Differential Review: OEM->JDM->Quaife->OS GIken

[fatboyz39]

Interesting read.

[lukits01]

Yes, very smooth and silent when used with Motul FF LSD Type II oil. It's good shit. I replace my oil with my Cusco dif every 10,000km's or 2 track days.

oh cool, first hand account
do you notice any more noise before you change oil?
is there noticable particles in the old oil?

[K.C.]

now i know why some LSD are noisy..

Some LSDs have a very high initial lock and they will click and pop no matter what fluids are used. Cusco/ OS Giken do not require a high initial lock to attain the level of performance expected from a plate LSD. This is due to their clever designs.... our plate diff does not require a high initial lock either... :secret::P

so i guess is either Cusco or OS Giken or Mfactory for me. W00t

[ewendc2r]

Very interesting -- the diff (even in R's) is one of the most commonly overlooked item when looking to improve performance -- A good diff will shred more from your lap time than the best exhaust out there which begs the question, why people hardly look at the Diff as an item to upgrade? Only conclusion I can draw is that because you can't see it (or hopefully hear it) from the outside lol ..

Interesting article -- I was looking at a KAAZ unit, I know they are noisy but some reports said they had excellent pickup on turn-in. This has changed my mind a bit, seems OS isn't such a bad animal afterall :P

Now does everyone know the advantages / disadvantages of 1 vs 1.5 vs 2 way design for our FWD cars??? AFAIK the 2 ways can be quite frustrating on a FWD car, but never driven in a car with one (maybe for a good reason).. Perhaps someone with a good working knowledge / hands-on experience can explain ..

Other thing, I wonder if there are active differentials out there for FWD (i.e varying rates of slip and pickup dependant on surface / direction of car relative to steering angle etc) ..

[maracer]

Very interesting -- the diff (even in R's) is one of the most commonly overlooked item when looking to improve performance -- A good diff will shred more from your lap time than the best exhaust out there which begs the question, why people hardly look at the Diff as an item to upgrade? Only conclusion I can draw is that because you can't see it (or hopefully hear it) from the outside lol

You have a very valid point here.
Maybe you should ask yourself this......

Who can i trust, Who can do the job, Who understands the job to be done.

My experience is because there are so many mechanics out there that are FFFFFFF,
just the ask of question to do the job and so forth, it's like I'm asking them to reinvent the wheel.

Fark me, if i went to school to be a mechanic, sure they would have covered this.
Or maybe the torque settings on a sump bolt is more the job for most of them.
Just my experience......this is on my mod's to do list...lol

[lukits01]

now i know why some LSD are noisy..


so i guess is either Cusco or OS Giken or Mfactory for me. W00t

isn't M's Factory a Torsen Differential?

[ChargeR]

isn't M's Factory a Torsen Differential?

I thought that was the case too, but apparently they make both Helical/Torsen and clutch LSDs: LINKY.

[tinkerbell]

why people hardly look at the Diff as an item to upgrade? Only conclusion I can draw is that because you can't see it (or hopefully hear it) from the outside lol ..

also - a diff upgrade is not a "bolt-on" job though...

also - going from non-LSD to ITR torsen LSD was like night and day for me in my VTiR...

[quenjose]

on the same topic,

i have a question with regards to a torque sensing LSD (eg OEM).

A torque sensing LSD works on the premise of torque being applied to both driveshafts, but what happens when you're mid corner and you clutch in to change a gear(no torque applied to driveshafts)?

For that fraction of a sec, is the diff open, or is the LSD still biasing the driveshafts?

thanks

[ewendc2r]

interesting question. Assuming that it is electrically activated I would think/hope that during testing (research and development) that this would have been programmed in (i.e. the clutch being depressed condition) such that it would maintain the torque setting until clutch is re-engaged and it then continues to repeatedly re-assesses the traction scenario..

Might do some reading .. Also, I thought the way the unit you are describing works by applying braking force to a wheel such that it becomes more difficult to spin thus transferring more torque to the other wheel? Not exactly a performance gain, more of a safety thing, as I would imagine that it would be no faster at the end of the day than driving an open-diff through the corner with a great deal of control (reaching that 'sweet spot' so to speak).

Might be wrong tho .. ?

EDIT - Just realised you are talking about LSD not the VSD or whatever it is in a Euro for example.

EDIT 2 - I would imagine since it is mechanical that if it has time to recover into an open condition (i.e. springs / clutches return) then it would which is more reason to short-shift and not put yourself in that position in the first place hopefully.

[quenjose]

EDIT 2 - I would imagine since it is mechanical that if it has time to recover into an open condition (i.e. springs / clutches return) then it would which is more reason to short-shift and not put yourself in that position in the first place hopefully.

yeah, i was referring to a mechanical LSD like on a DC2/5.
...of course in an ideal situation, you would avoid shifting mid corner to avoid upsetting the balance of the car... but i'm more interested to know because theres been a few times where i've upshifted just after the apex of a corner so i can get on the throttle early for the straight. But rather than the car go wide as you would expect when its clutched in momentarily, i get a slight dose of oversteer... is this because the LSD is still biasing the front wheels? or am i just doing things wrong? lol

[ewendc2r]

ahhh.

Ok that is basically a result of change in momentum (however minimal you make it). Essentially the drive is removed from the front wheels which previously were 'towing' the rear of the car. Since there is suddenly a change in momentum (which effects suspension and weight loading for that instant) the back of the car tries to overtake the front of the car (essentially the same as lift off oversteer). In fact, I'd say the problem is moreso with the lift-off accelerator as you change gears instead of the actual motion of changing the gears and the effect it has on LSD.

I know this is bad, and it shouldn't be promoted. But flat-shifting will help this, just minimise the number of times you have to do it because it will eventually damage the gearbox / clutch combination. The Hondata units actually provide a solution to this which disengages throttle as the gear engages however allowing essentially a flat-shift.

Now knowing what can induce lift-off oversteer, you can use it to negotiate tight corners, especially where the radius tightens as you progress through the corner.. Careful, if you have modified the rear sway bar this will increase the 'flick' you will get along with a handful of other mods (including suspension setup if you have aftermarket coilovers). It can become very twitchy especially if you are trail-braking into the corner initially... almost have to react as quickly / simultaneously as you would pulling the handbrake .. When you nail it, you can almost zero-counter through the corner providing the best tractive effort (look at the traction circle for better explanation). However there is 'fast' which is minimal slip angle and there is showy, which looks like a rally / drift maneuovre.. Note that the fastest method on tarmac is with slight slip angle, to a point where it feels the car is in a neutral 'G' position from the drivers perspective kinda .. Hard to explain, but yeah, you don't want to over do it.

Hope that helps.

With some diffs (esp 2 way) that act on deceleration as well, this can further the impact of lift-off oversteer (FWD mainly as generally it is meant to keep more tractive effort from my understanding in a great range of situations, but not necessarily what you want in all situations) but thats another story for another day..

[quenjose]

i initially thought it was lift-off oversteer...
but then i thought i hadnt really lifted-off... i clutched in to upshift...
if anything, shouldnt clutching in at speed increase the forward momentum... or not?
i could be wrong here...

but i see what your saying though... which makes sense
since clutching in effectively throws the weight of the car from the back to the front wheels... until u start accelerating again, which explains the moment of oversteer

nothing to do with the LSD. (which means its open during clutch in?)

couldnt really bring myself to try flat-shifting though... i love my car too much...

thanks ewen

[ewendc2r]

Yeah it only requires an instant change of momentum to upset a cars balance considerably. And flat shifting isn't SO bad, its just it shouldn't be promoted as some people will do it daily (instead of race conditions, and i mean on a track where it actually serves a purpose rather than my dick is bigger than yours drags at the traffic lights lol). I would only really do it from 2nd to 3rd, I don't think there is massive advantage in 3rd - 4th due to acceleration slowing anyhow & 1st to 2nd is just too rough on the drivetrain imho.

So yeah I would think that the diff would start to return to an open condition, depending on the speed at which this happens (I'm assuming very quickly) to then recover to a limited slip position when power is re-applied..

Damn I'm keen to get back to a track..