As I understand it, the limited slip differential keeps equal power applied to both wheels at all times, as opposed to one wheel applying more power than the other, during cornering, etc. I was just curious about HOW MUCH of a difference the LSD makes in 1/4 times. Have any of you seen any figures for 1/4 times for a teg with/and or without LSD ? Is the time difference on the quarter mile really worth the price of an LSD ?

 

Depends on the LSD. I can't remember the names right off the bat, but there are LSDs (kazaa?) that primarily improve turning/handling and other LSDs (quaife?) that improve on 1/4 mile times. Almost all the people I know with aftermarket LSDs bought them for the first reason: to improve handling.

Shingo

 

There's a few types: clutch pack, gearset (a.k.a. torque sensing), and viscous coupling.

Kaaz and ATS make clutch type LSD's. I'll steal a bit from Kaaz's website in explaining them since it's a bit complicated.

 

With a normal differential, which a majority of the cars today are factory fitted with, the operation is very basic. The differential simply separates the power from the engine to the two wheels giving the wheel which is simpler to run more power so that the two wheels are running at different speed, thus providing easier turn for the car. But, when the car is turning at higher speeds, the car will tilt to one side, and you hear the squelching sound. The car doesn't tilt as much as you see in the action movies, but tilting still occurs. When this happens, the normal differential puts more power on the wheel that is in the air, which is useless until the car is out of the turn. This is where a KAAZ L.S.D. can help to reduce the loss of power transferred to the wheel.

As you may already know, a race driver wins their race from gaining time when they are cornering. For this reason, many car manufacturers keep trying to make cars turn more efficiently at a faster speed without slipping out of course. The structure of the normal differential is as shown below:



The KAAZ Limited Slip Differential is constructed very similar to the normal differential, as shown below:



As you can see, the side gears, pinion gears and the pinion are all located inside the two pressure rings. Behind each pressure ring are several clutch plates “A” and “B”. When the accelerator is stepped on, the differential case spins and pushes the pinion in between the pressure rings. The pressure rings are then pushed out against the clutch plates making the plates bind together and lock on both drive shafts making both wheels turn at the same speed. The cone spring is installed at the very end of each multi-clutch plates. The cone springs apply some initial torque to the plates so that the pinion doesn’t need to be pushed too far to make the L.S.D. come into effect.

Sometimes you will hear these terms used in the business of L.S.D. trading and the racing department, etc. but what does it mean? As we mentioned before, when the accelerator is stepped on, the L.S.D. comes into use. But what if you are braking through a turn? 1-Way L.S.D. means that only when the accelerator is stepped on, the L.S.D. comes into use. The 1.5-Way L.S.D. means that when the car is braking, there is little L.S.D. effect and the 2-Way L.S.D. means that either when the car is accelerating or braking the L.S.D. is always active. The difference between these are the shaping of the cam into different shapes for the pinion to fit. The diagram below shows how the 2-way version of the Kaaz L.S.D. operates.

 

Both Quaife and the OEM Honda LSD are what we call torque sensing or Torsen differentials. They use gears instead of clutches. The essential difference between a gear-type and clutch-type diff is that a gear-type never locks. An open differential (a.k.a. standard) always sends more power to the wheel with less traction, similarly to how electricity follows the path of least resistance. A Torsen differential acts exactly the opposite. More power is sent to the wheel with more traction. Quaife gives that overly simplified explanation, and Torsen has a physics paper on the subject here.

 

The final type of LSD is a viscous coupling. Generally you won't find these in the aftermarket but in OEM applications. Nissan uses them pretty extensively as does Subaru. From howstuffworks.com:

The viscous coupling has two sets of plates inside a sealed housing that is filled with a thick fluid, as shown in below. One set of plates is connected to each output shaft. Under normal conditions, both sets of plates and the viscous fluid spin at the same speed. When one set of wheels tries to spin faster, perhaps because it is slipping, the set of plates corresponding to those wheels spins faster than the other. The viscous fluid, stuck between the plates, tries to catch up with the faster disks, dragging the slower disks along. This transfers more torque to the slower moving wheels -- the wheels that are not slipping.

When a car is turning, the difference in speed between the wheels is not as large as when one wheel is slipping. The faster the plates are spinning relative to each other, the more torque the viscous coupling transfers. The coupling does not interfere with turns because the amount of torque transferred during a turn is so small. However, this also highlights a disadvantage of the viscous coupling: No torque transfer will occur until a wheel actually starts slipping.

 

Links

Howstuffworks.com - How differentials work
Active Traction Service Japan
Kaaz USA
Quaife America
Zexel Torsen Inc.

 

Thanks alot for the info !!! I was planning on getting an LSD for my b18c, but I wanted one that would improve 1/4 mile times.......so far it seems that the significant advantages come in the form of improved handling, but 1/4 mile times arent impacted as much.

 

An LSD helps with traction. If you stomp the gas and spin your wheels, whichever wheel has less traction will be sent more power by the stock differential. With an LSD, the available traction is more fully used. So you'll get a better 60 ft. time which translates into a better 1/4 mile time. Once again, it's only a few tenths, but you have to weigh the price, etc...

Now since you've been posting a lot on various things that you might get which will help with your 1/4 time, I suggest starting a new thread like this:

"I have x amount of money to spend and I want to run x in the 1/4 on (pick one: street or slick) tires. What are some ways I could do so?"

 

An LSD will help with your 60 ft. times. But it's not going to be that huge of a difference. There are better ways to spend your money on if 1/4 mile times are all you care about. Most of the LSD's impact will be felt during corners, turns, etc.

I drive a Nissan Maxima that's supercharged and nitroused. We recently put in a custom built LSD, I prototyped it for IPT. It's a clutch pack type unit with 50-50 split at full lockup. Honestly, after getting it installed, I would never go back to an open diff. The handling of the car is so much improved. No more smoking the inside tire coming out of a hard corner. But on the launch, it doesn't make as huge of a difference. The car does launch noticably harder, and there is more wheelhop. But it's not a night and day thing. I'm going back to the track in 10 days, so we'll see if the 60 ft. time drops.