

ok, so if you have 30° on power and 90° coast with 3 clutchpacks this results in the following lockup rates: 55-60% on power and 0% (open) on coast!
so you are right, there is no turn in understeer as it is completely open in that moment. this is a beginners street setup especially if you drive with dsc-on. not too good for racing and dsc-off driving.

again, even this setup is way better than the stock unit but far from a performance-oriented trackracing setup.

[bigjae1976]

Originally Posted by driftflo

and if you want maximum performance you won't wait until it is really worn but change it each season in a serious racecar, to be sure it has no performance drop. in a street car you can use it longer and live with a little drop in lockup capability and reaction times.

1MOREMOD is legit HPDE racer. He'll be changing those clutch packs out after every session!

[bigjae1976]

Originally Posted by driftflo

ok, so if you have 30° on power and 90° coast with 3 clutchpacks this results in the following lockup rates: 55-60% on power and 0% (open) on coast!
so you are right, there is no turn in understeer as it is completely open in that moment. this is a beginners street setup especially if you drive with dsc-on. not too good for racing and dsc-off driving.

again, even this setup is way better than the stock unit but far from a performance-oriented trackracing setup.

So I guessed that lockup on decel is bad...but I guess its good? When I think decel, I think corner entry to the apex. Locking the axles to xx%...doesn't that cause the rear end to not want to rotate?

This diff stuff hurt my brain but I like it!

[driftflo]

Originally Posted by bigjae1976

So I guessed that lockup on decel is bad...but I guess its good? When I think decel, I think corner entry to the apex. Locking the axles to xx%...doesn't that cause the rear end to not want to rotate?

yes, this is true. too much lockup on decel means it has some turn-in understeer. but bevor turning in there normally is a certain need to brake hard. and if you do that (especially in a quick corner, where you cannot brake on a straight line) the rear end gets nervous and wants to spin the car. therefore you have the decel lockup that helps keep the car straight and stable under hard braking. if you have dsc switched on or dont brake hard anyway you don't need decel lockup. if you drive and brake hard on quick racetracks, you definitely do need it to be quick!

turn in understeer then has to be reduced via other setup parameters (coilovers, swaybars, camber, square tire setup, ...).

Originally Posted by bigjae1976

This diff stuff hurt my brain but I like it!

yes, it is really difficult to really understand that stuff. there are very few out there who really have understood it ;-)

[1MOREMOD]

Originally Posted by bigjae1976

1MOREMOD is legit HPDE racer. He'll be changing those clutch packs out after every session!

Damn straight. How long will this take in the pits.

[1MOREMOD]

I guess the real question is how do you pick a set up that works for you. No reason for me to go drop 4k on a new differential that makes it harder to drive my car. It should make it easier to go fast or its worthless. Contrary to the jokes I want to put it in and be done. I don't want to have to mess with it to be faster than a beat stock lsd.

[driftflo]

Originally Posted by 1MOREMOD

I guess the real question is how do you pick a set up that works for you. No reason for me to go drop 4k on a new differential that makes it harder to drive my car. It should make it easier to go fast or its worthless.

go to someone you thrust and you are convinced he knows enough about lsd setup so that he can build a setup for you that fits your needs and helps you improving laptimes.

if someone sells a lsd for a bmw racecar, that is completely open on decel, i would avoid this vendor and search for another.

if you read this thread completely you will know more about lsd setup than most other people out there. so you can possibly judge for yourself if a suggested setup could be ok for you or not. if you are unsure, drop me a line with the suggested setup and i can tell you what i think about it.

and finally, if you think of importing a lsd core from europe, i can offer you a custom built unit that fits your needs.

[bigjae1976]

Originally Posted by driftflo

yes, this is true. too much lockup on decel means it has some turn-in understeer. but bevor turning in there normally is a certain need to brake hard. and if you do that (especially in a quick corner, where you cannot brake on a straight line) the rear end gets nervous and wants to spin the car. therefore you have the decel lockup that helps keep the car straight and stable under hard braking. if you have dsc switched on or dont brake hard anyway you don't need decel lockup. if you drive and brake hard on quick racetracks, you definitely do need it to be quick!

turn in understeer then has to be reduced via other setup parameters (coilovers, swaybars, camber, square tire setup, ...).

yes, it is really difficult to really understand that stuff. there are very few out there who really have understood it ;-)

Awesome info! I do appreciate your expertise!

[1MOREMOD]

Originally Posted by bigjae1976

Awesome info! I do appreciate your expertise!

+1 thanks for the help. me and james are looking at similar upgrades in the next year. i also need to decide between 3.91 and 4.10s. i was set on 3.91 after doing the math for my 2 local tracks but am unsure now. dont want to add extra shifts which would likely slow me down a bit rather than help.

[driftflo]

i am driving a 4.10 fd in my e46:
http://www.m3racing.de/e46umbau.html#20

but the ratio really depends on the track(s) you are driving. if you calculated that a 3.91 would be best, give it a try. the e46 definitely has a too long stock fd of 3.62. compared to the e92 6mt which has nearly the same gear ratios 1-6 and has a 3.85 fd although having more power and torque output.
although for a track-e92 i would also opt for a 4.10 (or 3.62 for the dkg, that has 3.15 in stock version).

[bigjae1976]

Originally Posted by driftflo

go to someone you thrust and you are convinced he knows

How did you know he liked to thrust guys?

I figured out a 4.10 on the tracks I used to drive would only become an issue in 2 turns...maybe. Otherwise the extra 600 rpms would help in a couple of places where I'm in between lugging the car around in 4th or going into 3rd for 2-3 seconds.

[1MOREMOD]

Originally Posted by bigjae1976

How did you know he liked to thrust guys?

I figured out a 4.10 on the tracks I used to drive would only become an issue in 2 turns...maybe. Otherwise the extra 600 rpms would help in a couple of places where I'm in between lugging the car around in 4th or going into 3rd for 2-3 seconds.

Just you buddy

[tikamak]

Originally Posted by driftflo

i am driving a 4.10 fd in my e46:
http://www.m3racing.de/e46umbau.html#20

but the ratio really depends on the track(s) you are driving. if you calculated that a 3.91 would be best, give it a try. the e46 definitely has a too long stock fd of 3.62. compared to the e92 6mt which has nearly the same gear ratios 1-6 and has a 3.85 fd although having more power and torque output.
although for a track-e92 i would also opt for a 4.10 (or 3.62 for the dkg, that has 3.15 in stock version).

Does the e34 m5 LSD and the E39 M5 have the same LSD internals apart from the 12 mm holes vs 14 mm holes on the LSD casing connection bolt to the ring gears ?

[driftflo]

yes

[tikamak]

Originally Posted by driftflo

yes

I think I will get a 750iL diff and open it and start this journey rebuilding the LSD inside it to put it in my Z4M.

I just would like to learn this. If it doesn't work out i'll a few hundred bucks at a loss.

According to your answer, I can get the 210mm LSD from the E34/E32 they are the same as the E39 M5 unit that diffsonline use. i will be getting some 14mm to 12mm rings and using my 3.62 stock gears. (edit: actually i will have to use the 3.64 gears that came with the diff)

I wish i could have found an E34 M5 diff pre 1994, it would have came with a 3.91