i thought lsd's are there to help handling such as cornering and stuff

but i see some people saying like it acts like traction control.
for example~ "we can launch our car at higher rpm cuz we got lsd~"

so i am confused here what is LSD for?? thx

 

Limited Slip Differential

 

i know LSD stands for Limited Slip Differential but What i am asking is what is IT for?

 

limits tire spin

 

...each wheel spins independently, allowing better grip/traction...much harder or nearly impossible to spin both tires at the same time

 

http://www.howstuffworks.com/differential6.htm

 

so you mean it works like traction control??

 

The spring pack pushes the side gears against the clutches, which are attached to the cage. Both side gears spin with the cage when both wheels are moving at the same speed, and the clutches aren't really needed -- the only time the clutches step in is when something happens to make one wheel spin faster than the other, as in a turn. The clutches fight this behavior, wanting both wheels to go the same speed. If one wheel wants to spin faster than the other, it must first overpower the clutch. The stiffness of the springs combined with the friction of the clutch determine how much torque it takes to overpower it.

Getting back to the situation in which one drive wheel is on the ice and the other one has good traction: With this limited slip differential, even though the wheel on the ice is not able to transmit much torque to the ground, the other wheel will still get the torque it needs to move. The torque supplied to the wheel not on the ice is equal to the amount of torque it takes to overpower the clutches. The result is that you can move forward, although still not with the full power of your car.
-from how thingswork

so they are nothing like traction control

so i was right?

 

Traction control can be done in different ways. You can apply brakes to the spinning wheel, you can cut engine power so you can't break traction, or you can divert the power from the engine to a different wheel that has grip.

The LSD is a mechanical form of "traction control." No sensors, no computers, just a mechanical device that won't let one of your drive wheels spin freely.

 

Didn't you see the subaru commercial with Crocadile Dundee? "It transfers power from the wheels that slip, to the wheels that grip!"

I still remember the animated diagram...

silly consumers...

-Rage

 

LSD helps courning and take offs. more power to the ground in curtian situations.

 

To give you hallucinations.

Oh that LSD. With an open differential, the power always goes to the wheel with the least resistance. For example, if you had one of the driving wheels on ice and the other on dry pavement...flooring it will only make the wheel on ice spin. An LSD on the other hand would transfer some of that power to the wheel with greater traction.

Now think about turning a hard left, the passenger side wheel (right wheel) would have greater traction as well as greater impact on guiding the car in the direction you want to turn. So having the right wheel spin would be more advantageous then spinning the left (inside wheel) which is barely getting any traction

 

life sux d``` j/k

 

great explanation tommy

 

It's not a traction control. It's just for preventing the outer driven wheel loose power delivery capability (to the road) when the inner wheel is lifted up and spinning...(in a corner), which is what's happening with a normal diff....

http://www.howstuffworks.com/differential.htm
Read all pages and you will understand. Traction control works on all driven wheels and controls the engine power output. LSD does not control the engine power output.


[Modified by DutchITR1689, 12:04 PM 10/9/2002]

 

so how do u know if u have an LSD ?

 

If you see pink elephants dancing on your ceiling you have LSD !

 

1) Trust the constructor

2) Take a corner with you R at RELATIVLY high speed and take the same
corner with a car without LSD and you'll really feel the difference...

 

My GOD..talk about tossing explanations…wow..

I hope you’re not more confused than before you asked the question.

The reason cars have a differentials is so that each driven wheel can be allowed to spin at different speeds from each other. This enables stability in a corner because the inner wheel has less distance to travel, it will have to turn slower than the outer wheel to enable the car to track the corner. The diff allows this to happen.

NOW…the bad side effect of a differential is its tendency to equalize the torque between left and right shafts. This is good in a straight line but in a corner where the weight is transfered to the outer wheel, the inner wheel has MUCH less traction hence cannot handle the same torque as the outer wheel and will spin. The confusing thing is people think that the inner wheel spinning and traction-loss is as a result of the differential but it is in fact the result of less traction due to weight transfer since the torque on the inner AND output shafts are THE SAME.
The Limited Slip Diff simply and temporarily locks the two shafts together preventing the inner wheel from spinning in effect allowing the torque to be transfer to the wheel with the most grip (i.e. the outer wheel) allowing harder acceleration in the corner. Under normal driving, it has no special effect.

Hope this helps.
I will be expecting and willing to answer any other questions.

BTW I’m a mechanical engineer by profession

 

Good Post.

 

I like bull fights on acid

 

Good post Erotic-R
However are you sure that the LSD actually "locks" the two shafts together ? I would tend to beleive that the LSD would partially lock the two shaft together allowing slippage (ence the name) so that the outer wheel still spins faster then the inner wheel.


[Modified by JPP, 11:42 AM 10/9/2002]

 

LSD restricts the motion of the faster spinning wheel, slows it down (thru clutch friction and spring stiffness) so that it spins at the same speed as the other wheel.

At a corner, the inside wheel is more likely to loose traction and spin faster because of weight transfer. LSD would then engage, slow the inside wheel down, and split the torque between the 2 drive wheels at a certain % difference.

Power is a function of rotating speed and torque. So with same rotating speed on the left and right wheels, but with different torque applied to them, the power would be different. This difference in power on the left and right wheel would create a couple and help the car to rotate (yaw).

With a high locking ratio LSD, the left and right torque differential would be high. Thus the couple that rotate the car would be bigger. But a big drawback is that, if you are going slow enough, the inside wheel does not loose traction, then the outside wheel would be spinning faster than the inside one (travels a longer distance within the same period of time). Then since LSD has no brain, it would do the wrong thing and restrict the motion of the outside wheel ---- hence understeer. That why people say aggressive LSD makes it very hard to drive on the street cuz it's constantly locking the "wrong wheel" at slow speed.

The stock LSD on the type R doesn't have much problem because it's not aggressive. The effect of LSD would be overpowered when the applied torque to the faster spinning wheel exceeds that of the slower spinning wheel. Since the stock unit has a small locking %, it doesn't take much to overpower it.

 

Good point. Perhaps 'lock' is not the best word.
Thank you for pointing that out. The correct work is Restrict as is stated in the previous post. It however doesn't 'permit' wheel spin it just partially restricts it or 'limiting' it.



[Modified by erottik-R, 10:53 AM 10/9/2002]

 

this is slightly misleading - the ITR has a torsen helical limited slip differential - ie it uses helical cut gears and dog gears to provide the limited slip action. There are NO clutches or springs at all. Open up your helms, and read the chapter on the differential...
although exactly how it works is not really important - what is important is that the torsen type differential in the R does not require rebuilding or adjustment. It either works or it doesn't.