Blackline helical LSD - any good?

[GuidoK]

I was referring to the more powerful turbo charged E89s..I would have thought with the substantial mid range torque of those newer generation turbo charged engines that a LSD would have been a useful addition to help what appears to be the documented way would behaviour of the more powerful versions?

Z4's are pretty much parts bin cars. As the e89 rear axle is very much based on the e83 X3 rear axle, for that platform there is no LSD available in the bmw parts bin. Therefore no LSD for the E89 (factory fitted that is). Just like there is no factory fitted lsd for the non M e85 platform (e46 based).
The Z3 has been fitted with lsd's as that uses a modified e30/e36compact rear axle. Lots of LSD's for that rear axle achitecture.
Sourcing an external supplier to develop an lsd and factory fit it is generally way to expensive, certainly for the Z type cars as their salesnumbers are dwarfed by the other models.

[Ed.Straker]

I was referring to the more powerful turbo charged E89s..I would have thought with the substantial mid range torque of those newer generation turbo charged engines that a LSD would have been a useful addition to help what appears to be the documented way would behaviour of the more powerful versions?

Z4's are pretty much parts bin cars. As the e89 rear axle is very much based on the e83 X3 rear axle, for that platform there is no LSD available in the bmw parts bin. Therefore no LSD for the E89 (factory fitted that is). Just like there is no factory fitted lsd for the non M e85 platform (e46 based).
The Z3 has been fitted with lsd's as that uses a modified e30/e36compact rear axle. Lots of LSD's for that rear axle achitecture.
Sourcing an external supplier to develop an lsd and factory fit it is generally way to expensive, certainly for the Z type cars as their salesnumbers are dwarfed by the other models.

Thanks for the insight

[abar121]

Thanks for the interesting analysis. Any idea how a Wavetrack LSD would compare?

The Z4M remains the most powerful Z4 produced, if only on paper The LSD is put to good use in this weather!

[mmm-five]

Thanks for the interesting analysis. Any idea how a Wavetrack LSD would compare?

The Z4M remains the most powerful Z4 produced, if only on paper The LSD is put to good use in this weather!

Only in horsepower. The turbo models usually have a lot more torque though (e.g. the 35is/40i have about 100lb/ft more than a Z4M) - which is where an LSD would help putting the power down.

[GuidoK]

Only in horsepower. The turbo models usually have a lot more torque though (e.g. the 35is/40i have about 100lb/ft more than a Z4M) - which is where an LSD would help putting the power down.

It's lb.ft, not lb/ft
the engine torque itself is not really an issue. It's wheeltorque that breaks traction, not enginetorque. So gear ratio's have to be taken into account.
Just the difference in final drive (2.56 vs 3.65) is huge.
In fact, to my information, the maximum wheeltorque (stock, factory data) put down is greater for the z4m (5748Nm) than for the 35is (5507Nm) (not taken drivetrain losses into account). And of course the z4m is quite a bit lighter too.

Btw the difference in max. enginetorque between the 35is and z4m is according to BMW 85Nm (63 lb.ft)
And the 40i has an LSD

[Andres]

Sorry to be off topic, but has enyone tried Mstyle garage in Romford, they're selling Quaife for 990£ or 1230£ with fitting, vat included.
I contacted them, but they're not in a hurry to reply, but so much cheaper then the ridiculous price at birdsauto of 1670£.

[Scooba_Steve]

Sorry to be off topic

Why not just start a new one then?

[abar121]

Only in horsepower. The turbo models usually have a lot more torque though (e.g. the 35is/40i have about 100lb/ft more than a Z4M) - which is where an LSD would help putting the power down.

It's lb.ft, not lb/ft
the engine torque itself is not really an issue. It's wheeltorque that breaks traction, not enginetorque. So gear ratio's have to be taken into account.
Just the difference in final drive (2.56 vs 3.65) is huge.
In fact, to my information, the maximum wheeltorque (stock, factory data) put down is greater for the z4m (5748Nm) than for the 35is (5507Nm) (not taken drivetrain losses into account). And of course the z4m is quite a bit lighter too.

Btw the difference in max. enginetorque between the 35is and z4m is according to BMW 85Nm (63 lb.ft)
And the 40i has an LSD

Exactly. Torque is amplified by the gearbox, to give tractive force at the rear wheels. You need to make torque fast (power), to take advantage of this. Is like the 335d owner's boasting that chipped motors have more torque than a C63, but then forgetting that they have to run gearing that is ~1/3rd longer. So you can take that off the tractive force, straight away.

This is commonly mis understood. Have a read here. https://www.onpointdyno.com/understandi ... ive-force/

[Ed.Straker]

This extract from https://www.automobile-catalog.com/mode ... 4_e89.html which shows a number of published data and computer simulations encapsulates the discussion..

BHP wise the 35is and the Z4M are closely matched..according to BMW the Z4M has 335PS vs 340 PS for the 35is and 355nm vs 450nm

The graphs superimposed show how they line up..

So as was stated if you run both cars through the gears then they are closely matched with the Z4M edging out the 35is..

So what does that big torque number give lower down?

If you look at the acceleration roll ons without shifting down then the 35is fairly significantly tramps over the Z4M?

[Andres]

Sorry to be off topic

Yeah I probably will do, got a few more questions about it

[GuidoK]

There is of course also another big difference between the z4m and e89, and that is that traction control systems have gotten way better in that generationdifference, and still continue to improve.
So in real world performance differences they play a huge role.
In a modern powerful rwd car, if you can switch off traction control, you will not get close to setting a performance acceleration time (on normal street/street tyres) to the one set with traction control on.
However, if I take my car (e85 ph1, but modified), when traction control kicks in, it costs me at least 0,5 sec or more as when it interferes, it pretty much switches off the power delivery and you almost hit the windscreen with your head... So for me, the best acceleration times I get is when I feather the throttle about 50% in first.
So besides the z4m having an LSD and the 35i/35is doesnt, it also probably needs it more, as it prevents traction control kicking in (in real life situations).

Same goes for esp; the e89 esp system is much more advanced than the e85 esp system. The e85 esp/tc systems are pretty much 1st gen, developped in the mid/late 90's (e46 platform)
The g29 goes a step further; it's LSD is a proper torque vectoring unit, so actively improving cornering.

Because the e85 esp/tc system is so bad, an lsd very much improves the normal spirited driving (with all the safety's on), as it pushes the boundries where those systems start to interfere. Like the slipping of an inner wheel when driving away in a corner normally immediately sets off the traction control, taking away all the power abruptly in the e85. The LSD prevents that.

[abar121]

The US Z4M has 335ps, the Euro version 343ps.

The traction control on the M is quite primitive as mentioned. On the plus side, it's not overtly sensitive like an E39 M5, so you can drive it pretty hard and have some slip angle, provided you keep it balanced. On the road anyway and so not too intrusive and easy to work with. But then it won't save you if you are really ham-fisted.

On the track, forget it and turn it off. You can enable the M track mode, which some people find useful at least.

The 35is is DCT only, which weight penalty aside, really helps the acceleration figures. Being an auto with 7 gears, there's not relevance in comparing any in gear figures really. Who's going to do that? Just kick the bugger down!

[Mr Tidy]

So what does that big torque number give lower down?

If you look at the acceleration roll ons without shifting down then the 35is fairly significantly tramps over the Z4M?

True, but if you use the right gear the M makes the 35is look a bit sluggish!

And hopefully you don't buy an M with a manual gearbox to be in the wrong gear when you want to make some progress - I certainly didn't.

BTW the graphs show the M as 343PS and the 35is as 340PS, rather than what you quoted at the start of your post.

And back on topic the M has an LSD, the 35is doesn't!

[samuelee46328i]

booloveblankie, hi you have news ? i need a lsd188k and i want know if blackline is a good choise !!

[Vanne]

Hi all,
Might be a first time poster but saw some misinformation posted here and figured I could clarify some things - especially given the thread has already been revived...

I bought a Blackline 188K after umming and ahhing as it's a lesser known brand and has the typical "chinese made" bad rap. It's getting installed in my 130i on Monday so I can't give any usage feedback yet - but I am a mechanical engineer with experience in custom manufactured gear sets so I figured my comments and pictures might be useful.

Firstly, this is almost an exact copy of the Quaife diff posted above. It has 11 (not 5!) radial bolts + 1 dowel for locating. The only evident difference I can see comparing my photos to Guido's is that the Blackline diff has full threaded fasteners whereas the Quaife fasteners have some shank remaining.

Apparently I didn't take any exterior photos except for when I immediately took it out of the box - didn't expect to be documenting this for posterity! Don't be fooled - the photo on the box doesn't match the supplied diff.




On the whole, the machining is good but they have evidently struggled with deburring. Where the bottom of the gear pockets broke through the exterior of the housing the steel has chipped very brittlely. These did not get fettled or deburred prior to assembly. It wouldn't have any effect on the performance of the unit but it bothered me enough to pull the diff apart - if for nothing else to tidy these pockets up a little.

Before:


After:


The other half of the housing evidently had similar issues when being drilled but Blackline did deburr these holes internally. Results aren't great but they're not the end of the world.

A Quaife uses 6 sets of gears. More gearsets=stronger diff with less load per gear, so also less wear.

Yes and no. The 5 gearsets would likely be a larger module (size) so would comfortably make up for the increased load per gear by having stronger individual gears. Plus you can always move to a stronger material to increase your gear strength. There are many types of steel to choose from with wildly varying strengths.

doesn't need the oil changing after 500 miles to "get rid of produced swarf" which will "decrease with use"

That's indicative of the gears not being run in. Most gearsets will have some sort of run-in process to self-tolerance the gears. No manufacturing process is 100% perfect so there will always be minor amounts of filings coming off as the gears mesh for the first time. As the gears continue meshing, particularly under load, the surface finish gets smoother and gear geometry matches closer and closer. If you're expecting big curls of swarf, you'll be disappointed. Maybe Quaife and MFactory have a run-in process at the factory. Maybe they superfinish their gears. Doesn't bother me much regardless, it's hardly difficult to do an oil change on a diff

Hope this has cleared some things up. Definitely a case of getting what you pay for in regards to the overall finish of the diff, but I can't see any reason why these issues would affect the functionality. Assuming their steel is forged 8620 and their heat treatments are within spec this should be a great addition to my car! Frankly, being a tight bastard, I'm pretty happy to have saved the money compared to buying a Quaife diff. If I were to buy another I would consider the MFactory unit - it was my other key option but a little more expensive and wasn't instock locally anyway. I haven't seen any disassembly pictures of those so hard to say how they compare.

Will post an update some time after it's installed!

Excellent post, thank you