MCoupé diffs... Torsen or NoTorsen??

[jaistanley]

OK.. Demlotcrew (Andrew) recently contacted me to make sure my claims that the MCoupé diffs are Torsen.

I have read repeatedly that they are, which made sense, so I assumed they were.

Now I have my doubts. He reports finding a clutch pack in his S54 engined Roadster/Coupé diff and I am yet to look inside mine.

It seems I may have fallen prey to the moronic idiots of t'interweb who have stated speculation as fact (hang on - me not included there!) and assumed it was. That or the american spec cars were different? Perhaps the MZ cars weren't equiped because of the extra thermal loading of the torsen type.

Can any of you beemer geeks somehow find out whats what with respect to Torsen type diffs on BMW's? I'd really like one to go with all that juicy power and had hoped I already had one from the MZRoadster I salvaged. Typical!

Jai

[Emotechnik]

None 'M' Z3's had the Torsen type LSD when the SA was ordered.

See link to my previous post.

http://www.e30zone.co.uk/modules.php?na ... highlight=

[Demlotcrew]

Have you looked inside yours yet?

Andrew

[jaistanley]

No dude.. It was peeing it down when I got home and I'm out on business this eve.

From what the boys over at s14.net have been saying there wasn't a torsen pre '98 on any beemer. Then the 2.8 and 2.8 Coupe (perhaps where confusion came from) plus any Z3 (non M) that came with a factory LSD upgrade.

The M diff in the Coupé and Roadster we have is a clutch type but with a higher torque capacity due to more plates. The lock-up is reputed to be the same (25%).

I'm considering selling mine and finding a 2.8 post 1998 diff. The Torsen type may do me real favours. If not, I'm happy that my M diff has a bit more guts than a STD E30M3 one as they are pretty strong units. To be honest I prefer the Idea of a Torsen diff to the racelogic traction control but at least with traction control you can set it to 0% slip when tired/snowy/rainy etc. We shall see.

Jai

[Demlotcrew]

Im confused, because if the Torsen is so good why did BMW not fit it to the ///M ? I think there might be a major catch somewhere.

Andrew

[Demlotcrew]

I know what the problem is! They will not work if one wheel is off the floor! Which means they are cack for track/race application.

Andrew

[Emotechnik]

Have you looked inside yours yet?

Andrew

Yep, definately a Torsen, was from a none M Z3 roadster

[BMW_YARD]

The Torsen limited-slip differential is so much better in wet conditions than a pre-loaded LSD, the Torsen has no basic locking power, it's just like an 'open' diff, so no push on (understeer) or snap sideways (oversteer) the BMW specified the limited slip effect as 25%.

When you press on it'll lock up to 25%, but nice and progessively, not ideal for drifting, but if you like 'driving' it's very good.

04/98 was the first time it was used.

[Demlotcrew]

Yes in the Wet maybe,

But i for one dont push my car in the wet!

I bet when it comes down to dry days the clutch LSD shines.

I just cant see why BMW didnt fit it to the ///M if its so good.

[BMW_YARD]

What I mean by 'push' is the effect of a locked diff on the balance of a car in the wet when apexing a corner, a normal LSD in the wet, where clutch pack grip is relatively high in relation to tyre to road grip, makes driving shall we say more interesting.

It's far less heart-in mouth in the wet with a torsen.

Also torsen, can effectively without laod become an open diff, so it will work better with ASC+T.

Wheel slip > Engine power reduced > Diff goes open > rear brakes are able to be indivually regulated.

Individual rear brake modulation by the traction control system will be less effective across the axle of a car with a 25% locked diff.

In the dry the effective locking action of the Torsen is rated at 25%, so at full lock up it's equal to a plate type diff'.

This progressive nature makes it less easy to 'kick' the tail out.

[ste]

It's far less heart-in mouth in the wet with a torsen...

...This progressive nature makes it less easy to 'kick' the tail out.

[BMW_YARD]

No association, bit pricey, but if you want one, heres the link.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... %3AIT&rd=1

[Jhonno]

where on earth did the 13p come from?!

[jmc330i]

Question. Would the M roadster diff (3.15 is the ratio Id like) be any good for the S50 converted E30s if its a progressive LSD?

What would be the downsides?

[jaistanley]

It's not a Torsen unit dude... I have the 3.15 ratio LSD from an MRoadster for my swap, it came from the crash damaged car the engine was in.

I'd thought it was a torsen too.. In fact it's a plate type with more clutch pads to handle the torque I guess.

I'd like a Torsen unit, I might find out how much a second hand Z3 2.8/Z3 3.0 Torsen unit will cost. The MRoadster one I have must be worth something so I could sell it to pay for Torsen unit. Maybe a bit later as a handling upgrade..

People say that the diff will become open if a wheel lifts but E30's being RWD have their roll centre biased to the rear by setting the roll centre of the front suspension higher than that of the rear. This means that during cornering etc both rear wheels will remain on the ground, onlike a FWD car (think golf GTi lifting inside rear wheel). The chance of a wheel ever becoming totally unloaded are tiny. Also, in the wet for instance the wheel may be spinning but isn't unloaded. Only a small ammount of torque is required to load the teeth of the Torsen pack so they can do their job, that provided by the spinning wheel being enough allowing 0-100% of torque being applied to the opposite side.

EDL (I think ASC is BMW's way of saying electronic differential lock) is useful here to prevent one wheel spinning. When the system senses one wheel travelling x% faster than the other it applies the brakes allowing the diff to send the torque to the other side maintaining forward push.

I wonder how dificult it would be to fit the ABS and ASC system from an E36? Just need the loom from the E36, ABS sensors, ECU and pump I guess. Coupled with the Torsen I think it'd make for an interesting proposition in an E30. Probably a lot easier to drive in the wet/snow. I was considering Racelogic traction control for bad weather, but maybe the idea of using OEM parts is a good one.

Jai

[Demlotcrew]

Jai i would keep the ///M Coupe diff as anyone worth speaking to who race cars always take the clutch type LSD over the Torsen.

I would imagine that the Torsen pack is the same as this;

http://www.quaife.co.uk/products/atbdifferentials.htm

And not many people rate these now.

Andrew

[M3Compact]

The M diff in the Coupé and Roadster we have is a clutch type but with a higher torque capacity due to more plates. The lock-up is reputed to be the same (25%).

Interesting.

I've personally stripped a breadvan/M Coupe diff, it had a 2 plate ZF LSD unit as per E30, the only difference being that it mounts to the Crown wheel with 14mm bolts as opposed to the E30 12mm bolts. S14 block/head dowels enable the units to be mated with 12mm bolts. Afaik, E36 LSD units use 14mm, but I'm not sure about this.

I haven't seen a torsen diff on a BMW (other than the Quaife units), but I believe the 4X4 E30 and E34 use viscous LSD units.

[jmc330i]

I'd like a Torsen unit, I might find out how much a second hand Z3 2.8/Z3 3.0 Torsen unit will cost. The MRoadster one I have must be worth something so I could sell it to pay for Torsen unit. Maybe a bit later as a handling upgrade..

If you do decide to sell, let me know. I might be getting a 2.93 open diff for the time being but I want a 3.15 LSD, so I would be interested

[Demlotcrew]

The mcoupe is the better one to get, as it has stronger barings and can handle the 300bhp power of a S50.

Andrew

[jmc330i]

Are the Mcoupe and Mroadster diffs different then?

[Demlotcrew]

No they are the same, later ones are 3.15 the early ones are 3.25 but their construction is the same.

BTW the case is now different has more reinforcement castings.

Andrew

[Andy335Touring]

Will a Z3 diff bolt straight on with out any messing about like having to change the out put shaft hub thingys ?

[jaistanley]

Yea... I'm not too bummed about not having Torsen as the diff I have is pretty much garaunteed to get the power down for another 50,000 miles (It was specced that way from BMW eh?).

Clutch type LSD's are great for tail out action too, I was getting a bit paranoid after the ass out action I'm getting with 120 LBS/ft M42 torque (in the wet with rubbish tyres you understand). It's a touch ridiculous, I'm skating about but then I've sorted out the suspension and got RUBBISH mis-matched tyres for the very short term. (I'm a big advocate of good tyres)

Jai

[Demlotcrew]

Will a Z3 diff bolt straight on with out any messing about like having to change the out put shaft hub thingys ?

A normal Z3 one will yes! But a Mcoupe wont as it has mammoth half shafts!

Jai, don't bother with a torsen diff everyone I have asked said they are useless, all you need to do is hit a bump/stone and get a little amount of air and there's no LOCK! Its clear that BMW was aware of this and decided to fit a Clutch type Slipper on the Mcoupe. BMW must have tested the Traction control with the Torsen diff and I bet they found that the driver aid's included on the normal Z3's was just not quick enough to react and this must have unsettled the car on the road. I don't think it would be to bad on the track as there aren't many bumps/holes/stones to hit. But if one were to ride up on the rumble strips the wheels would get air.

Tis upto you mate!

What ever you do an LSD is a must! Today in the wet was just a total joy! I cant stress enough how important it is to not only have a LSD but one which has good lock! ITs night and day.

Andrew

[ian332isport]

Standard E30 LSD is more than strong enough to cope with an S50 engine. Mine has been going strong for over 4 years and is still silent. It's been to the Pod, the Ring and takes a good thrashing most days.

Ian.

[ste]

My Ring takes a good thrashing most days.

Ian.

[ian332isport]

My Ring takes a good thrashing most days.

Ian.

You around tomorrow ?

[ste]

I've got a meeting in London Village unfortunately. I should be about all the rest of the week though.

[ian332isport]

I've got a meeting in London Village unfortunately. I should be about all the rest of the week though.

Giz a shout on Wednesday or Thursday and I'll pop over

[Andy335Touring]

Cheers for the info Andrew, Z3 1.9 depending on the age come with either a 3.38 or a 3.45 i think which would be better than the 3.64LSD i've got now.

It gives me more options because the only E30 with a 3.46LSD is the 320 is which is very rare.

Ian, do you use the Z3M finned diff cover on your car ?

[ian332isport]

Ian, do you use the Z3M finned diff cover on your car ?

Nope

[Andy335Touring]

Ian, do you use the Z3M finned diff cover on your car ?

Nope

Cool, it's good to know your's is fine for all this time with out one, i'll save my money for some thing else

[ste]

I can recommend Beer.

[Andy335Touring]

I can recommend Beer.

Sounds good to me dude

[jaistanley]

Hmmmmm...

I have to replace the diff cover on the MCoupé diff I have (mount broke in accident) and was thinking about going in and buying a new one with bush already installed; now I'm not so sure. If it's a clutch type diff anyway I could just buy a second hand non-finned cover or fit the cover plate from the open diff thats currently in the 325i I have... correct? I'll replace the diff bush with an MCoupé one as I did with my 4.1 LSD, they're only 30 ish quid if I remember.

Just saved myself 100 quid (ish) by not getting the finned plate then.

Woohoo!

I still need an output flange (70 ish quid) and might aswell change the output seals at the same time (is this a hard job?)

Where do people get the oil for the diff? If I remember correctly it should be SAE90LS, is that right? Thats SAE90 oil to LS (LimitedSlip?) spec. When I got the oil from BMW last time they had no idea what was happenning with fluids. I had to take in a container to fill (fair enough) but I got the impression the little goit on the counter didn't even know what an LSD was, let alone which oil to use. Didn't inspire confidence! Diff seems OK so I guess he got it in the end, after nearly getting into a row over it.

Jai