HLSD secret...

[timtiminy]

I cannot find for the life of me the torque biasing ratio (TBR) for the stock S15 helical (torsen) hlsd differential. The reason for asking is because i would like to see if it has a higher or lower torque biasing ratio than a quaife atb hlsd. I have yet to find out the TBR of either, so if by some way you know the TBR of the S15 unit and Quaife unit and could tell me, that would be great. I have seen the OBX lsd for the 240sx and supposedly they are a direct copy of the Quaife Atb that is no longer made so i would figure they would have the same TBR... If anyone knows the TBR of the OBX unit as well that would be great. This information seems to be unknown everywhere i search...Its a secret i guess...anyone out there know??? I think that this would be the best way to decide which hlsd is right for your application. As a side note i am NOT looking for ring and pinion gear ratios (final drive ratios)

[DoriftoSlut]

I have an HLSD secret too:







THROW IT IN THE GARBAGE.









Get a Clutch diff!

[wootwoot]

They should be the same because of the design. It does not require a torque input for both wheels to spin together because they dont. It almost switches back and forth between which wheel has torque and which doesnt. Whichever wheel has the most grip gets all the power until it slips then the other wheel gets power then it slips then the other wheel gets power then it slips then the other wheel gets power then it slips then the other...

Why not call Quaife?.... OBX is going to be of less quality big time.
and I liked my helical considerably.

[naed240sx]

They should be the same because of the design. It does not require a torque input for both wheels to spin together because they dont. It almost switches back and forth between which wheel has torque and which doesnt. Whichever wheel has the most grip gets all the power until it slips then the other wheel gets power then it slips then the other wheel gets power then it slips then the other wheel gets power then it slips then the other...


This IS the worst description of how a helical differential works that I have ever heard. No offence, but it's the truth. First of all, helical differentials can be designed with many different torque biasing ratios, secondly, your description of power delivery is way off.

There are two main types of helical differentials. The type 1 and type 2. The type 1 uses high-helix angle gears combined with spur gears to substitute the side and spider gears in a conventional differential. The outer gears of this type of helical diff reside on axis perpendicular to the axis that the axles rotate on. It looks like this:

http://www.torsen.com/images/T1_wpl.jpg

The type 2 places all of the gears on parallel shafts.

http://rovermgphotos4.free.fr/doc/torsenB.jpg

Type 1's typically have much higher tbrs, ranging from around 7:1 to 2.5:1.
Type 2's typically have much lower tbrs ranging from 1.8:1 to 3:1.


TBR depends on the gear angles, design type, materials used and oil used.

Helical diffs do not "switch back and forth" between the wheels when delivering power. They are continuously variable in the way that they deliver torque, and can deliver an infinate number of torque splits. They actively adjust torque delivery.
Helical diffs do not deliver ALL of the torque to the wheel with the most grip, they split the torque delivered to each wheel proportionally according to the difference in frictional force at each wheel. If this difference exceeds the torque biasing ratio, all of the torque will then be transferred to the wheel with the least grip (If you lift a wheel, the ratio of friction will be 1:0, so all of the torque will go to the lifted wheel). What is cool about helical differentials is that they do not need to have a wheel slip to begin working. They are continuously providing varying amounts of torque to each wheel.


To the original poster: I have wondered the same thing myself for a long time. The s15 differential happens to be a type 2, but I cannot find an exact TBR for it. I was worried about the possibility of experiencing inside wheel spinup with an s15 diff because of a potentially low tbr. I installed one over the summer, and can now see that I was worrying for nothing. The only time I have ever exceeded the capability of the diff to split torque according to available grip at each wheel is when lifting wheels going up driveways. At any other time, whether it be drifting or driving grip on some backroads, I get perfect torque delivery. More torque to the outside, less to the inside wheel, and if pushed, both wheels break loose at the exact same moment.

Although finding TBR data for the s15 diff is impossible, don't worry about it. It is high enough to prevent spinup from ocurring unless you have a poorly setup suspension that lifts the inside rear wheel when cornering.

[timtiminy]

Thanks for your post naed240sx. I wasn't aware that the S15 hlsd was a completely different design, i was under the impression that the quaife style hlsd was the same as the S15 one. Seems that the quaife TBR should be higher than the S15, I hear most of the Quaife ATB hlsds are 3:1 ; I am figuring that the S15 one is probably 2:1 as most oem hlsds are about that or lower; not being agressive for the "average" consumer . I wonder if there is a way to figure out the TBR? perhaps some type of spit wheel dyno where load can be adjusted per wheel and torque split measured. oh and i believe you meant More torque to the outside wheel, less to the inside wheel... in the last sentance of your second to last paragraph. I got what you meant though. As for people saying that HLSD or useless for drift, i wouldnt think they are since once both wheels break loose it should go to a 50/50 split, just harder to initialize the drift i would imagine.

As for DoriftoSlut, I appreciate your comment, but I am looking to set up my car for grip not drift and a HLSD is more to my liking and more conducive for this. We are all free to voice our oppinions just try not to be such a jerk about it next time. Thanks

[naed240sx]

Thanks for your post naed240sx. I wasn't aware that the S15 hlsd was a completely different design, i was under the impression that the quaife style hlsd was the same as the S15 one. Seems that the quaife TBR should be higher than the S15, I hear most of the Quaife ATB hlsds are 3:1 ; I am figuring that the S15 one is probably 2:1 as most oem hlsds are about that or lower; not being agressive for the "average" consumer .
From what I remember, and from what I have read, Quaife's ATB differentials are all type 2's, meaning that they are in fact the same design as the s15 diffs, although the tbr could still differ because of different gear cuts.


I wonder if there is a way to figure out the TBR? perhaps some type of spit wheel dyno where load can be adjusted per wheel and torque split measured.

Yes, something could certainly be put together to measure TBR, but certainly wouldn't be a cost effective way to decide between the two.




oh and i believe you meant More torque to the outside wheel, less to the inside wheel... in the last sentance of your second to last paragraph. I got what you meant though.

Whoops, yeah thats what I meant. Fixed.


As for people saying that HLSD or useless for drift, i wouldnt think they are since once both wheels break loose it should go to a 50/50 split, just harder to initialize the drift i would imagine.


It's certainly not worthless for drifting. I don't claim to be especially skilled myself, but I can link an entire course together, and am still running the stock ka as well as some extremely crappy tires(Well, I have RS2s for daily, but I run crappy used 205/60/15 stuff on the rear for drift). My impression is that it is FAR better than a viscous, and feels very good for drifting, but will still never be as predictable as a clutch type due to it's actively changing nature. Your statement about it delivering a 50-50 torque split after loosing traction is in fact untrue. This is because the outside wheel still has more traction than the inside wheel when sliding, because there is more load on it. Because of this, the outside wheel will get more torque when drifting, just like it would when driving grip, although the difference in torque split is less drastic because there is less load difference from inside to outside wheels when drifting versus gripping.


But remember, the only reason that anybody would desire a higher torque bias ratio would be because they happened to be experiencing spinup. I myself have never had any spinup ocurr, and neither has anybody else I know running an s15 diff. This is all the proof I need that the TBR of the s15 diff is plenty high enough.

[timtiminy]

well the 50/50 split was actually a guesstimate...makes sense though, I am sure its not too relative since both tires are spinning, not enough to really make it too hard to drift obviously. yeah i was thinking if i end up wanting to try out a drifting a bit i would just go with a welded diff since it would essentially be a 2 way with a 50/50 split and function best for drift. Oh i misunderstood..i didnt realize you stated that both were type 2. oh and wouldnt too high of a TBR cause spinup?