xvxax

What is the lockup on a 1993 r1 differential?

DamonB

That question makes no sense. The stock LSD is a Torsen type diff.

reza

maybe one way(accelleration)? it only lock both when torque is applied, hence TorSen Toque Sensitive...

xvxax

Maybe I don't understand limited slip differentials. On most I've seen a number associated, 40%, 30% etc. Maybe that is on clutch type, but how much can 1 wheel spin more than the other? I'm sorry I guess I didn't do my research. I guess I should do another search. Sorry...
Thanks anyway,
peter tyson

potatochobit

iTrader: (1)

it locks pretty quick. i added the redline 75-90 and noticed a huge improvement. even going slow in little corners it makes the wheels chirp sometimes.

911GT2

LSD differential. Is that like ABS brakes? Must be from the Deparment of Redundancy Department.

RX7SpiritR

iTrader: (1)

¿huh?

Hollis

He's asking about what percentage of differentiating wheel speed it takes before the LSD locks up and brings both wheels "in line". I.E. the inside wheel is turning 40% slower than the outside wheel, the differential locks up and tries to align both wheel speeds. So, if anyone has that number for us...

Also, quick question on my end: Is the stock differential a viscous type, or mechanical?

soru81

Hollis: Torsen is purely mehanical thingy and it doesn't include any replacable parts as clutch type lsd.

doncojones

The stock differential is a torque sensing or torque biasing type differential. The actual type of mechanism is referred to as a helical gearset or planetary gearset. It does not lock, it adjusts the torque split between the wheels.

Taken from an SCC article:

"Each axle is attached to a gear, called the sun gear, and each sun gear has several small gears around it called planet gears. The planet gears from one side mesh with the planet gears from the other side, so when you put both drive wheels in the air and turn the left wheel clockwise, the left planet gears turn counterclockwise. They turn the right planet gears clockwise, which turn the right wheel counterclockwise. In other words, the wheels spin in opposite directions just like a normal open differential.

The magic comes from all the gears having their teeth cut helically. That means the teeth are angled so that if the gear were long like a log, the gears would spiral around the log in a helix. When you put a big load on a pair of helically cut gears, there's a reaction force pushing them sideways.

The gear teeth meet at an angle, and when you try to push straight through an angled interface like that, you get shoved sideways. The latch on the front door of your house works the same way. Close the door until the latch touches the striker plate and you have a similarly angled interface. Push straight on the door, and the sideways reaction force pushes the latch into the door. In a helical differential, the reaction force shoves the sun and planet gears sideways, where they rub against the ends of their housings. This rubbing encourages both wheels to turn together.

The reaction force only happens if there's some resistance to your shove, though. If there was no resistance in our door latch example, the doorframe would just fall over. If there's no resistance from the other gear, it will just turn. This is why, technically, a helical limited slip isn't really a limited slip. Put one wheel on ice and the other on pavement, and there won't be enough resistance to prevent all the power from going to the ice. Put both tires on pavement and go around a corner, however, and if the engineers who picked the gear angles did their jobs, the gears will send more torque to the grippier outside tire in just the right proportions to keep the inside tire from spinning."

Hollis

I knew it wasn't clutch pack based, but I didn't know if it was of the viscous fluid type either, hence the question. But, Donco laid it all out for us, which is quite handy reading. Thanks for shedding some light on this don.

particleeffect

i already knew, but thanks for actually answering the question don.

David Beale

Hmmm, I'm pretty sure if I turn one wheel the other turns the same way, when both are in the air. I read the above description to say that will not happen (low friction situation). I'll test it as my car is sleeping on jackstands right now. Otherwise, it sounds like a good description.

There is no specification for % slip in the factory manual. Anyone seen one in the original sales glossies?

Torsen diffs. are patented, are they not? I note that several new vehicles sales glossies refer to their diffs. as "helical type limited slip". Are they just trying to get around the patent or missing out on the Torsen name that enthusiasts know?

Tom93R1

iTrader: (2)

howstuffworks.com has a great description of how differential work and there is a section on the torsen LSD. If I remember correctly it ends up being a torque multiplyer somewhat. If one wheel starts spinning it will multiply the torque sent to that wheel by some number and send that much torque to the other wheel. This ends up being pretty good for most any situation except in an extreme case like one wheel on wet grass and the other on dry pavement. The wheel on wet grass gets almost no torque before it starts slipping therefore almost no torque multiplied by some number is still almost no torque sent to the other wheel.

David Beale

I yield. Rotated one wheel and the other turned the opposite direction.

doncojones

Torsen is a brand name. They may have had a patent on the helical geaset diff at some point but if they did it's since expired. Quaife sells helical diffs through the aftermarket (and a few OEMs such as the '04 Dodge SRT-4) and a few other companies (Bosch, Tochigi Fuji, etc) sell them to OEMs.

AJatx

iTrader: (1)

When I rebuilt the gears on my 4WD RC truck, I saw the wheels turn in oppposite direction (sharing the same diff). I also noticed how the helical gears would catch if you had different friction surfaces on each wheel. Of course, it's not as complex as the diffs in our cars, but it gave me an idea on how it works.

I also learned that most stock diffs (unless you get a Rubicon or an old Mercedes MOG) really don't lock when you have no traction on one wheel and traction on the other. Some of the torque can be transferred, but not enough when you go for serious rock crawling or get stuck in a hairy situation. I'll need some Detroit lockers or decent air lockers for my truck.

J

xvxax

So how close to complete lockup do these differentials get at any given time?
Thanks a lot for the answers, you guys know your stuff :-)
Peter Tyson

particleeffect

~100% when even traction on both tires. and it tapers on down from there depending on how much grip the "slip" wheel has that can be multiplied to the "grip" wheel. it'll never lock up totally the way a clutch type will, but it makes for really smooth torque transitions and turn feel, unlike some on/off clutch types.

doncojones

Oh btw I can't actually take credit for writing that mini dissertation, I copy n pasted from this article: http://www.sportcompactcarweb.com/pr...cc_projslivia/

79CI13B

What other do you have besides stock LSD?

79CI13B

oooops I meant what other OPTIONS

particleeffect

t2 clutch type, kazz clutch among other aftermarket diffs. they're definatly out there as far as clutch types.

soru81

I hear nismo clutch type is also very good (efficient as kaaz, but quieter), but I could not find the distributor in us or europe... Imamura uses it in his white FD, so it might be true.

doncojones

I wouldn't really switch from the stock Torsen (helical gearset) to a clutch type unless you're going to be drag racing or making 400 hp at the wheels. A clutch type diff will provide better launching than the Torsen at the expense of a less smooth transition in torque bias than the Torsen, which tends to make the car handle less predictably at the limit. Also the Torsen diff does like to blow up every once in a while when subjected to high power levels.

So yeah I'd keep the stock diff unless you're building a drag-only or drag-biased (i.e. you don't care so much about how it handles) car, or are making a buttload of power at the wheels to the point of popping the Torsen.