LSD (Limited Slip Differential) Q&A, stock and aftermarket!

[dp1]

Originally Posted by SubieNate

I know lotus refuses to put any kind of LSD into their cars as they believe they interfere with cornering. What's with that?

Some loti have LSD

[DougW]

So now that we all agree a LSD is good thing who makes the best one and at what price?
DougW

[DriftEm]

Hey Mike, how is Quaife ATB Differential different than the stock torsen type?

[SubieNate]

Originally Posted by dp1

Some loti have LSD

Which?

[xwd]

Lotus added the LSDs at least to US Elises/Exiges later on. They traditionally didn't because the Elise/Exige have a lot of weight in the rear of the car, do not use a rear swaybar, and have a more advanced and well-tuned suspension. The story is they added them for US people autocrossing the Elise because autocrosses have tighter corners. On a track Lotus still says all the LSD will do is make you slower. We aren't driving Lotus cars...

All LSDs add some parasitic loss because the moving assemblies are heavier. Some clutch type LSDs weigh a lot and clutches always add parasitic loss, but it's nothing really in the grand scheme of things.

Quaife and stock Torsen work the same way but different internals to get there. They both multiply torque from the spinning wheel to the wheel that isn't spinning.

I had a 1.5-way Kaaz LSD in the rear of my WRX and 1-way Cusco mechanical LSD in front. It made a huge difference. The Cusco Type-RS is a "Salisbury" type LSD which is mechanical but acts like a clutch type LSD. The Kaaz LSD was super noisy at low speed, but it worked. It probably needed a little less abrupt lockup but I never got around to changing it.

My Jeep Rubicon has "locking" diffs. In 4WD mode with the diffs locked the turning radius is huuuuuuuge. You don't want the wheels turning the same speed all the time.

I'd use an OSG in this car or the Guard Transmission one, but the Guard one is probably at least 2x the cost of the OSG which is already one the higher priced LSDs.

[CSG Mike]

Originally Posted by DriftEm

Hey Mike, how is Quaife ATB Differential different than the stock torsen type?

How it works is different, but the end result is the same. It needs resistance on both wheels to work, and once one wheel spins, it's effectively open.

[CSG Mike]

Originally Posted by DougW

So now that we all agree a LSD is good thing who makes the best one and at what price?
DougW

The Cusco and OS-Giken units are the most popular choices down here. We carry and configure both.

The Cusco RS is 1520, while the OSG is 1690.

[Poodles]

Originally Posted by CSG Mike

It sounds like you had a badly matched LSD for whatever car you drove. A properly matched and tuned LSD will feel exactly how you described a Torsen, but more progressive, and more effective.

As with suspension tuning, you can't just blindly throw on parts, and expect it to improve your car.

Both were factory parts. But the inherent difference between a clutch type and a torsen is that the clutch is "dumb" and will fight any difference in the speeds of the axles while the torsen acts as an open diff until slip happens. Usually why people feel clutch types "push"


Then again, that's only for spring based LSDs (which mine was) and not for ramp styles which is where I would put most performance clutch types into.


As it is, the only weird "bad" LSD I've driven is an old Miata viscous. Then again they're known for being essentially an open diff after 60K miles.


LSD's are a bit subjective and what's best is often opinion (so long as they're actually functioning). Of note, many very high end cars have run torsens (McLaren F1 ran a torsen, GTRs run them, Audi, etc).


Interesting subject

[Quentin]

"- You will not suddenly spin if you suffer loss of traction on just one side of the vehicle"

You should probably clarify that you are talking about spinning a tire... and not the car. Haha

So, what are the downsides of aftermarket LSDs? Cost, required tuning, etc? I've found that it is pretty rare that there is a no compromise choice out there.

[mid_life_crisis]

Originally Posted by SubieNate

I know lotus refuses to put any kind of LSD into their cars as they believe they interfere with cornering. What's with that?

Think of the last time you pulled out of a sidestreet where the roads were clean and the turn was sharp. If you had an LSD, one tire probably chirped because they needed to spin at such different speeds and the LSD wouldn't let them. In short, on a really tight turn, an LSD can induce a loss of traction to one tire. This is why for many years only off-roaders and drag racers used them.

[7thgear]

Hi Mike


can you add to your original post the real world effects of 1, 1.5 and 2.0 LSD? Like, how do they affect corner/exit approach and inputs.

[xwd]

Cusco and ATS have some good diagrams and whatnot on 1-way, 1.5-way, and 2-way LSDs. Matt from Guard did a good writeup on either here or NASIOC on what it really means but I can't seem to find it now. They don't use those terms, they consider them made up by the JDM brands as a simplified way to describe the operation.