Why you need a LSD if you like cornering!

[Moto-P]

Originally Posted by DougW

So which LSD works best for the price Wavetrac has both a torsen and clutch type together maybe making the best or the worst of both worlds?.
DougW

If one has a clutch type, there isn't really a need for a Torsen to be mixed into it. It may help prolong the life of the clutch, but you also lose all the merits of a pure clutch system by introducing yet more variables in the setup, as well as complexities associated with the dual-pack system like that... Maybe it's good for those who STILL don't want the added maintenance, but... I personally prefer that if I am spending couple grand on the entire swap-over to gain control of a sports car, I would like it to be simple, predictable, and capable of it to be tuned very accurately.

[Captain Snooze]

expletive!expletive!expletive! compromises!

[blackhawkdown]

the wealth of knowledge in this thread alone is epic.

[whataboutbob]

Originally Posted by 7thgear

I'd like to think that I have decent car control skills, but I've never really been able to dictate the car's movements to the extent that is expressed in this video


what makes this car handle the tight corners the way it does, is it raw power? e-brake pulls? Diff magic? Or some of that driver special sauce that only the Finns seems to have

dude, that was AWESOME! Esp the jumps!

[Captain Snooze]

I kind of understand/appreciate what a clutch diff will do coming out of bends on the power but I don't get what the (1.5-2 way) diff will be doing under brakes whilst cornering. Would some one be so kind as to explain the benefit?

[whataboutbob]

I'm not an expert, but I believe a 2 way has symmetric ramps for acceleration and braking, and the 1.5 has a different ramp profile for acceleration and braking.

[Captain Snooze]

Originally Posted by whataboutbob

I'm not an expert, but I believe a 2 way has symmetric ramps for acceleration and braking, and the 1.5 has a different ramp profile for acceleration and braking.

Sure, understood but I'm wanting to know what this does for performance.

[Superstar]

As always, appreciate the data and the explanation.

Now show me the laptimes and then take my money

[diss7]

Originally Posted by Captain Snooze

I kind of understand/appreciate what a clutch diff will do coming out of bends on the power but I don't get what the (1.5-2 way) diff will be doing under brakes whilst cornering. Would some one be so kind as to explain the benefit?

The difference is entirely on the decel side.
A locked diff is always locked.
A 2way locks up as quick under decel as it does under accel. It's not ideal for circuit, it's more for drifting.
There's a couple of guys in NZ that put 2ways in their cars and use it for circuit. As they get more confident with braking and start to threshold brake, they start spinning their cars.
On the street, I think a 2way is a bit dangerous unless you really understand the diff. Put it this way, I came around a corner around our hills, and there was some unforeseen road works. Because of the way the 2way works, when one wheel slipped, it locked the diff, it had the same effect as pulling the handbrake. That was not under any braking, just engine braking. I was just lucky that I've done enough drifting that my immediate instinct was to get on the power, not the brake.

A 1.5way still has the ability for the diff to lockup in this manner, but the 1.5 means that the decel lockinng/ramp is 50% of the accel. So it would take more for lock up to occur under decel.

A better way to understand these diffs is
A 2 way is a diff where if the accel lockup is seen as the strength of 1.0, the decel lockup is also 1.0. 1.0+1.0=2.0 eg 2way

A 1.5 way is as above, but the decel ramp is only half of accel. So 1.0+0.5=1.5 way.

Finally a 1 way will never lock under decel. So 1.0+0 =1 way.

So couple more things
Those three different "way" diff types all act the same under accel, it's only the decel ramp up rate proportionate to the accel rate that changes.
So all you need to ask yourself is how you want it to lock up under decel (if any)
As I've said a couple of times, I would most likely run a 1way if all I did was circuit racing. Maybe a 1.5, but certainly not a 2way.

I just think of those times when I don't want the rear locking up, and that is under heavy braking and turning into a corner.

I think a lot of the confusion with these diffs comes from the 2.0 is a bigger number than 1.5, so it must be better. Eg people thinking of it like stage 1, stage 1.5 etc.

But it has nothing to do with that at all. It's entirely to do with how much decel ramp up you want proportionate to the accel, either the same, not as much, or not at all. And I'd say most people don't want much (or any) decel lock up at all.

Finally, you can still drift with a 1.5 or 1 way. They'll both still lockup the same under power as a 2 way. It's just it's a bit harder with a 1.5 to initiate a feint (or other 'slowing down' or decel) type drift; and a 1 way won't do it at all. But given the way drifting and particularly FD have become sideways drag racing, you could probably compete in high level drifting even with a 1way.

But you'll learn more with a 2way, especially in a low power, low tyre grip car like the gt86.

In short
2way - for drifters
1.5way - good all rounder, compromise between 2 and 1. Could be used for circuit.
1way - my choice for circuit. All a drag racer needs as well. Get this one of you never want lockup under decel.

[Captain Snooze]

Originally Posted by diss7

The difference is entirely on the decel side.
A locked diff is always locked.
...............
In short
2way - for drifters
1.5way - good all rounder, compromise between 2 and 1. Could be used for circuit.
1way - my choice for circuit. All a drag racer needs as well. Get this one of you never want lockup under decel.

Thank you for the detailed reply but it still hasn't answered what I was trying to find out. That is, what is the benefit of a 1.5-2 way. What effect does it have on the car/steering under brakes. I get that a lsd is about getting the power down to the slipping wheel but what does this mean under braking? I understand the technical detail but not the application.

[diss7]

Originally Posted by Captain Snooze

Thank you for the detailed reply but it still hasn't answered what I was trying to find out. That is, what is the benefit of a 1.5-2 way. What effect does it have on the car/steering under brakes. I get that a lsd is about getting the power down to the slipping wheel but what does this mean under braking? I understand the technical detail but not the application.

Under braking in a straight line it means nothing. Because both the rear wheels are turning at the same speed.

But add in a corner to the braking situation and this is where the differences are
In the corner the wheels are now spinning at different speeds.
As you brake, the 2 way isn't going to be very tolerant of the wheels spinning at these different speeds, so will lock the diff. This means the outside wheel will partially slip as it is forced to only spin at the same speed as the inside wheel. Or the inside wheel will have to skip and bounce so that it can spin the same speed as the outside wheel. Or most likely a mixture of the two.
Either way, it's a loss of rear traction, the last thing you want when threshold braking I'm a circuit car. It will likely induce a spin or big oversteer.

A 1.5 way will be more tolerant of these different wheels speeds so this point won't be reached as quickly.

This is also where the ramp up of the diff comes into play. You may have the ramp up set at a point so that this point with a 1.5 under decel isn't actually reached for a certain corner angle. Which is what csgmike was talking about when he said that a lot of the chatter and binding can be eliminated by not setting the diff up so tight.

[diss7]

Lsds aren't about getting power down (well they are) they are estentially about how tolerant you want the diff to be with regards to its primary function, that is allowing the rear wheels to spin at different speeds.

Sometimes you want them to be able to, sometimes you don't.
Most of the time you don't want them locked, and only really want it locked when you want to get more power down than one tyre is able to on its own.

[Captain Snooze]

Am I correct in saying that a 1.5 improves braking? My reasoning as follows: Foot on brake, equal braking force to the rear. But the inside wheel is somewhat unloaded compared to outside wheel so the inside wheel has a tendency to lock. So the diff prevents the inside wheel from locking up under brakes around bends.
Is this correct?

(Ffs. My shopping list isn't getting any shorter.)

[diss7]

Originally Posted by Captain Snooze

Am I correct in saying that a 1.5 improves braking? My reasoning as follows: Foot on brake, equal braking force to the rear. But the inside wheel is somewhat unloaded compared to outside wheel so the inside wheel has a tendency to lock. So the diff prevents the inside wheel from locking up under brakes around bends.
Is this correct?

(Ffs. My shopping list isn't getting any shorter.)

Sound logic. And I can think of arguements fore and against; but it boils down to me not knowing to be honest. So will leave for someone with more circuit-based track experience to answer.

It would also lead me to think that you're onto something, as circuit guys seem to favour 1.5 over a 1, and this is possibly the reason why.