Why you need a LSD if you like cornering!

[Captain Snooze]

Originally Posted by Ubersuber

Oxymoron

Ok, now you're being pedantic just for the sake of it.

[simpleisbest]

Here's comparison done in the past with GRM:

http://grassrootsmotorsports.com/art...hats-the-diff/

Might help most understand the differences between types of LSDs.

[Ubersuber]

Originally Posted by Captain Snooze

Ok, now you're being pedantic just for the sake of it.

Oxymoronic would have been pedantic, I resisted.

Technically, use of "oxymoron" was colloquial rather than correct useage.

Now I'm being pedantic.

[jvincent]

Working your way towards another ban I see. Carry on.

[cdrazic93]

Havent taken my power mechanics class yet so im still fairly unsure how these work. Never the less...

[wparsons]

Originally Posted by Ubersuber

Oxymoron

No, you're the moron.

Clutch LSD's aren't on/off switches like you're claiming, they only lock as much as needed, and do so progressively. How aggressive they lock can be tuned to suit the driver. You're mixing behaviours between diff types. A true locker fully locks under any throttle, regardless of differential wheel speeds. A clutch LSD only reacts when the wheel speeds are different, and are tunable to control how great the difference in speeds can be before it starts to lock up. It doesn't go fully locked as soon as the speed is slightly different between the wheels.

the clutch type uses friction discs and springs to preload the differential gears so they don’t spin as freely as they would in an open unit. As the axles try to move at differing speeds, the discs or clutches slide against each other, resisting this action. The result is a partially locked-together axle that still allows differential wheelspin.

Like the Kaaz, the OS Giken is also tunable for a variety of speeds and degrees of locking.

The Kaaz limited-slip differential is a variation on the clutch-type theme. When the vehicle is coasting, the internal clutch plates rotate freely without any preload, allowing the differential to act like an open unit. However, applying torque to the differential through either acceleration or braking causes a cone-shaped pressure ring to gradually lock the plates together.

[wparsons]

Originally Posted by ZDan

Every day I feel and hear the Torsen in my s2000 hinder differentiation as I make the 90 degree corner out of my driveway.

I hear/feel this ALL the time in my FRS as well, in tight parking lot turns and even in the parking garage at my office. Any throttle application in a tight turn at very low speeds has the inside tire scratching at the pavement.

[Manji]

Well didn't this thread turn into a bag of d1cks

There is benefit in putting a mechanical lsd in even a stock gt86. Even an average driver can feel it. Drive one with one and one without and you'll see for yourself. Even just on some spirited road driving.

Several of us in NZ had the TRD mechancial 2 way put in as a dealer fitted option. I was one that didn't, and I saw the difference at the track. I then drove one with the mechanical and I felt for myself how much better the car could "spring" out of the corner. (Where as the reality is that it was my car getting held back out of the corner.)

The trd units have the preload set a little high IMO. Great for drifting, but I think it needs to be adjusted, which I plan to do. I actually wished I'd got a 1.5 as I don't mind the accel setting, but wished it was softer on decel as I get push into some corners.

If I didn't already have one, I'd be getting this csg spec'd one, because they've already done the leg work with respect to the settings.

[ZDan]

Only way the stock Torsen would be holding you back is if you're getting inside wheelspin in tight corners or over bumps. On my stock S2000 on RS-3s, I have always gotten power to both wheels at every track I go to with the stock Torsen. And on my street/track FD on Nitto NT01s, I always get power to both wheels at every track I've taken it to with a Torsen T2R ('03/'04 Cobra 8.8 IRS diff). Full dorifto every time

I haven't tracked an FR-S/BRZ. I guess it's possible that with the 54/46 weight distribution it might be possible to lift the inside wheel enough to induce inside rear wheelspin on very slow/tight corners, but I would guess it should only have that problem on quite sticky tires.

Anyone considering a clutch-type should check out the article linked in posts #77 and #114 http://grassrootsmotorsports.com/art...hats-the-diff/. On a well-developed track car presumably on A6s or R6s, they were apparently getting inside wheelspin with the stock Torsen on their S2000. One clutch-type diff gave them a ~0.4 second laptime advantage, definitely a big deal for racing or TT and fun in general. But a different clutch-type gave them only ~.04-second laptime advantage over the stock Torsen and gave dicey handling characteristics, possibly a net disadvantage over the course of a race.

IMO, drivers just getting into tracking and/or driving a stockish car on tires less grippy than DOT R-comps, stock Torsen should be up to it and the ~$1500 for a clutch-type would be better spent on track days and other mods first.

[simpleisbest]

The S2000 used was a NASA TTC car and piloted by Ian Stewart. Street tires if I remember correctly.

[ZDan]

Originally Posted by simpleisbest

The S2000 used was a NASA TTC car and piloted by Ian Stewart. Street tires if I remember correctly.

SCCA T3 car. DOT, yes, but definitely not a street tire... Looks like R6/A6 to me.



And it says "Hoosier" right on the hood and fender...

[simpleisbest]

Ah...that's right. He ran NASA the following year I think in TTC and won, if I remember.

[Ubersuber]

Well, personal remarks notwithstanding there seems now to be a balance in points of view which may be useful to anyone trying to make a decision about ditching the stock Torsen for a clutch type diff.

The two types work completely differently.

Roll stiffness is complicated and not well understood by the casual modifier.

For good examples of what is important consider the 70's rwd stock Euro racers like the BMW 2002 and Alfa GTV which uniformly show the inside FRONT wheel lifting completely off the ground and the 80's VW GTI showing the inside REAR wheel lifting completely off the ground.

If you need to seriously increase roll stiffness at the traction end of the car then the Torsen isn't going to cut it. Trouble is for fwd (or awd for that matter) the Torsen front diff is your only real choice unless you can fit one of the new clever electronic diffs.

Until that drive wheel is lifting the Torsen should be good enough and actually works better than a clutch type lsd. Once you get that rear roll stiffness up to critical level only a clutch type lsd will work properly for you. If you FI this engine then I recommend you do not try to also increase rear roll stiffness but if you do then a mechanical clutch type lsd will be the only solution to your traction issues out of corners.

A 1 way clutch type lsd will work best for a stock motor. If you get into a surfeit of power then a two way diff might work for you.

[Manji]

Originally Posted by Ubersuber

A 1 way clutch type lsd will work best for a stock motor. If you get into a surfeit of power then a two way diff might work for you.

What difference does the amount of power make, as to whether someone needs a diff that locks under decel or not?