Who is a LSD guru?

[pureboiracer 0]

Hey guys.

I want to get an LSD for my racecar. i currently have a small case 4.1 diff.

If i get a med case lsd can my 4.1 pinion and crown wheel fit into the med case with the lsd clutch pack?

and anyone have a rough estimate of what it would cost to do it if i sent it to a diff specialist?

[HELLBM 1557]

Kayne Barrie on 0274975330 (KBMotorsport). Dif specialist

[CamB 48]

Small case refers to the size of the case and the ring gear (168mm), so unfortunately it won't fit into a medium case.

http://www.metricmechanic.com/pdfs/metric-...ial-booklet.pdf

You need:

- an E30 or E28 medium case housing

- an E30 rear cover and E30 flanges

- a medium case LSD centre

- a 4.10 ring and pinion (can't recall from the top of my head where to find, but E34 520i rings a bell).

Obviously the first 3 can be found on an E30 LSD.

Glenn has posted where he had his swappage done, and a price for the simple job.

I have had Mal Clark at Bygone Autos (ph 09 483 3991) do mine. Mal can also arrange to have the ramp angles changed and extra clutches added, and I am sure others can too. Since I had all this done I don't know what simply changing over the R&P and setting the diff up correctly would cost.

(edit) Have vague recollection that a 4.10 LSD came on the M3s with overdrive gearboxes.

Edited May 20, 2009 by CamB

[conrod 1]

Kayne Barrie on 0274975330 (KBMotorsport). Dif specialist

+1

Kayne has prepared a lot of the LSD's in the BMW race cars (open class only! including mine) and I can't speak highly enough of his work. A very clever chap who won't rip you off. I believe that is who Mal Clark sends his diffs to as well.

The road car BMW LSD's are no good for track work, they are set up so soft you won't know you have one fitted.

For a seriously good upgrade he will machine the ramp angles to suit, machine extra clearance inside the housing for an extra set of clutch plates, set the whole thing up inside the housing and you will have an LSD that will last many seasons racing. He charges a fair price for an excellent job.

Conrad

[CamB 48]

Mal certainly outsources the machining of the ramp angles (Mal machines the LSD casing himself) and it may be Kayne who does that part.

[Guest FrantiC]

There was a guy in christchurch selling a 4.1 ring and pinion from an e30 m3 diff on trademe a while ago, Can't get on to check it at the mo if it's still on there though..

[mops 4]

or you can get a torsen centre... this thing is the shizzle...

[kerrynzl 3]

Lock it completely,

On a racecar you won't regret it [ all NZ V8's and V8 supercars etc are locked ]

You'll need to stiffen the rear "roll couple" a bit, because a locked rear will aggravate any existing understeer problems.

If you car has good corner entry, but loses a bit of drive on corner exit you need to stiffen the "rebound" on the rear shocks and soften the "jounce"

This helps the car turn in by unloading the inside rear but also helps the rear squat on exit [ weight transfer ]

Combine this with a locked rear is a recipe for fun!

[hybrid 1043]

Andy's open series e30 race car ran a locked diff for some of the season. Didnt work so well on sharper corners. Lost a lot of speed in the corners going sideways when others had traction, even with semi slicks. Great for launching at the start however.

[kerrynzl 3]

As I quoted before " a locked rear will aggravate any existing understeer problems."

Set up the car properly so it doesn't "push" or understeer. High speed corners can be remedied with shock absorber adjustments.

At low speed corners ,the rear roll couple needs to be stiffened

If the suspension stiffness is already correct for corner exit [ squat etc ] leave it as is , then add / or stiffen a rear "anti roll bar"

On slower tracks I used to soften the front "anti roll bar"

A LSD [ also ABS brakes ] are just a "quick fix" for a handling / traction problem.

pre-65 cars and HQ's run open diffs and they dial out the traction problems.In 1987 the "Leyton House" F1 team were qualifying with an open diff.

LSD's are a compromise for street cars [ LOCK IT UP ]

[pjay 8]

Kerry your last 2 posts have really seated with me. I love you man

I like doing skids , so my advice is " DON'T GET CAUGHT "

LSD's are a compromise for street cars [ LOCK IT UP ]

Edited May 26, 2009 by Pjay

[hybrid 1043]

LSD's are a compromise for street cars [ LOCK IT UP ]

Serious question here .. wouldn't a Qauife Torsen diff work better around tight corners than messing with the balance of the car just to fix diff issues ? I have driven andys old turbo with the Qauife in it and the car was seriously stable in the corners under loading due to the diffs split percentage drive to both rear wheels.

I'm talking outside of drifting here. I'm guessing your talking about drfit car setups ?

[kerrynzl 3]

Serious question here .. wouldn't a Qauife Torsen diff work better around tight corners than messing with the balance of the car just to fix diff issues ? I have driven andys old turbo with the Qauife in it and the car was seriously stable in the corners under loading due to the diffs split percentage drive to both rear wheels.

I'm talking outside of drifting here. I'm guessing your talking about drfit car setups ?

The answer here is a YES!

The Torsen Gleesen [ from TORque SENsing ] , And the crude ratchet "Detroit Locker" both unlock when the vehicle is in "over-run"

The Torsen doesn't technically lock or unlock and can't get more than 70% lockup. Torsens are also expensive $$$

The Detroit and the Locked rear are the only ones that get 100% lock up.

Any clutch type LSD requires a lot of pre-load on the clutches to work properly [ on a race car this pre-load can be so great that you are better off locking it completely ]

I have driven many cars with a Detroit Locker [ they make a noisy clunk when they lock ] but with a good handling car on the track they are silent!

Why? Because the "slip angle" of the tyres is greater than the differential between the inside and outside tyres.

On a bad handling car a detroit is noisy because it is "clunking in and out"all the time trying to recover lost traction

With a good budget I would go with the Torsen, but set the car up as if it didn't need it.

I am talking "Circuit Racing" here ! .......Drifting isn't racing [ it's entertaining though! ]

[CamB 48]

Kerry - are you sure all of that applies equally to independent rear suspension? I notice all the examples you've given are non-independent.

Re: the Quaife - Torsen style diffs not so good when you are on/off the throttle or under brakes (ie racing) compared to a clutch LSD.

[Mattzy 0]

I am talking "Circuit Racing" here ! .......Drifting isn't racing [ it's entertaining though! ]

Hey! Drift cars take the same racing lines, and barring suspension geometry / alignment (ok and aero in some cases) are nearly identical. You could take a top level drift car and make it a circuit car very easily... Vice-versa applies.

PS - Who the hell call's them detroit lockers? You quoting wikipedia or something?

edit/ ignore this... im special

One love.

Edited May 27, 2009 by Mattzy

[CamB 48]

PS - Who the hell call's them detroit lockers? You quoting wikipedia or something?

Detroit locker is different. Google it!

Presumably the best option for an E30 is whatever the factory did, due to unlimited budget leading to best alternative:

http://www.racecarsdirect.com/listing/2273...E30_75_LSD.html

Edited May 27, 2009 by CamB

[DRTDVL 0]

Kerry - are you sure all of that applies equally to independent rear suspension? I notice all the examples you've given are non-independent.

Re: the Quaife - Torsen style diffs not so good when you are on/off the throttle or under brakes (ie racing) compared to a clutch LSD.

I know a few rally guys that would disagree with that, over the corigation of rough surface roads, the cars (2wd) where getting very hard to control when one wheel would loose traction over a bump. One in particular change to a factory LSD diff and the car was quicker because it was more controlable... just to provide backing... the person mentioned had the quickes 2wd car at last years possum bourne rally...  

(link to car as it's for sale: http://www.trademe.co.nz/Trade-Me-Motors/S...n-209202033.htm - stupidly good deal... would have got this if it wasn't for the fact that i bought the pug one month previously)

[CamB 48]

Fair call - was meaning/thinking track rather than rally and generally forgetting about front wheel drive.

[pureboiracer 0]

i would lock it up but dont have the money to spend on new rear tyres every meet.

im not sure how a bmw would like a lock diff round the track though.

[Mattzy 0]

i would lock it up but dont have the money to spend on new rear tyres every meet.

im not sure how a bmw would like a lock diff round the track though.

New rear tyres every meet?!..Are you kidding? Welded diffs aren't that bad on tires.

I daily drove my last car with a locker for about a year and never had any unusual or rapid wear.

You are building a race car right?

and anyone have a rough estimate of what it would cost to do it if i sent it to a diff specialist?

To answer your question - Budget $1000 and your on track. I've just swapped an LSD into my E30 and replaced the bearings, machined some tighter shims.. And the end of it i'd spend just under the 1k mark including housing and LSD center, fluid, seals, blah blah...

Cam - My mistake on the detroit locker. Always learning huh!

[kerrynzl 3]

i would lock it up but dont have the money to spend on new rear tyres every meet.

im not sure how a bmw would like a lock diff round the track though.

Why would spend more on rear tyres if it is hooking up better , you wear tyres out more with the lack of traction [ ask the Drift boys about tyre wear ] If your car does better lap times the tyre wear will also increase

A detroit locker is a Ford patended component , I only used it as a comparison where you can actually "hear" it working

a detroit locker is also a good example of a diff that locks 100% [ like a welded rear ] but is open on over-run

Please don't take my comment about drifting as offending, this discussion is all about getting more traction and speed.

If I was to build a drift car I would lock the rear and set the suspension so the car is loose on corner entry [ it is a different game ]

Yes this does still apply to Independent suspension [ IRS has the added bonus of allignment adjustments ] semi trailing arms can sometimes be worse than a live axle

The [ simplified ] secret to oversteer / understeer is tuning the "roll couple" [ the ratio between front and rear roll stiffness ]

for example: a car could have a static weight of 60% on the rear wheels, but during cornering weight transfer [ bodyroll ] transmit 60% weight to the outside front because the front is stiffer and the chassis doesn't twist so it supports more weight

The laws of inertia are that the heaviest end [ at the tyre contact patch ] wants to keep travelling in a straight line. In this example the heaviest end is the front [ during bodyroll ] even though it weighs more on the rear on the scales

If you dialed in the springs correctly using either maths or "applied research" [ try it and see ] you would never know your car is locked except for corner exit speed and driving around in the pits

Hey Cam! Torsens are better with rough driving but you will still get 30% slippage [ they are mechanically impossible to lock up ]

Torsens are very simple to understand, they sense torque from the road so you can "turn in" under full throttle if you need to.

Detroits and Clutch LSD's sense torque from the 'engine'

[morerevsm3 7]

I rebuild my own, and change ramp angle for on power to 30*, leave power off at 45*

[hybrid 1043]

how do you find it at that ?

The e30 is running a standard 3.14 LSD from an m-coupe. with the standard m20b25 in it .. its pretty sh*t as I think the m20 just aint got enough power to lock up properly when needed? However once the s50b32 is in (what the diff is use too) it will be fine on the road for 'performance' driving .. and it being raced I'm expecting its not going to be a happy diff.

I talked to Kayne Barrie and he seemed to think that it would be fine for racing. Even on advice from others it wouldnt .. bit confused now as to what to do about it ...

Will deal with it when the time comes however I guess.

[morerevsm3 7]

standard they do not have enough lock up for track work, too easy to spin inside wheel, changing ramp angles means the more power you apply, the more lock you achieve in the diff

[CamB 48]

The diff in the M3 is funny - its the factory lockup (or lack of it). Don't get me wrong - its definitely an LSD but its pretty soft. Interestingly it locks up a little better if you're aggressive.

I'd had what morerevsm3 talks about done for my 2002 (lower ramp angle on acceleration side) - its was really aggressive on acceleration but less so on decel which assisted turn-in (although as Kerry notes there are other ways). I also had an extra clutch. It wasn't actually that tight, but with the ramp angles it engaged strongly. It was predictable and easy to drive. I'd love to get the same done for my M3 at some stage (for street).

That's about it for me ... I've reached the limit of my own knowledge. I've got a lot to learn about car setup (the next project for me once the car is running properly).

Edited May 27, 2009 by CamB