All about LSD

[MFactory]

Originally Posted by tuj

Only if it is a hydraulic or other torque-vectoring diff. If it engages the brakes...BAD!

The ones used on high-end supercars with the GKN-developed e-Diff is a proper e-Diff i.e It has a real plate type LSD that is electronically controlled based on feedback and in conjunction with independent LSD calipers on the rear brakes

The ones used by mainstream car manufacturers are simply the ECU controlling the rear brake calipers and throttle/ignition. On their own, they work fine for general street use, but on the track, not so well. However, in conjunction with a mechanical LSD, they do work hand-in-hand.

Car manufacturers just decided to change the name from Traction Control to e-Diff, as the feature "Traction Control" is so common now, they wanted to pickup on the new buzzword for performance, which is a Limited Slip Differential (Top Gear anyone?). Basically, it's all marketing.

Unfortunately, as not everyone can afford a $200k Ferrari, the mainstream consumers have not heard of an e-Diff before, until BMW/Ford/VAG started marketing (i.e mis-using) the term.

[tuj]

MFactory Hi: I am aware of how to setup the ramps in a plate/clutch LSD so I know it can be a 1/1.5/2 depending on setup.

I'm curious about the statements regarding TC. Generally I have found (on non-BMW cars) that the TC is too intrusive, especially with racing tires. It works well with the OEM RFT tires (in fact, I set my best times with it on) but I suspect it is not setup to understand the slip angles and grip of a proper race tire. Probably if we knew how to code the module better maybe we could back the TC off and get it more like a RaceLogic system, but that seems a far day away.

So that being said, I expect to be driving on my race tires with TC off. Now I have always felt that Torsens have felt very natural to my driving style in Stock-class autocross (where you cannot modify spring rates or the rear sway) but I would still often get wheel spin on corner exit, I'm guessing due to excessive roll.

I have to admit, I do not fully understand the WaveTrac system, other than it looks like a variation of the Torsen but with some in-built locking or preload? Is this correct?

What I'm looking for in a diff is fairly progressive locking as I squeeze the throttle, I don't hammer it. My style is that I modulate the throttle to control understeer mid-corner, and then gradually increase application as I track out of the corner and unwind the wheel. I am not a left-foot braker.

Is the clutch-type 'snappy' when it locks? I suppose this is all about ramp profiles?

[MFactory]

You are correct, yes. The basic traction control is just that; basic. It is good for general street use, and is more of a "safety" feature than it is "performance". As I said though, "performance" is good for sales, so it is marketed as such.

A Helical LSD will not stop wheel-spin completely, as it can only transfer so much torque to the opposing wheel (this is what I mean with the bias ratios). Each Helical LSD has different bias ratios, but most consumers do not realise this, thus the benefits are not well known. FYI, we are the only company to allow upto 75% torque transfer; most other Helical's/Torsens are around 66%. The increased torque bias helps tremendously and is night & day difference.

For the Wavetrac, yes, they have their patented "wavelock" mechanism (which replaces the pre-load washers in a conventional Helical LSD) which, upon detecting an unloaded state, will lock the free-spinning side of the LSD and continue to bias torque as required. Traction Control serves the exact same function, but only IF you don't turn it off

I cannot go too much into the details, but suffice to say, which would you rather prefer: Increased traction during 90%+ of cornering, or increased traction during 5%+ of cornering? Of course, this scenario only applies if you are using one of the Helical/Torsen LSD's

When it comes to Plate type LSD's, then there are FAR more choices available on the market. Hint: Don't just follow blindly the "engineering talk" that "builders/mechanics/tuners" tend to spew out, as a lot of the stuff they say and advertise on their website is a complete joke, showing they have a very limited understanding of how an LSD actually works. Again, what they sell/offer/propose may do as they advertise, but so does a Honda Civic. But guess what, you chose a BMW. Why?

If you want to do thorough research, try talking to the engineers at the actual LSD manufacturers and they will tell you what's what. Don't talk to the sales people as they will have their customers best interests in mind (i.e they don't want to lose sales as these builders/mechanics/tuners also purchase their products, so they can't say their customers lack the knowledge). The difference with us is, we are both the Manufacturer & Seller, so I will always tell it as it is, regardless of these "builders/mechanics/tuners".

For your requirements, I would:

1) Forget about the OEM-Based LSD's. These are all washer/cone style LSD's (i.e old tech) and, although they may provide the beginner with the progressiveness/smoothness that they require, this is only because the LSD is inherently "weak" to begin with. There is a reason why the more experienced driver would prefer a "real" LSD, and not a cheap OEM-Based LSD. Disclaimer: Don't get me wrong, they work and serve their function, but if you want something more advanced and tunable as you progress in driver skill, this is not your best option
2) Forget about the washer/cone style multi-plate LSD's (again, old tech). For the most part, these are like on/off switches and will not provide you with the progressiveness/smoothness that you require
3) Look for an LSD that utilises pre-load springs (there are a few on the market). By switching out the pre-load mechanism from washer/cone to springs, this allows a much more progressive locking of the plates, and is generally smoother in operation.
4) Ramp profiles will determine how "aggressive" the LSD is, and does contribute to the overall "smoothness", but not as much as the pre-load mechanism
5) You need to differentiate between "noise" and "chatter/vibration". Less pre-load will make for a smoother feel (due to the plates slipping easier), but more noise. More pre-load will make for a rougher feel (due to plates slipping less), but less noise. However, there will be more "chatter/vibration", which most users generally translate to as noise

Again, I just tell it how it is. Everyone has their own thoughts on how an LSD works, and how it "should" work, but be wary of those who promote their ideals as gospel. No one person is alike, especially when it comes to driving style and preferences, so at the end of the day, what works for someone else may not work for you.

Final Note: Just to show that I'm replying to you with "advice", rather than a "sales pitch", the best Plate type LSD currently available (in terms of technology and function) is the OS giken. However, make sure you do your research as they do have an inherent flaw in their design that they have not yet (AFAIK, I may be wrong) fixed, and is why most Porsche (and a lot of BMW) owners won't use their products. As mentioned, there are other Multi-Plate, spring-loaded LSD's on the market, but in their current iteration, are not as "technically advanced" as the OS Giken.

[RyanDavies]

It wasn't on my car.

Eventually, he bailed, bought a clone diff from Diffsonline of mine and all of the issues were solved.

Gikens have their own slew of issues, but not from a performance perspective if set up properly .

A well set-up clutch diff should not be "snappy". I've driven Giken cars that felt this way, and others that don't. Their new dual-core stuff is pretty cool, haven't gotten the chance to drive a car with it.

I don't think relaying experience is "bashing". If a product has failed to meet the end user's needs, sharing that experience is going to be better for the community overall.

[MFactory]

Calling something "a fucking mess" can be seen as bashing

Sharing experience, however, is very much welcome, as it allows us to improve upon our products and also assist our customers in setting them up properly.

[Suprgnat]

Originally Posted by MFactory

1) Forget about the OEM-Based LSD's. These are all washer/cone style LSD's

I'm curious as to which "OEM-Based" LSD you are referring.

[MFactory]

The majority of these 2/3/4 clutch LSD's currently making the rounds are basically OEM-Based LSD's (i.e a modified OEM/OEM-Based Housing with custom plates)

As mentioned, nothing wrong with them and they serve their purpose, but if you want something more advanced/tunable, you need to look at a proper multi-plate LSD.

The way I see it is like this (and some may or may not agree. This is just my opinion):

1) You are a street car or occasional track car and don't want the associated hassles with noise/maintenance and, most importantly, trial-and-error setup - Go for a Helical LSD
2) You are a street car, and more advanced track car, and don't mind the associated hassles with noise/maintenance and trial-and-error setup - Go for a Plate type LSD, and get it setup correctly. The whole point of getting a Plate LSD is because it is adjustable for your driving style, not someone elses

I do not see the need for a "middle-ground", or "beginners Plate LSD", as if you are going to go for a Plate LSD, you are at the point where you are advancing your driving skill, and a cheap OEM-Based LSD will not allow you to do that without wanting to upgrade to something more advanced as your skill progresses. Unless you have the money to waste, you may as well start with a proper Plate LSD, and if you choose a good one, they can be fine-tuned to your requirements regardless whether you are a beginner, intermediate or advanced.

[Suprgnat]

Originally Posted by MFactory

The majority of these 2/3/4 clutch LSD's currently making the rounds are basically OEM-Based LSD's (i.e a modified OEM/OEM-Based Housing with custom plates)

As mentioned, nothing wrong with them and they serve their purpose, but if you want something more advanced/tunable, you need to look at a proper multi-plate LSD.

What are the "washer/cone" style to which you are referring?

[RyanDavies]

Man, those beginners at Bimmerworld! What hacks!

[MFactory]

Originally Posted by Suprgnat

What are the "washer/cone" style to which you are referring?

In order to set pre-load, these LSD's use belleville washers on the top/bottom to push against the plates, providing the pre-load.

With spring-loaded LSD's, these use coil springs to push against the plates to provide the pre-load

[MFactory]

Originally Posted by RyanDavies

Man, those beginners at Bimmerworld! What hacks!

Dan at DiffsOnline build most of their Diff Builds, and guess who supplies Dan with custom-branded LSD's?

The reality is, budget will always come first before anything else, otherwise we would all be buying the more advanced LSD's (and DiffsOnline do have more advanced, multi-plate spring-loaded LSD's available. They are just really expensive though)

[Suprgnat]

Originally Posted by MFactory

In order to set pre-load, these LSD's use belleville washers on the top/bottom to push against the plates, providing the pre-load.

With spring-loaded LSD's, these use coil springs to push against the plates to provide the pre-load

Oh, OK. I'm very familiar with Belleville spring washers.

[Suprgnat]

Originally Posted by MFactory

Forget about the OEM-Based LSD's. These are all washer/cone style LSD's (i.e old tech)

2) Forget about the washer/cone style multi-plate LSD's (again, old tech).

FWIW, BMW, Kaaz, Cusco MZ, OS Giken and Drexler all use "old tech" Belleville spring washers (and I'm sure many others). IMHO it's a disservice to recommend people "forget" about them.

[MFactory]

Originally Posted by Suprgnat

FWIW, BMW, Kaaz, Cusco MZ, OS Giken and Drexler all use "old tech" Belleville spring washers (and I'm sure many others). IMHO it's a disservice to recommend people "forget" about them.

As mentioned in my post, this was my recommendation as per the OP's requirements, NOT to everyone on this forum.

Cusco RS and OS Giken both use coil springs, and I highly recommend both of them (dependant on application/circumstance)

OEM BMW is weak, Kaaz and Cusco MZ are very on/off, so don't meet the user's requirements, and the Drexler is a zero pre-load diff which just happens to be the most expensive of all, so again, probably doesn't meet the OP's requirements.

[Suprgnat]

Originally Posted by MFactory

As mentioned in my post, this was my recommendation as per the OP's requirements, NOT to everyone on this forum.

Cusco RS and OS Giken both use coil springs, and I highly recommend both of them (dependant on application/circumstance)

OEM BMW is weak, Kaaz and Cusco MZ are very on/off, so don't meet the user's requirements, and the Drexler is a zero pre-load diff which just happens to be the most expensive of all, so again, probably doesn't meet the OP's requirements.

Again, splitting hairs, but the OS Giken does use Belleville springs for setting the initial torque and the Drexler LSD, not Drexler Adjustable LSD.

It would be fun if someone of means could get a bunch of identical cars together that only varied in their differentials so that we could try out the different types and settings side by side. (obviously not EVERY permutation is possible)

[MFactory]

The OS Giken uses coil-springs (it's what they have a patent on):



Instead of calling it pre-load though, they call it "lock-timing" or, depending who you speak to in their engineering department, "negative pre-load"

[Suprgnat]

Originally Posted by MFactory

The OS Giken uses coil-springs (it's what they have a patent on):

Instead of calling it pre-load though, they call it "lock-timing" or, depending who you speak to in their engineering department, "negative pre-load"

From the Giken web site:

"Tunability

- Initial torque can be adjusted by using thicker / thinner cone springs"

[MFactory]

Ok, this will be my last post on this particular subject, so whether you agree with me or not, it's up to you. I don't know exactly how you are missing the 12 coil-springs in the smack bang centre of that image, that just happens to be painted in yellow to highlight this significant feature.

ALL LSD's that use coil springs (such as the OS Giken, Cusco RS, MFactory Metal Plate etc) also have washers/shims on each end of the housing to fill the gap between the Plates and the LSD Housing, as you do not want the Plates to be rubbing against the housing itself. Generally, these tend to be flat washers/shims, and by changing the thickness, you can also change the pre-load. You can also change these out for Belleville washers if you so desire as Belleville washers are dynamic (relatively speaking) compared to stacked flat washers.

However, this is not the main mechanism to adjust the pre-load in these LSD's. The main mechanism is via adjustment of the coil-springs, regardless of how the manufacturer wants to word it.

If you still disagree that the OS Giken uses coil-springs, then we shall just have to agree to disagree

[Suprgnat]

Originally Posted by MFactory

Ok, this will be my last post on this particular subject, so whether you agree with me or not, it's up to you. I don't know exactly how you are missing the 12 coil-springs in the smack bang centre of that image, that just happens to be painted in yellow to highlight this significant feature.

ALL LSD's that use coil springs (such as the OS Giken, Cusco RS, MFactory Metal Plate etc) also have washers/shims on each end of the housing to fill the gap between the Plates and the LSD Housing, as you do not want the Plates to be rubbing against the housing itself. Generally, these tend to be flat washers/shims, and by changing the thickness, you can also change the pre-load. You can also change these out for Belleville washers if you so desire as Belleville washers are dynamic (relatively speaking) compared to stacked flat washers.

However, this is not the main mechanism to adjust the pre-load in these LSD's. The main mechanism is via adjustment of the coil-springs, regardless of how the manufacturer wants to word it.

If you still disagree that the OS Giken uses coil-springs, then we shall just have to agree to disagree

I never said they didn't use coil springs. I DID say they DO use Belleville springs. OS Giken DOES say that the Belleville springs are their main mechanism for adjusting preload, regardless of how you choose to interpret it. What OS Giken does say about the coil springs: "- Lock progression timing can be adjusted by using stiffer / weaker pressure ring springs, allowing the progression of full lock to be fine-tuned to the vehicle/driver." That doesn't sound like they're using the coil springs to adjust preload to me.

[MFactory]

Take a closer look at the image, and you'll see adjustable bolts inside the coil-springs to change the compression on the coil-springs, which are then used to adjust how much the cams (pressure rings) push against the plates i.e pre-load (or negative pre-load, which is what some employees at OS Giken call it as it is essentially the reverse design of all the other coil-spring setups on the market)

OS Giken do NOT say that using belleville washers is the main method of adjusting pre-load. They say it "can", exactly how you "can" with the other coil-spring LSD's on the market. And a lot of their fitments use flat washers, NOT belleville washers (the washer in the image above is flat). But again, it is easy enough to change these washers with whatever you want, as whether flat washer or belleville washer, you will still change the pre-load i.e it is NOT the type of washer, but how much pressure they put against the plates, be it stacked flat-shims, or a thick belleville washer.

Again, let's just agree to disagree.

The point I've been trying to make is, coil-spring LSD's (just forget that they also have washers/shims, as that point does not need to be mentioned), of which OS Giken is (as you have just confirmed, they do have coil-springs, regardless of whatever "they" say they are used for) is more advanced and recommended over non-coil-spring LSD's. So please, stop trying to win this pointless argument over a point that you are trying to make that doesn't exist.

[Suprgnat]

Originally Posted by MFactory

Again, let's just agree to disagree.

Sure, sounds good. Let's agree to disagree.

Originally Posted by MFactory

So please, stop trying to win this pointless argument over a point that you are trying to make that doesn't exist.

Thank you for throwing in your snide and condescending comment at the end. Way to agree to disagree.

[MFactory]

You're welcome