S50 Swap from South Africa

[SAE30]

well, feel free to pop round and have a go at my rear wheels when the car is jacked up. They turn BOTH the SAME direction when you turn one wheel. So I must have a very special car, it drives when it actually shouldn't

And yes when I have only one wheel jacked up and one on the ground it is hard (but not impossible) to spin the wheel which is in the air. Keep in mind the OEM diff is only locking 25% and the preload is exactly measured like this.

The only thing I may be wrong is the fixed input shaft, might need to be loose

thats make more sense, in my understanding the only way (when fitted to the car) the input shaft would be locked is when the car is in gear, so in order to spin the wheels when locked , one would have to spin the wheels hard enough to turn the gearbox as well as the engine.....
is this understanding correct? sorry but not a real guru when it comes to diffs

[Gunni]

The only thing I may be wrong is the fixed input shaft, might need to be loose

I´m sure this is where the misunderstanding is coming from,

when the input shaft is free , the wheels do rotate the same way if they are both free.

[RoadHazard]

.... so in order to spin the wheels when locked , one would have to spin the wheels hard enough to turn the gearbox as well as the engine.....
is this understanding correct? sorry but not a real guru when it comes to diffs

Correct. This means you can still push the car when in gear, but it's very hard. This is how you can start your engine if you have bad battery or starter. And this method only works on the manual transmission.

[GeoffBob]

well, feel free to pop round and have a go at my rear wheels when the car is jacked up. They turn BOTH the SAME direction when you turn one wheel. So I must have a very special car, it drives when it actually shouldn't

With due respect Uwe, that's not a sensible argument for why you are right, that's just a dumb challenge. And no, your cars LSD is not special, I am sure it operates the same as any other I have worked on.

The only thing I may be wrong is the fixed input shaft, might need to be loose

Yes, I am sure that this is exactly the case. With the input shaft free to move you will observe both wheels turning in the same direction. In case it has gone unnoticed, my whole argument has been with regard to your statement about locking the input shaft.

[GeoffBob]

Seeing as we are on the subject of diffs... I keep posting this question, but no-one has been able to answer it, I think I can guess the answer though. Perhaps the clever bods haven't seen it.

Do they have the same 25% lock or 75% slip(depending which way you look at it) on coast and accel? Are the ramp angles the same? I suspect you could make noteable handling improvements(on a track) from chopping and changing the ramp angles. 40% accel lock sounds great on first impression, but this is likely to hinder you come corner time.

I have a tran X diff in my shed of a 205 and it is set for 35/65 giving me 65% locking force on acceleration and 35 % locking force on coast. I can change it to 45/45 and also change it to fully interleaved and lightweight giving different locking characteristics, harsh or less harsh.

I wonder if the BMW LSD has the ability to accept these changes with custom designed ramp angles or not? Obviously aftermarket stuff is there, but its seldem cheap.

Anyone know?

Jon, that certainly is an interesting question that you have posted, and that I must admit I have not seen on this forum yet as I am new here.

I would have to say that, in terms of the more common clutch type BMW LSD, the level of slip allowed will be identical on both acceleration and deceleration, and cannot be adjusted in order to provide more or less slip on one or the other.

This is due to the fact that the degree to which the sun gears are forced to engage the crown wheel via the clutch mechanism is a function of the axial force exerted upon them by the planet gears. Unfortunately, this axial force is regardless of the direction in which the planet gears are turning, and thus the level of slip will be the same both during acceleration and during deceleration.

The same is true of the less common viscous type LSD (although via a different mechanism that I won't go into here). However, with the more exotic electronically controlled diffs, what you have proposed is quite feasible.

I hope that this helps, and that I understood your question correctly.

[Gunni]

You can change the ramp angles on only one direction,
It was even discussed on this very forum, only ages ago.
Somebody with an E36 Compact used in Rally had been playing with changing ramp angles and what not.

[GeoffBob]

Theoritically, either open diff or LSD, BOTH should not allow wheels to rotate together when the input shaft is locked. If they do, something is probably broken. Nothing to do with the clutches though.

Thank you Roadhazard for this sensible post! I could not agree with you more if I tried.

As I kept saying over and over again in my earlier posts, and as you have just said, this action has nothing to do with the LSD clutch mechanism! It has, in fact, to do with the action of the planet and sun gears, which is common to both the LSD and open diffs.

The only action of the clutch mechanism is to bind the sun gears to the crown wheel in the event of slippage. That is to say when the planet wheels begin to rotate (about their own axes).

[GeoffBob]

You can change the ramp angles on only one direction,
It was even discussed on this very forum, only ages ago.
Somebody with an E36 Compact used in Rally had been playing with changing ramp angles and what not.

Gunni, can you explain how this is possible please since the planet gears are oblivious to the direction that they are turning in (and thus cannot tell the difference between acceleration and deceleration). I do not see how this is possible on a standard clutch type BMW LSD?

If this is in fact possible, I would certainly like to know how to do it.

[ian332isport]

I guess I was mistaken regarding the input being locked. It's been a while. I still maintain that an LSD will turn the opposite wheel in the same direction, and an open diff in the opposite direction.

Have a scan through this thread for info on changing the lock value.

http://www.e30zone.net/modules.php?name ... ramp+angle

Ian.

[UweM3]

Ok I stand corrected and had overlooked the fact that you wrote locked in 1st gear. How dumb I am.....

Maybe you should not have written so complicated and only mention once that the wheels indeed turn the same direction when the input shaft is free, I would have noticed my error earlier.

[GeoffBob]

... I still maintain that an LSD will turn the opposite wheel in the same direction, and an open diff in the opposite direction....

So long as the input shaft is free to turn, this is exactly what will be observed. Not to overemphasise, but my whole argument was with regard to the issue of locking the input shaft. I have no issue with regard to the wheels turning in the same direction, would be pretty difficult to drive the car if they didn't

Have a scan through this thread for info on changing the lock value.
http://www.e30zone.net/modules.php?name ... ramp+angle
Ian.

Thanks Ian, will do. I am familiar with how to adjust the percentage lock, but to the best of my understanding it is not possible to adjust the standard BMW clutch type LSD so that it presents one percentage lock under acceleration, and another percentage lock under deceleration. But if this is in fact possible, I am certainly interested to find out how.

Ok I stand corrected and had overlooked the fact that you wrote locked in 1st gear. How dumb I am.....

Maybe you should not have written so complicated and only mention once that the wheels indeed turn the same direction when the input shaft is free, I would have noticed my error earlier.

Sorry Uwe. I work in an industry where it is common practice to base ones argument on a solid technical foundation. I know of no other way to get my point across. I shall endeavour to keep my arguments simple in future. Your point is well taken.

[UweM3]

GeoffBob, that's one of the downsides of Internet. Face to face it would have been sorted in 2mins and all efforts could have gone into answering the question asked int he first place
Well I need to read better next time.....

[RoadHazard]

SAE30, do you have any pictures of your car showing clearance between the master cylinder and the plenum?

[SAE30]

SAE30, do you have any pictures of your car showing clearance between the master cylinder and the plenum?

not at the moment, i will take for you... i suppose u mean between the booster and the plenum?

[Jon_Bmw]

Thanks for the link Ian. I can't believe I have never seen that thread before.

As far as I understand it from that thread, you could modify the ramp angles to whatever you wanted. I'm suprised there isn't a market for the racers out there. I guess the difficultly comes on setting it all up. Doing a RWD looks particularly sad and makes my FWD one look tame!

I bet there are noticeable handling improvements by changing them up. The problem comes, a bit like going from worn out rubber bushes to polys, is that you'll be comparing a worn out slipper with a new one, albeit with different ratios. Getting the diff set up just right should help those with larger and heavier engines up front hopefully, whist being able to maintain good accel traction.

Sorry for clogging some of your thread SAE30, hopefully some of it(not my waffle) will be useful to you.

[RoadHazard]

i got a nice 3.15 LSD diff from a 323ti e36 compact. got it really cheap from the local yard, they really didnt know what they were selling

just 50usd

Is any modification required in order to fit that diff into an E30?

[GeoffBob]

Thanks for the link Ian. I can't believe I have never seen that thread before.

As far as I understand it from that thread, you could modify the ramp angles to whatever you wanted. I'm suprised there isn't a market for the racers out there. I guess the difficultly comes on setting it all up. Doing a RWD looks particularly sad and makes my FWD one look tame!

I bet there are noticeable handling improvements by changing them up. The problem comes, a bit like going from worn out rubber bushes to polys, is that you'll be comparing a worn out slipper with a new one, albeit with different ratios. Getting the diff set up just right should help those with larger and heavier engines up front hopefully, whist being able to maintain good accel traction.

Sorry for clogging some of your thread SAE30, hopefully some of it(not my waffle) will be useful to you.

Jon, help me out here please. I had a good look at that thread as well and understand the concept of changing the ramp angles (looks like a pretty easy job to machine). However, I still don't understand how this will change the degree of slip on acceleration compared to deceleration. Change the overall slip, sure. But change one compared to the other, I just don't get it?

This one area where I need clueing in and would appreciate an answer from someone please.

[Jon_Bmw]

I'm not your man! I'll see if I can dig out the destructions from my 205 LSD and see if it starts to slot in place. Having done one of my finals today, the chances of anything making sense are slim.

[SAE30]

Thanks for the link Ian. I can't believe I have never seen that thread before.

As far as I understand it from that thread, you could modify the ramp angles to whatever you wanted. I'm suprised there isn't a market for the racers out there. I guess the difficultly comes on setting it all up. Doing a RWD looks particularly sad and makes my FWD one look tame!

I bet there are noticeable handling improvements by changing them up. The problem comes, a bit like going from worn out rubber bushes to polys, is that you'll be comparing a worn out slipper with a new one, albeit with different ratios. Getting the diff set up just right should help those with larger and heavier engines up front hopefully, whist being able to maintain good accel traction.

Sorry for clogging some of your thread SAE30, hopefully some of it(not my waffle) will be useful to you.

dont stress, im sure this will help me and a lot of guys

[UweM3]

If my financial situation allows I will have the ramp angles modified as well. Just trying to get as much done as possible while the diff is apart. I also haven't decided on ratio. If I am going back to larger tyres a 3.25 diff will be too long. All depends on the clearance I can manage in the front wheel housing. (and I need a lot of room there to clear the tyres I would like to run)

[SAE30]

My diff is almost done, just waiting for the seals, i was a bit slow on the draw so my guy put in the 3.15 already and my heart was set on the 2.93, anyway i will try the 3.15 and keep the 2.93 ratios for the future...

[SAE30]

Diff is done but also managed to get one off a mz roadster so fitted that.....also 3.15..only thing is the back cover was broken and thats the looker on the diff, huge cooling fins, anyway i had to use my e30 cover...

had a problem where the heater pipes were rubbing against the intake, so shortened the alloy pipes and fed the rubber hoses inside , tight fit but all the better.
shortened and lipped



pipes

[SAE30]

Finally up and running, heres a short video clip....... small things to sort out....

[M3Compact]

Seeing as we are on the subject of diffs... I keep posting this question, but no-one has been able to answer it, I think I can guess the answer though. Perhaps the clever bods haven't seen it.

Do they have the same 25% lock or 75% slip(depending which way you look at it) on coast and accel? Are the ramp angles the same? I suspect you could make noteable handling improvements(on a track) from chopping and changing the ramp angles. 40% accel lock sounds great on first impression, but this is likely to hinder you come corner time.

I have a tran X diff in my shed of a 205 and it is set for 35/65 giving me 65% locking force on acceleration and 35 % locking force on coast. I can change it to 45/45 and also change it to fully interleaved and lightweight giving different locking characteristics, harsh or less harsh.

I wonder if the BMW LSD has the ability to accept these changes with custom designed ramp angles or not? Obviously aftermarket stuff is there, but its seldem cheap.

Anyone know?

Jon, that certainly is an interesting question that you have posted, and that I must admit I have not seen on this forum yet as I am new here.

I would have to say that, in terms of the more common clutch type BMW LSD, the level of slip allowed will be identical on both acceleration and deceleration, and cannot be adjusted in order to provide more or less slip on one or the other.

This is due to the fact that the degree to which the sun gears are forced to engage the crown wheel via the clutch mechanism is a function of the axial force exerted upon them by the planet gears. Unfortunately, this axial force is regardless of the direction in which the planet gears are turning, and thus the level of slip will be the same both during acceleration and during deceleration.

The forces are equal regardless of the direction Geoff, but the ramp angles control the 'leverage'.

Thanks for the link Ian. I can't believe I have never seen that thread before.

As far as I understand it from that thread, you could modify the ramp angles to whatever you wanted. I'm suprised there isn't a market for the racers out there. I guess the difficultly comes on setting it all up. Doing a RWD looks particularly sad and makes my FWD one look tame!

I bet there are noticeable handling improvements by changing them up. The problem comes, a bit like going from worn out rubber bushes to polys, is that you'll be comparing a worn out slipper with a new one, albeit with different ratios. Getting the diff set up just right should help those with larger and heavier engines up front hopefully, whist being able to maintain good accel traction.

Sorry for clogging some of your thread SAE30, hopefully some of it(not my waffle) will be useful to you.

Jon, help me out here please. I had a good look at that thread as well and understand the concept of changing the ramp angles (looks like a pretty easy job to machine). However, I still don't understand how this will change the degree of slip on acceleration compared to deceleration. Change the overall slip, sure. But change one compared to the other, I just don't get it?

This one area where I need clueing in and would appreciate an answer from someone please.

Using a shallower ramp allows the pin to climb the ramp more readily and applies the force to the clutches via the 'leverage' principle.

The pin tries to climb the ramp in opposite directions for power on & over run, which allows the unit locking characteristics to be directionally 'tuned'.

The pressure rings are harder than a goat's knee and are not easy to machine, spark erosion is generally the preferred weapon of choice.

It's extremely important to ensure that the pin sits at the same height in the pressure ring after machining, re machining the standard ramps lowers the pin height and the gears can foul. Therefore it's preferable to machine new ramps at 90 degrees from the standard ramps.

I have drawings for various ramp angle options if anybody requires them.

[GeoffBob]

Thanks for the answer Simon. I'd given up on anyone answering my question a long time ago. Much appreciated !!

Geoff

[Dave_M3]

Nice work on the Brake servo sandwich plate. Is it moved enough to avoid cutting the inlet plenum now?


Wouldn't mind seeing the 75% ramp angle drawings if you have them handy Simon

[SAE30]

Nice work on the Brake servo sandwich plate. Is it moved enough to avoid cutting the inlet plenum now?

thanks.... yes its moved quite a bit now, got alot of clearance, might be able to even use a bigger booster coz brakes not all that great at the moment.....

Still getting ROAD SPEED SENSOR fault.....