s15 helical vs. 1.5 way clutch type lsd

[FlatDrftCJS]

Ok I did the search thingy and found a bunch of info. But most of the info was not pertinent to my question. I wanted to know how these two lsd's (s15 helical, clutch type 1.5 way) differed from each other.

Thanks
Carlo

Disclaimer: I know this forum is full of flamers so keep it out of my thread. All I want is info, not your input on how much of a noob I am or how this is a stupid question.

[skithesteel]

http://auto.howstuffworks.com/differential10.htm
^Torsen = Helical. Start there.

http://auto.howstuffworks.com/differential8.htm
^Basics of clutch-type LSDs.

http://www.zilvia.net/f/showthread.php?t=38598
^More in depth explanation of 1.5 way vs. 2 way etc.

[OptionZero]

When you go around a bend, the outside wheel has to travel a longer distance than the inside wheel...in the same amount of time. If neither wheel breaks traction you don't turn; if one wheel breaks traction it's usually the inside one (weight shifts outside), and you get lots of smoke. Torque naturally goes to the wheel with the least resistance (inside wheel); you don't want that.

The limited slip differential solves this problem, but in different ways.

Helical Diff:
I don't know the exact terms for the internal parts, but what it does, essentially, is detect when the inside wheel starts to lose traction, during which time it will redirect power through a system of planetary gears to the wheel with the most traction, in this case the outside wheel.

By sending torque to the outside wheel, you can spin the outside wheel faster, allowing it to complete its longer course faster than the inside wheel, which is what you want.

This is beneficial in road racing or "grip" because you don't want to go sliding about a corner, you want to rotate the car through it smoothly.

From a personal experience standpoint, the feeling of an HLSD (the s15 one), is similar to a giant invisible hand grabbing your rear end and helping to turn the car when you stomp on the power.

The HLSD only works when there is some load on both wheels, so if you have too stiff a rear end (laterally), you may end up lifting the inside wheel during a turn, so the HLSD cannot function. In this case, you end up with, effectively, an open diff.

Under deceleration an HLSD does nothing IIRC.

Different types of HLSDs send different amount of torque to the outside wheel.

1.5 way diff:
This diff "locks" when it detects slippage, effectively forcing both wheels to travel at the same speed through a turn. This prevents the inside wheel from spinning uselessly and allows power to actually be utilized fully.

Conceptually, this seems inferior to what an HLSD does, because while forcing both wheels to spin at the same speed is better than the inside one spinning uselessly, it is not as good as allowing the outside one to spin faster.

On deceleration it partially locks (hence the "1.5" part of the name. I don't understand this type of differential enough to explain the benefits or drawbacks of locking on deceleration.

The 1.5way diff is a "clutch" type. In general, they require maintenance and upkeep, whereas the S15 HLSD is install and enjoy forever. The 1.5way will likely be noisier, the HLSD is perfectly quiet.

A differential, along with seats and tires, is probably one of the best upgrades you can do for your car.

A used S15 HLSD will run you about $700 depending on shipping, plus labor if you pay someone to put it into your open diff. The clutch type can go from 600-over 1k IIRC, shop around...you can get one used or new.

Search also for s15 HLSD on FreshAlloy, there are some high level discusssions there.

For grip:
HLSD or 1.5way

For drift:
Welded or 2 way

For losers:
VLSD or Phantom Grip

[idiot goes sideways]

was an interresting answer but one thing bothers me,

s15 diff send most torque to the wheel on the outside?

what i know is that the diff work more like an open when it has grip
until one tire start to loose grip, regular the tire on the inside of a corner,

(sorry but i try to translate technical words from german to english)

so when it starts to loose grip the "gears" will start to put some torque to the outer tires but i think not more than on the inner side, probarly less

this is caused of the "gears".......................

DAMN EVERYTIME I TRY TO TRANSLATE TECHNICAL THINGS, IT MAKE IN ENGLISH ABSOLUTE NO SENSE!!!!!!!!

TO TELL THE STORY SHORT, THE HELICAL DIFF LET THE TIRES SPINN AT MOST THE SAME SPEED BUT DOES NOT LOCK 100% LIKE CLUTCH TYPE
THE MOST TORQUE SHOULD BE ON THE INSIDE THE REST ON THE OUTSIDE
(HOW MUCH I DONT KNOW)
THATS WHY ITS HARDER TO DRIFT

i also don`t get why it doesn`t work when one wheel is in the air??

the diff let the tires spin at most the same speed, when the speed between booth tires is different, so why should it not working??

sorry if i`m mistaken, i never drove a s15 lsd but this is theoretical

[OptionZero]

the actual amount of torque sent to the outside wheels is dependent on the design of the differential. I forgot what the % was on the S15 HLSD.

More or less, does it matter? The effect is the most important part- a force that helps you rotate