I don't have much of opinion really, but perhaps some of us would like to discuss and point things out and maybe we could then bury this subject for good after one good discussion so discuss, no flaming and no blaiming, back up your arguments with something and so on, have a nice discussion
Yeah, diffs are definately working right other than the missing preload in the clutch pack. I think it's in the tyre physics like Scawen said, that we can use the locked better. You have to set the suspension (springs and anti-rolls) so that the inside driven wheel would lift off the ground while turning (meaning stiffer front suspension on an fwd, and stiffer rear suspension on an rwd than on the other end of the car), and like that you can avoid the crazy understeering effect of the locked-together wheels, so you can turn well enough. I suppose the tires can take on much more weight than they should be able in real life. Let's say the FZR is rear weighted as it is, and with stiffer rear suspension the outside rear tire holds almost the whole rear weight of the car while turing, and with downforce as well that is a lot of kgs, which would cause massive tire overload, and a loss of grip, but not so much in LFS. So yeah, its probably in the tires.
But I think adding preload to cluch pack would make it a hell of a lot better, and as it's alrealy faster (but a lot harder to drive) in some cases it would make the drivers use that already, and a couple of shaping in the tire physics would make everything right: locked diff => off road :P
I do diff preload in my sim and quite frankly there's not a whole lot of difference between having it and not having it. There are some subtle things like stability under braking being improved a little bit, but it's not very noticeable. The scenarios bought up on this subject are under full cornering. In these situations the torque bias ratio is overpowering the preload anyway which often completely nullifies its effect so long as you don't have really tremendous weight transfer across the axle.
An LSD is applying torque to each wheel in an attempt to lock them together like a clutch. Preload is very easy to model. All you do is calculate the locking torque between the wheels on that axle given their input torques and the locking percentage or torque bias ratio, which seems to me is already done in LFS properly and is fairly straightforward. Preload just says that there's a certain minimum amount of torque that will always be applied. If the locking torque from the torque bias ratio/locking percentage ends up being smaller than the preload torque, you use the preload torque instead. Outside of the preload torque envelope (when locking torque is greater than the preload) the preload has 0 effect, such as in hard cornering. You use one torque or the other, not both at the same time.
A locked axle is not tough to model. All you pretty much have to do is make sure both tires are turning the same speed. That'd be pretty hard to get wrong, especially if you treat the entire thing as a single rotating object.
I haven't tried a FWD in my sim in years, certainly not with the current model, so couldn't comment on whether it behaves the same way. If there's something a bit off though it's probably in the tires indeed. Mine feels somehow a bit different to drive than LFS, likely because of the tire model. Combined slip modelling probably has a lot to do with it and becomes rather important to get right with a locked axle. I can run around with a locked axle in my deal all day long and it doesn't suddenly turn into snap oversteer under throttle everywhere (RWD), even with generous power, no downforce, and so-so tires. It's just not as critical in my model for some reason.
If I were to look for a problem here it'd be in the combined slip workings of the tire model first. It's very good now and vastly improved since a year ago, but perhaps not quite 100% on just yet. I could be wrong though
That is exactly what we're talking about when saying the LFS clutch pack doesn't work well.
You go through a corner, about 0g longitudinal acceleration, the car tries to oversteer away. In LFS it's a good strategy to apply 30-40% throttle now, because as soon as you do that the rear wheels find grip and the car turns properly.
That is a typical LFS driving technique. What you do there is you force the diff into locking under power, which encourages understeer.
The same thing happens in slower corners while lifting from the brakes. Under coast the diff is locked, you approach the apex and as soon as you leave the brakes the car tries to oversteer, but as soon as you apply throttle the oversteer is gone, because the diff is under power-locking.
It is a very tedious behaviour and promotes all kinds of weird driving techniques. The basic thought when driving a clutch pack diff in LFS always is "Never, ever, operate the diff between coast and power or you'll oversteer."
To my understanding that is the case when preload is either non-existant or very very low.
I tried to circumvent this so very often by trying out everything with the setups and I can't avoid that problem with the clutch pack diff.
What Vain says seem to be then why I feel myself incompatible with clutch pack diff as when I drive it it feels to be all over the place, but I believe there is much more to it too as my troubles driving it come worse when I increase locking %, perhaps I just suck at driving which is most likely.
Viscous diff however seem to be less violent as well is locked diff too, but that is about everything I have looked into this and I have no idea does things work right or not.
When other rear tire get to air in RWD with clutch pack it seem to rev quite freely, it is annoying but I guess that is how it is then?
Exactly. If anyone wants to see this effect just give the MRT a go with the clutch pack diff.
What I wonder is what is the underlying reason for this effect? Why do LFS cars have to rely so strongly on the diff to stop oversteering? Getting a car to handle well shouldn't be too difficult with a real car. I'm guessing there are still some problems with the tyre physics (as I assume that the rest of the physics should be understood well enough to be free of errors) but I can't pinpoint what would need to change to improve this.
