Non M LSD

[lee330sport]

Roy/Alex

My Diff is on its way out, already.....:rolleyes:

So might aswell upgrade to an LSD. Do you have any suppliers or recommendations?

So far i have a price off Kaaz for £750 + Vat, but then i have to build it myself.

Cheers

Lee

[CA Automotive UK]

I will ask my friend

good choice

Kaaz looks very good option also

[Sport Coupe]

I have never heard a bad word said about a Kaaz 2way diff.

[lee330sport]

After alot of research and some help from technik, im going for an E46 M3 rearf end including diff.

[CA Automotive UK]

best of luck Lee

[Ali]

Lee,

isn't that a serious transplant?? and isn't the diff very short??

[lee330sport]

Transplant is straight forward. I need the diff, diff carrier, propshaft and drive shafts. Its all bolt in so, aside from the costs its an easy conversion.

The standard M3 diff in 3.46, which is the same as i have now anyway.

[peppernick]

Lee I made a mistake the other day at ACE :o Standard M3 ratio is 3.62 not 3.46. Kellerners confirmed that.

[lee330sport]

Lee I made a mistake the other day at ACE :o Standard M3 ratio is 3.62 not 3.46. Kellerners confirmed that.
Oooooo thats better then. Ill have to lift the rev limit to compensate.

[Sport Coupe]

Lee, I have a few of my thoughts on the subject.

First up, I'll explain a little on how the new E46 M3 differential works, so as to help you understand later my own areas of concern.

The principal (and principle) difference between a traditional limited-slip "diff" and the new Variable M Differential Lock is that where the former senses torque, the new senses wheel speed (rpm). Under dry to not-quite-dry road conditions, the traditional limited-slip has always enhanced the handling of sporty rear-wheel-drive BMWs; however, under slippery conditions, this differential type is limited (in the literal sense) in its ability to improve traction. On all current BMW models, electronic traction control addresses this issue, although not in an optimum manner for sporty, M Car-style driving.

The Variable M Differential Lock specifically addresses low- and split-traction situations, this is the difference in rotational speed that builds up between the two drive wheels whenever one of the drive wheels loses grip, either because it has become unloaded or hit a slippery surface. Where the traditional limited-slip is a torque-sensing mechanism, this is an rpm-sensing device.

The increase in wheel speed generates pressure spontaneously in a shear pump located internally within the differential. This self-controlled pump system is maintenance free and is filled with highly viscous silicon oil between the two sheer discs. Viscous fluid is so called because it develops internal force (via an increase in viscosity) whenever it is sheared. As soon as the two sheer discs turn at different rates, the silicone oil is sheered into the grooves in the sheer plates and this generates a pressure dependent on the speed differential of the two plates. Thus, a variable differential lock effect is achieved.

As soon as the two wheels are turning the same speed, the pressure of the sheer plate’s decreases and the differential unlocks. This variable pressure created by the sheer plates is then conveyed via a piston to a multiple-plate clutch, thereby channelling power to the wheel with better grip. In an extreme case, the entire drive power of the engine may be transmitted to the wheel with better grip (provided that enough grip exists). The Variable M-differential lock system continually varies the "locking" of the two drive wheels. During cornering, the speed differential is low enough for the differential to remain unlocked so lateral stability can be maintained. As soon as one wheel looses traction, the differential holds by locking, and the car continues to move.

Overall, this is a wonderful system that works really well when combined with the fine tuned DSC system of the M3 and is a great advancement in differential technology for the road user.

BUT

1) In a performance situation the Variable M-Differential may not necessarily be the best solution. I consider it to be a 1.5 way differential as it offers good locking characteristics under acceleration due to working on RPM; however this method is not as good under de-acceleration as it is working on rpm rather than torque and rpm will be getting less the slower you go. A good 2 way (kaaz and cusco) differential works using torque and is already pre-loaded so as to help the clutch plates lock initially, thus when the torque applied through acceleration/de-acceleration increases so does the locking effect. The advantage of having a differential that has good locking characteristics under de-acceleration is that it can be used to help turn in when cornering by giving an oversteer nature.

2) A 2way differential can easily be customised to your requirements by changing the clutch plates, the amount of lock up may need to be changed around due to the power available and the amount of lock up you would like. The Variable M differential is only set to the manufacturer’s tolerances and is purely designed for the M3's power delivery. The shear pump for example only handles up to 38 Bar of pressure to lock the clutch plates.

3) Viscous silicone oil has lower heat resilience when working under extreme loads i.e. track racing/drifting/high power applications, and when this happens the differential would not work how it was designed to.
The main reason is that the locking pressure would be reduced due to the fluid not being able to shear as well.

4) Extra fiddly components that can go wrong, this is another area that is unfounded but a distinct possibility, For example the M5 on Top Gear uses a very similar diff and that had problems due to the spirited driving it received.

Just my 2p worth :D


Oh and for anyone that thinks what the hell does all that lot mean [hmm then you might want to have a look at the link below, as it explains the basics of a differential and differences between type of differential.


http://auto.howstuffworks.com/differential.htm

[lee330sport]

Wow, cheers for that mate. Thats the kind of information ive been trying to get out of people. My main concern with thw kaaz diff is, what kind of power would it take as it is only housed in the origional diff housing. I know for a fact that the standard diff cant take the power of an sc330 under heavy driving. So does the kaaz diff improve durability?

[CA Automotive UK]

excellent explanation Sport coupe , well done . I had no idea the M diff was so sophisticated ......

Lee , seems like you have your work cut out choosing a diff .

From what i have heard and read , I am thinking the Kaaz may be more suitable for you , if a bit of grief at first setting up and installing .

BTW Lee , friend of mine has an E39 M5 engine and box for sale , no vanos unit in the engine , but he only wants £2500 the lot if interested ....

[lee330sport]

Give me a price for the lot installed then Roy. With a new vanos unit, suppose thats the most expensive part. Pm me if you like. Just a ball park figure.

[Sport Coupe]

Thanks guys,

The Kaaz diffs are very good units and I have seen them used in drifting applications with over 500 BHP going through them and no probs. I do believe that the 330 casing would need to be machined a little to fit the larger clutch plates though. As im sure you aware there is not much available for the E46 series, so anything you do would be a little like the blind leading the blind :) .

Might be worth speaking to Kaaz themselves, their website is here with some contact details too.

http://www.kaazuk.com/index.php


Sam