Rx8 LSD
 

how does this torque sensing lsd work and is it good for drifting? if not what are some good lsds?

Cusco is working on an LSD and it should be available soon.

Google is your friend. http://www.torsen.com/general/general_faq.htm

Further reading on the different types of diffs (ie, 1 way 1.5 way, 2 way)

http://www.club4ag.com/faq%20and%20t...ential_101.htm

i think the RX-8's LSD is a Tochigi - Fuji unit
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WELLBUTRIN SETTLEMENT INFO

Yes, it comes from a different manufacturer, but it's still a TORque SENsing unit, functionally similar to the TORSEN. Torsen tries to prevent its trade name being used as the generic descriptor for this type of diff, to prevent it falling into general usage and thus being useless as a trademark, such as Aspirin and Escalator have become.

Just to throw a monkey wrench into things, there are also Automatic Torque Bias Differentials like quaife http://www.quaifeamerica.com/
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Iolite Vaporizer Safety

I think you'll find that the Quaife unit is also a Torsen-style unit. The description of its operation is the same, and the cutaway diagram shows it uses a worm gear arrangement similar to every other torque sensing unit.

Quaifes are awesome! Lifetime warranty, bulletproof. I have 2 in my Subau :)

There are two major differences. Pro: no clutch plates to wear out or service. Con: if one wheel lifts off the ground, it immediately acts like an open diff. I think the con is negligible and really like the "no servicing" part. Remember the first initial in "LSD" is lmiited--after a certian point the inside wheel will start to spin. The Quaife doesn't do that. Also based on the previous explanation of 1-way vs. 2-way LSD, I believe because the Quaife is completely gear driven it acts like a 2-way. Here's some more info on various differentials:

Limited Slip Differential
This is basically a device fitted in place of the standard diff and it allows the wheels to have a small difference in speed but will not increase this difference even if one of the wheels has lost traction and wants to spin faster. In plain English this means that your vehicle will be able to negotiate corners on tarmac as normal, but if you were to lose traction off road, instead of one wheel spinning uselessly and the other staying still, both wheels would turn at a similar speed propelling the vehicle forward. LSDs (Limited Slip Diffs) are available for many vehicles from quad bikes through to Toyota and other Japanese four wheel drives.

Viscous Control Units
VCUs are very similar in operation to the LSD above. Originally developed by the great engineer Harry Ferguson, of Massey Ferguson tractor fame, they have found their most common home replacing the centre diff lock in Range Rovers since 1989.

The VCU works by letting a certain amount of movement occur between the wheels (for cornering etc.) but if this is exceeded the device locks up solid like a diff lock. Essentially this system works well but many people have found, particularly at low speeds, the device gets confused and doesn't always lock up properly. However on the plus side it requires zero operator input.

Quaife Diffs
It is very difficult to explain how the Quaife diff works, quite simply because even the inventor Ron Quaife, claims to not understand it exactly just that "?it works and that's all that really matters". The best description for them is a torque biasing differential. This means that it distributes the torque, or twisting motion, to the wheel that needs it but no more than it needs. Their effect is most noticeable at speed which has resulted in their fitment into many of the cars on the Dakar rally as well as in many conventional rally cars. I personally have had them fitted front and back in my own Defender 90 for over two years and now swear by them. My own opinion is similar to that of Mr. Quaife's; they work. Occasionally it has been necessary at slow speeds to dab the brake pedal to set up the torque reaction and get them to work particularly when horribly cross-axled. In one instance we were in a situation with two opposing wheels high on rocks and the other two floating in mid air an not moving forward. In a normal car this would have resulted in a need for a tow, but by simply engaging a low gear and dabbing the brake pedal the car moved ever so gently forward and back on to the level. What more do you want?

Lockright
The Lockright was originally conceived for the US military and utilises space age materials but has recently found its niche market in Australia. The unit works on a completely different concept to all the other devices. The unit that replaces the centre of a conventional diff is permanently locked. However when it comes to negotiating corners the outside wheel is allowed to rotate faster. This means it will corner effectively on tarmac, but in off road conditions no wheel is allowed to rotate slower than it's driven speed. The only disadvantage with the system is that at present it does not like permanent four wheel drive systems (e.g. current Land Rover products) for road usage.
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Mary jane

The RX-8 Tochigi-Fuji torsen-type unit is pre-loaded, so it doesn't suffer from the zero traction problem that no-load Torsen units do (like those used in the 94-02 Miata, for example). The Quaife could also be another example of a pre-loaded torsen type.

Regards,
Gordon

so which of them would be good for drifting?

a solid (fully locked) rear axle is probably best for drifting, to keep both wheels spinning equally.

Can someone help me out here, is a Torsen diff a helical diff?

If so then the Diff in the RX-8 is not a torsen.

From the pics I've seen it looks more like a phantom grip stlye of diff. HD Spring pressing the gears against the housing to create the lockup effect.

It could very well be that the cutaways I have seen do not show the inner gears though.

CUSCO's RX-7 LSD is compatible with the RX-8 FYI. If companies do come out with an LSD, 1.5 way will most likely be the choice.

Not sure what you mean - all diffs use helical-cut gears. The RX-8 diff is definitely a Torsen style, with helical-cut worm gears.

Regards,
Gordon

My understanding of a helical diff is a diff with a worm gear center.

The pics of the RX-8's diff show it to have a spring in it's center. with crown gears along the perimiter of the housing

The RX-8's diff certainly is a torque-sensing unit, but it has a lower TBR (torque bias ratio) than that fitted to the late RX-7's.

The FD's TBR was 2.8, while the RX-8's is only 2.0. This means that the 8's diff will send up to 2/3 of the available torque to the wheel with the greater traction, while the FD's could transmit nearly 3/4 to that wheel. While a higher TBR is useful in spirited and competition driving, a higher TBR makes the diff's action more intrusive. I guess the lower TBR was yet another compromise towards everyday civility in the RX-8's design spec.

If LSD is such a great thing, why does Mazda even offer the automatic without it? Don't they feel bad about that? Frankly, I wish it were offerred as a separate option, rather than as part of the "sport package".

I think it's because people who are interested in performance aren't going to buy an auto. Now if you'll excuse me, I am going to go put on my nomex.

Re: Rx8 LSD
 

The OE Torsen LSD in our RX8's is plenty fine for drifting. I wouldn't go with a more expensive clutch type(Cusco or KAAZ) until you are making big power and have a crazy suspension...


Aftermarket LSD's are recommended in the AE86 world, because most of the OE LSD's were marginal and 15-20 years of wear and tear just wear them out. Brand new OE LSD's are hard to find and expensive, it just makes sense to get a stronger aftermarket LSD. I never had any aftermarket units in my AE86's...I was lucky enough to find really tight low mileage units that worked flawlessly.

And those Viscous type LSD's...they suck.

Re: Re: Rx8 LSD
 

...they work well in the right application (such as a centre differential in an AWD system).

You are correct...they work good in the center....

What darkducati said - a Torsen diff only makes a difference in at-the-limit handling, ie at the limits of the performance envelope. The performance envelope is much smaller in the Auto RX-8 (well, at least in the acceleration direction), so Mazda figures that buyers of the Auto are less interested in maximizing performance.

FWIW, for the entire time that a Torsen LSD has been available on the Miata (since 1994), the auto cars have never had it available. Ie, if the Torsen was standard on the Leather Package - it was only the manual trans LPs, not the auto trans LP.

Regards,
Gordon

One more bit of information I'll toss in here - Torsen type units are quite bullet proof, with one exception as I understand it. They really do not like wheel hop during drag racing. They can take lots of torque if you keep the wheels on the ground, but when the wheels start hopping the impact loads can be very damaging to a Torsen.

I've picked this bit of information up by following the forced induction Miata crowd. If it's not true then somebody please chime in with other information. But, as I understand it, you should be carefull if you are into drag racing your '8. Too much wheel hop could result in a catastrophic failure of the diff. Yes, the transmission does seem to be the weak link for now, but I'd be carefull with the diff just the same.

George

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.

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.

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!

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

This LSD comes with the Grand Touring package

it all comes in all forms of the 6spd manual

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)

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 )

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.

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.

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

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.

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

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. :)

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......

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?

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.

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

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!

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.

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.....

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?

Did you read this thread before posting?

Yes, but it did not answer my specific questions.

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