LSD For Racing Applications

[sworxx]

I was considering upgrading to an LSD for a race car. I predominantly race on road courses and would really like to get rid of the inside wheel spin. I just wanted to see if anyone out here has one, what kind and what your experience is. I was considering a 1.5 Way KAAZ or a 2 Way set at 80% as my wife also uses the car for Driver's Ed. How drastic is the change from open diff to LSD? I appreciate any input. Thanks.

[~4N~]

For road racing, I'd recommend a helical, or a 1.5-way. The change can be felt the most during sharp low-speed turns, how drastic it will be depends on what LSD you decide to buy. I wouldn't go with a 2-way, since your wife uses the car for driver's ed, she might get some weird looks if her wheels squeal when she turns.

[EazyBreazy]

many will tell you that for a purely road race car, a helical will be the most optimal diff to use as it transfers the power to the wheel with the most grip, instead of locking and spinning both (1.5 and 2 way), or spinning the inside(open)

[elgarvo616]

wait wait wait. your wife uses your track car for drivers ed???

[Pho King]

Dang...those kids are going to be handling it up.

[whiterps13]

Yeah, WTF?

I wish I had drivers ed with her...

[R6_240sx]

I was considering upgrading to an LSD for a race car. I predominantly race on road courses and would really like to get rid of the inside wheel spin. I just wanted to see if anyone out here has one, what kind and what your experience is. I was considering a 1.5 Way KAAZ or a 2 Way set at 80% as my wife also uses the car for Driver's Ed. How drastic is the change from open diff to LSD? I appreciate any input. Thanks.

many will tell you that for a purely road race car, a helical will be the most optimal diff to use as it transfers the power to the wheel with the most grip, instead of locking and spinning both (1.5 and 2 way), or spinning the inside(open)

UHhhh don't u want the inside wheel to spin?

[S3t0_S13]

i feel like learning how 2 drive again

[LayNLow240]

UHhhh don't u want the inside wheel to spin?

if he wanted the inside wheel to spin why would he upgrade from an open diff? generally you want BOTH wheels to grip on all corners. a spinning tire = less traction = bad(well maybe not bad, but they wont be better than one with all traction) lap times.and yeah what the hell.. why are kids learning to drive on a race car? not sure how i feel on that. but cool.

[S3t0_S13]

im in the market for a LSD as well, isnt 1.5 better then 2way in deceleration, since it dosent lock up and have both spinning as full in power as a 2way?

[R6_240sx]

if he wanted the inside wheel to spin why would he upgrade from an open diff? generally you want BOTH wheels to grip on all corners. a spinning tire = less traction = bad(well maybe not bad, but they wont be better than one with all traction) lap times.and yeah what the hell.. why are kids learning to drive on a race car? not sure how i feel on that. but cool.

Yeah i understand what ur saying but he's saying inside wheel spin? That's not even possible on an Open Diff, cuz on an open its the outside wheel where all the power is going too.

[S3t0_S13]

i think he means the free spinning of it when its a open diff?

[AmoebAssassin]

A helical is great for a road car because it is silent and smooth in operation. If your wife is using the car to teach new drivers, get a helical.

However, for a road racing car, I'd recommend a clutch type differential. People assume that a helical has the capability to infinitely bias torque between the drive wheels; this is not the case. Once you exceed the maximum frictional force between the planetary gearset and the differential housing, the torsen will not be able to bias any more torque. For high power track cars, this limit is far below the amount of torque being delivered to each wheel, and the diff will act like an open diff.

A clutch type diff can support a fully even torque distribution between the drive wheels, or at least fully even minus the breakaway torque rating of the diff. Additionally, clutch differentials will be more predictable than a helical diff, which will bias torque based on surface roughness, tire temperature, rear tire slip angle, among a number of other factors that affect the amount of traction each tire can provide. In racing, while it is great to be able to turn hot laps, consistency is the name of the game: this is where clutch diffs shine.

Most pro road race cars will run a spool or a 2-way. Idiots will tell you that this causes understeer, but since you are building a race car, im sure you're knowledgeable enough to know how to tune out understeer using roll bars and/or roll center adjustment.

Idiots will also tell you that clutch diffs will cause your tires to spin or wear faster, but good drivers have good throttle control and will be able to regulate wheelspin. And I doubt tire wear is that big of a concern if you're choosing to build a track car.

I'd analyze your driving style and decide between a 1.5way or a 2way clutch diff.

-Neel

[S3t0_S13]

hmmm, thats a pretty good explanation, answered most of my questions buddy, i was looking at OBX on ebay, people dont reccomend those, im going for the S15 OEM helicals, i really want quiet, better then open diff, once a blue moon track running, occasional burnout/donuting diff setup. Am i looking at a helical?

how long do these last? does oil need to be chnaged very often?

[574-240sx]

A helical is great for a road car because it is silent and smooth in operation. If your wife is using the car to teach new drivers, get a helical.

However, for a road racing car, I'd recommend a clutch type differential. People assume that a helical has the capability to infinitely bias torque between the drive wheels; this is not the case. Once you exceed the maximum frictional force between the planetary gearset and the differential housing, the torsen will not be able to bias any more torque. For high power track cars, this limit is far below the amount of torque being delivered to each wheel, and the diff will act like an open diff.

A clutch type diff can support a fully even torque distribution between the drive wheels, or at least fully even minus the breakaway torque rating of the diff. Additionally, clutch differentials will be more predictable than a helical diff, which will bias torque based on surface roughness, tire temperature, rear tire slip angle, among a number of other factors that affect the amount of traction each tire can provide. In racing, while it is great to be able to turn hot laps, consistency is the name of the game: this is where clutch diffs shine.

Most pro road race cars will run a spool or a 2-way. Idiots will tell you that this causes understeer, but since you are building a race car, im sure you're knowledgeable enough to know how to tune out understeer using roll bars and/or roll center adjustment.

Idiots will also tell you that clutch diffs will cause your tires to spin or wear faster, but good drivers have good throttle control and will be able to regulate wheelspin. And I doubt tire wear is that big of a concern if you're choosing to build a track car.

I'd analyze your driving style and decide between a 1.5way or a 2way clutch diff.

-Neel

finally someone that knows what they are talking about. I was getting pissed off and going to say 2way or spool but I have only ever seen 1 spool in a 240 before. There was an article not too long ago, I can't remember where I seen it. I'm going to look for it.

[LayNLow240]

Yeah i understand what ur saying but he's saying inside wheel spin? That's not even possible on an Open Diff, cuz on an open its the outside wheel where all the power is going too.

an open diff is like electricty. it takes the path of least resistance. on the exit of a corner, alot of the cars weight is on the outside of the turn, meaning the outside wheel has the most traction and the inside has the least. the inside, being easier to turn, will be the one that gets all the power because it has less traction than the outside wheel. its like trying to do a burnout with one wheel on cement/asphalt/something with traction and the other on ice, youll just spin the one thats on the ice.

finally someone that knows what they are talking about. I was getting pissed off and going to say 2way or spool but I have only ever seen 1 spool in a 240 before. There was an article not too long ago, I can't remember where I seen it. I'm going to look for it.

alot of 240's run with a spool, see all these threads talking about people wanting to weld their diff and others saying they have done it, its nice, etc. a welded diff is basically a spool.

[AmoebAssassin]

hmmm, thats a pretty good explanation, answered most of my questions buddy, i was looking at OBX on ebay, people dont reccomend those, im going for the S15 OEM helicals, i really want quiet, better then open diff, once a blue moon track running, occasional burnout/donuting diff setup. Am i looking at a helical?

how long do these last? does oil need to be chnaged very often?

Yes, the helical is your best bet for a street car that sees occasional track duty.

You'll find a helical much more rewarding for a predominantly street car because your car won't chatter, hop, or drag tire around low speed turns, and you'll still enjoy torque biasing at the power levels you're likely to make.

Change the diff oil whenever you change your trans oil, or sooner. I change it once every two drift or track days, because clutch diffs will wear metal into the fluid as the plates wear down.

A helical will last forever if there are no manufacturing defects in it. None of the moving parts are wear items, so the diff will last quite some time. I'd suggest the S15 unit over the OBX. It's pricier but you really can't beat OEM fit and finish for cheaper.

[SeVa-S13]

alot of 240's run with a spool, see all these threads talking about people wanting to weld their diff and others saying they have done it, its nice, etc. a welded diff is basically a spool.

Just like ebay turbos are basically quality turbos.

And even though it's been covered, HLSD for street cars with track time, Clutch for track cars. (1.5 for me kthx)

Honestly though, if this guy is not only letting his wife drive his 240, but allowing her to teach new drivers in it, he needs a severe beating. Or he needs to get the wife a car.

[R6_240sx]

an open diff is like electricty. it takes the path of least resistance. on the exit of a corner, alot of the cars weight is on the outside of the turn, meaning the outside wheel has the most traction and the inside has the least. the inside, being easier to turn, will be the one that gets all the power because it has less traction than the outside wheel. its like trying to do a burnout with one wheel on cement/asphalt/something with traction and the other on ice, youll just spin the one thats on the ice.

I get what ur saying with least resistance and when ur turning hard the least resistance is in the inside wheel since its lifted off the ground. But isn't it when ur tire breaks traction the outer wheel will be spinning the fastest (in an Open) since it has the least amount of resistance?

Well anyways he should've just put instead of saying, "i want to get rid of the inside wheel spin" i want to get my power down to the ground. Because there are occasions where u will get inside wheel spin, due to hard cornering, or outer wheel spin from breaking traction.

[nismofly]

all a torque biasing differential does is split torque delivered to each wheel proportionally to the amount of frictional force(grip) at each wheel.

so If 60% of the available grip is at the outside tire, the outside tire will receive 60% of the total torque generated by the car, and the inside will of course get the other 40%

It doesn't matter how much torque the car is making, the diff will still function in the same way, because there will be more internal friction generated in the differential. You can't ever "exceed the limits" of a torque biasing differential by having a car that is too powerful. The only way you exceed it's usefulness is if a car is setup in such a way that there is so much load transfer through a corner that the differences between the frictional forces at each wheel becomes very large, and exceeds a certain proportion (the torque biasing ratio, TBR). For example, if you lift the inside wheel while cornering, A Helical differential will transmit all torque to that wheel, because the TBR has been exceeded. But a properly set up RWD car wont lift an inside rear wheel, so you wouldnt need to worry.

However, for a road racing car, I'd recommend a clutch type differential. People assume that a helical has the capability to infinitely bias torque between the drive wheels; this is not the case. Once you exceed the maximum frictional force between the planetary gearset and the differential housing, the torsen will not be able to bias any more torque. For high power track cars, this limit is far below the amount of torque being delivered to each wheel, and the diff will act like an open diff.

There is no maximum frictional force within the differential. The more torque that is generated by the car, the more frictional force there will be, and so it will still function.

I will admit that the TBR might actually change depending on the amount of torque that your car is making, due to the fact that the increase in frictional force inside of the diff might not be 100% linear, but it shouldn't change significantly to really make a difference.

-naed240sx

[sworxx]

I think I need to clarify a few things, I have never seen a larger group jump to bigger conclusions before, it is probably my fault, I should have been more specific.

My wife uses the car for driver's ed. HPDE, High Performance Driving Events. She does not instruct students in the car. Although she plans to go to an Instructor Clinic next year, so look out!

Yes I meant free spinning in the open diff. the wheel does not put any power down, so it I guess it is lack of spin. I was eqautung it to spinning and not doing anything, my bad.

Thanks Neel for a very educated answer, I appreciate all the other suggestions. Very entertaining.

I was leaning towards a Clutch type KAAZ, but was struggling between 1.5 and 2 way. It was suggested I get a 2 way but have it limited to 80%. That was a suggestion from KAAZ, but it will wear quicker.

I know that they say true racers should get a 2-way, but I am not even close to being a "great" racer so I thought a 1.5 way might be better, why do I need it to work as aggressive under braking? Plus like I said, my wife drives it as well, so I don't want it to be really unpredictable under turn in and braking.

I do realize I would need to adjust accordinly to reduce the understeer, I will be working with Koni and their new racing suspension to get it dialed in.

I was hoping to hear from some people that could actually describe what it feels like to drive a 1.5 or 2 way on the track, how big of an adjustments do you have to make in your driving?

Thanks.

[R6_240sx]

2 is probably better, for sum its jus preference, but 1.5 is easier to start off with. I'd probably say for u to get a 1.5 cuz its more forgiving. Best bet is for u 2 find sum1 that has both and see which one u like better.

[Kenny_D]

VLSD FTW!!!!!!!!!!

[RB20DETodd]

Since its for drivers ed i say weld the diff that would be ballin