mdmaclean

I assume that the reason that the automatic does not have the LSD is cost. The automatic also does not have the carbon fiber driveshaft either.

darkducati

Mmmmmm....carbon fiber driveshaft



This is a huge problem in road racing too. I have heard many times about these things exploding when one wheel gets serious air (bouncing big time off of curbing). Apparently the diff acts like a standard open diff if one wheel has zero resistance and basically grenades on touchdown. So I have heard anyway, I have yet to see it for myself.

Mr M

The LSD in the RX-8 is NOT a worm-gear type torsen LSD.

Mazda calls it a "Super-LSD", its appearance is very close to a normal differential. The Super-LSD however, has friction cones (not plates, or clutches) between the side gears and the differential gear case.

If you are familiar with the operation of a normal differential, you will know that speed differences between the two wheels causes torque to be transferred through the side gears, to the pinion gears, thus allowing you to get around the corner.

This same torque forces the side gears out, towards the differential gear case, and when you get enough torque, the friction cones lock with the differential gear case and you end up with a limited-slip effect.

Obviously, if there is little speed difference between the wheels the cones won't lock and variable axle speeds allow you to get around slow corners.

The spring in the center provides preload, so the thing doesn't rattle (there is probably a more technical explanation, but for us I think this is enough).

This LSD is used in later Miatas, and is primarily designed for improved acceleration and better traction. I am not up to date with the track record of it, but its simple construction leads me to believe it is probably more sturdy than the worm-torsen design, and definitely cheaper to repair!

The Super-LSD is actually classified as a torque-sensing (tor-sen) differential though, just to confuse matters.

I'll let you make your own judgements on whether it is suitable for 'DUHrifting' or not.

Happy camping!

Mr M

Just so you know what a worm-type torsen is, here is some information on that.
Torsen differentials

JSE RX-8

This LSD comes with the Grand Touring package

sup3rbad

it all comes in all forms of the 6spd manual

MikeW

In by 'drifting' you mean swing the tail out and controlling it out there.
Then you would not want a torque sensitive differential. Since the TBR is 2:1 the inner tire is getting 2/3 and the outer is only getting 1/3.
If it was a regular differential (open) then the split would be 50/50. More torque to the outer tire would allow for higher slip angle and more oversteer. You will light up the inner tire (with enough power or lateral acceleration-weight transfer,or both) and that is what the speed sensitive torque biasing is for. (G35 coupe/sedan manual, M3, 350Z, new viper)

David_M

Actually, in a four wheel drift your in a state of extreme understeer. So the outside wheel having more torque will help modulate the drift. A two wheel drift is kinda the beginners drift, if the whole car isn't going sideways your not doing it right.

Most people start with doing donuts then move on to handbrake turns to get used to the feel controlling a car that is going sideways. They should start with track time, learning to control a car at the limits af adhesion first will tell you how fast you can go into any given corner. The best source of info on how to drift is probably the "Drift Bible". It's a video of Keiichi Tsuchiya, knowon as the "drift king" explaing basic and advanced drifting techniques.

Yes, I do follow the sport. No, I don't participate. ( Maybe when my car isn't so painfully new )

eccles

Actually, I believe you have that backwards. A Torque-sensing diff is designed to direct more torque to the wheel with the greatest need or resistance, thus in an oversteer or drift situation, more torque is directed to the outside wheel, which is exactly what you want.

At least, that's how a genuine Torsen works, and I believe that the Super LSD is functionally similar.

racerdave

I agree with Eccles on this one. That's how a torsen works, and that's how the FD I autocrossed felt.. a lot like my shifter kart when cornering under power. The power goes more to the outside wheel which rotates the car (kart) slightly while still driving forward. Awesome once you are used to it.

MikeW

No a torque sensitive differential will initially apply more torque to the inner tire (increasing the likelyhood of breaking inside traction) when it breaks traction (less weight & more torque), it will match speeds of the outer tire, and then bias more torque to the outer tire. (assuming not outside of the TBR) So in under the limit cornering, the outer rear tire has more cornering potential.

5.2 Vehicle travel through turns

In turning situations, the outside wheels of a vehicle travel over more distance than the inside wheels. Accordingly, the inside and outside drive wheels must rotate at slightly different speeds (i.e., differentiate) to maintain rolling traction with the road. A torque division between drive axles at the bias ratio is a precondition for differentiation under all circumstances of operation. Essentially, in order for one drive wheel to rotate faster than the other, the drive wheel having greater resistance to rotation slows with respect to the differential case and transfers torque to the other wheel contributing to its faster rotation. The Torsen differential resists transfers of torque between drive wheels in proportion to the torque applied to the differential housing, and this results in a larger proportion of the applied torque being delivered to the slower rotating drive wheel. Therefore, bias ratio should be selected to provide the maximum traction advantage that will still allow both drive wheels to deliver significant portions of engine torque in turns.

However, even in turning situations, the Torsen differential enhances traction management. Since
torque is already distributed in increased proportion to the inside drive wheel, it is exceedingly
unlikely that the outside drive wheel will ever exceed available traction and 'spin up'. Alternatively, should the torque of the inside wheel exceed available traction in a turn, it is equally unlikely for this wheel to 'spin up' since such a 'spin up' would still require a difference in traction between drive wheels which exceeds the bias ratio. Ordinarily, when the inside wheel exceeds available traction, differentiation ceases and torque is divided in more even proportion between drive axles determined by the maximum torque that can be sustained by the inside drive wheel. Thus, in all directions of travel, the Torsen differential will resist 'spin up' of either drive wheel by instantly dividing torque between drive axles in proportions up to the bias ratio to match prevailing traction conditions.


http://www.sonic.net/garyg/zonc/Tech...ferential.html

eccles

I stand corrected, under normal cornering. However...

In a powerslide or drift situation, where both rear wheels have exceeded their slip angles and are spinning, there is little to no speed differential between them. In this situation, the outside wheel has greater resistance due to weight transfer to the outside of the turn, and will receive proportionally more torque, though the difference is likely to be minimal.

MikeW

eccles, would you call a torsen 1 differential a 2.5 way 'LSD'
sorry about the long quote

4.3 Bias ratios between drive and coast modes

It is also an important design freedom to provide for different effective bias ratios between vehicle driving and coasting modes. Since the Torsen differential is designed to have little or no effect on vehicle performance unless torque is being transferred by the differential, it should be understood that what is meant by the coasting mode is actually vehicle deceleration caused by engine braking. This mode is most evident with standard shift vehicles engaged in downshifting.

Invex gearing also makes possible this important design alternative (see Figure 7). The side gears
within the differential are designed with the same hand of helix angle. When engine power is applied to the differential (i.e., drive mode), both side gears are thrust against the same end of the differential housing. Alternatively, when the engine is used to brake the drive wheels (i.e., coast mode), the side gears are thrust against the opposite end of the housing. This feature provides an opportunity to vary frictional characteristics between opposite ends of the housing to vary bias ratios between the opposite directions of power transfer through the differential.

_The possibilities for independently varying bias
ratios between the two directions of power
transfer enables the differential to be designed
with one bias ratio to compensate for
undesirable steering effects associated with
downshifting and a second bias ratio which is
selected for most other purposes.

Ferrari 360 modena is something like 25% locking on drive and 45% on overrun. Porsche's GT2 is 40 and 60 and same for GT3

racerdave

Cool stuff. Well, my interpretation was off, but my "seat-of-the-pants" feel tells me I like the torsen's handling characteristics much better than the clutch-pack diffs on, say, C4 Vettes, etc.

NAVILESRX8

iTrader: (1)

Have any of you guys ever even drifted? A nice smooth responding and strong LSD is ideal for drifting...open diff? WTF? That is retarded for drifting....one wheel will smoke up and power being quickly transmitted 100% side to side will the make car a unstable and unresponsive......

Mr M

I was waiting for someone to say that...
Why do you all think rally cars have limited slip differentials in them?
My feeling is that a clutch-type lsd would provide a more progressive transfer, and therefore be more suited to 'drifting'.
Why doesn't someone send an e-mail to that drift-king guy in Japan and ask him?

racerdave

It depends what you want. I don't think the clutch-type is more progressive.

I don't want an LSD that kicks you sideways. If you're a drifter, you may want that.

I'm interested in going fast, not putting on a show.

For that reason, I'll take the torsen, thank you very much.

sup3rbad

Cuz he'd have a hard time answering us in english.

eccles

Indeed, that has been my experience too. The Mazda competition clutch-type differentials in my RX-3 and RX-7 race and road cars tended to make them understeer under power, as the rear wheels wanted to turn at the same rate.

In contrast, the effect of the torque-sensing diffs in my Miata and RX-8 is actually to help the car rotate under power, hence my (apparently mistaken) belief that more torque was being directed to the outside wheel. It certainly doesn't handle like the power's being delivered to the inside wheel!

racerdave

I tend to find the torsen helps rotation, but it's more controlled. The LSDs in other higher HP cars I've driven is that in an autocross situation, it kicks the back end sideways easier and momentum is lost. The torsen cars seem to rotate, yet still provide good forward momentum.

NAVILESRX8

iTrader: (1)

This is my 1st car with a Torsen diff....I love it. Very nice without the shuddering on real tight low speed turns. But, usually for drifting a strong clutch-type diff is preffered.....

pelensky

I have no been able to get a clear understanding of the type of diff my RX8 has. I have a 2004 6 speed manual. I think it might be a GT but I'm not sure since the RX8 thing is new to me.

I am going to replace the diff fluid and trans fluid. Is this a all gear differential or a does it have have slipping cones or hydraulically actuated something. I am familiar with the gear type that requires no LS additive and the belville washer spring clutch systems that require and LS additive. I also have a 2005 GTO that has a ford cone clutch system that requires a special ford LS additive.

Does this diff have slipping cones that require a LS additive or is there no slipping action?

Carbon8

iTrader: (4)

Did you read this thread before posting?

pelensky

Yes, but it did not answer my specific questions.

Carbon8

iTrader: (4)

Re-read it!

All your answer are on the first page, their are countless threads on it as well as a DIY for fluid change if you would also search which will tell you that any GL-5 is required for diff, most prefer redline 75W90