The best performing non-DCCD centre diff??
 

Ok, got into a bit of a debate with some friends on the weekend re: centre diffs. Of course there is Subaru's flagship DCCD which I have flogged in every shape and form of STi round the track while instructing (perks of the job!) and have now wired up in my 6 speed, tested round the track and fairly impressed!!

However to my knowledge Subaru have also released 3 other non-DCCD centre diffs with factory set pre-loads. These are 4Kg, 12Kg and 20Kg? Respectively...

The 4Kg centre diff being most common in most WRX in my experience is fairly doughy inducing heaps of understeer (which most attempt to somewhat 'cure' with suspension mods etc), the 12Kg seems to be superb offering a well balanced, more nuetral drive, but have never tried the 20Kg- which I hear can get a little tricky and end up throwing the car back into understeer issues again.

So thought I'd throw out this question to the guys who have tinkered with any/ all 3 of these variations or had them inclusive within vehicles (eg- early STi's) to get their opinions... what are the differences? And which did you feel was the best??

there is also an 8kg

There are also the Cusco Tarmac Center diffs which is very similar to running a DCCD box with no power going into it.

And Cusco and ATS also make 2 way plated mechanical center diffs. Similar in operation to a 2 way rear LSD. It locks up hard under power and throttle off. And opens up when coasting.

I haven't driven on either of these though.

Just to clarify Joel, To my knowledge the 12 and 20Kg/m were not STi and STi/Ra default fitment. To assume that any STi or Ra automatically has one would be incorrect.
I've never found anything other than a boring old 4kg/m softie in any road going non dccd STi. If the car was rallied or 'dirt trial' raced in Japan you may be lucky enough to find one fitted.

I've tried all of them.
Stock 4 kg needs help to stop excessive front wheel spin.
12 is my pick as better than the rest. Does the job nicely, no nasty side efects.
20 behaves like a 12 but has noticable bind on tight turns.

My old series 1 Legacy had approx 220 horsepower at the most. A 20kg/m may have been more beneficial if the car was more powerful. I now have a DCCD centre in there and I'm seriously considering going back to a 12. The DCCD is less predictable.
I did loads of *handbrake turns with the 12 and the 20, so don't let anyone tell you it can't be done. *must have a hydraulic handbrake, plate rear diff also desireable.

cusco tarmac gear is the diff of choice for a tarmac based car, 65/35 rear front power split, has turned our car into an oversteering demon, but with a working front diff, entirely driveable, will not fall apart like a electronic dccd centre at around the 300hp mark and is about the $1200 mark making it excellent bang for buck

I was very happy with my 12kg center and it did reduce understeer whilst allowsing predictable tail out action. I have never heard the stories of not being able to use the handbrake with the 12kg but I can also confirm handbrake turns can be achieved with a 12kg center.

i like burnouts in general, so any diff that encourages it, can only be a good thing.

[QUOTE=Denver;445024]will not fall apart like a electronic dccd centre at around the 300hp mark[/QUOTE]

Is that true? A regular occurrence like gearboxes?

protofail kept toasting his, he did some digging and found a lot of people making over 300 ATW had simular issues, switch to tarmac gear, problems go away..

being electrically controlled, increasing the power input by a very large amount will in time kill it, especially if your motorsporting a lot, mechanical solutions are generally the only reliable way to do these things as power increases will not affect them as much...

I am of agreeance, in any form of motorsport or ahrd use the DCCD centre is really only good on a stockish powered car