Just a question: Is the open-diff behavior thought to be realistic or was its development neglected because nobody uses it anyway (exept for UF1-drivers)?
Correct me if I'm wrong - but most production FWDs do have open diffs, right? So which ones of these do rev up like mad in a tight (or even not so tight) turn sending all the enginepower to the inner wheel leaving you almost without any propulsion (is that the word?) and a lot (just way too much) understeer. LFS does exactly this, which I NEVER experienced in RL... and I'm definitely no stranger to chasing FWDs (including a '96 Cinquecento with a very short wheelbase) thru upwards serpentines - fighting against powerundersteer of course, but it's never that hilarious.

Anyone RL experience with a behavior like that?

Every day in my Passat, my Touran, my Polo, and before in my Mazda 323, in an old Honda and basically any fwd car I have driven.

Yes, in most FWD cars when you drive hard.

Uh... i found the open diff in fwd pretty real in lfs; bear in mind that setup and aggressive driving "exaggerate" the understeer of the car. In real life you wouldnt push to the limit as on lfs... or real life racing

Not so long ago i experimented with XFG to match behaviour peugeot 205gr.n in rallycross. It was amazing how with a similar settings the xrg behaved. In fern bay rallycross x it was like racing with the 205 on rallycross. This really showed how good lfs is... power understeer, weight transfers... was really realistic to be a game. Ehrm. A sim.

Yes I also agree. LFS does a fantastic job at simulating open diffs. In real life I have driven many FWD cars that spin the inside wheel. When i owned a Honda Integra Type R with a helical LSD however it really showed up how bad most FWD cars really are.

ok, I finally have to see that I live in a parallel universe or something.

Its not abnormal for a FWD to spin the inside wheel. My dads accord type-r does it, my brothers V6 mondeo does it. Even my sisters ford puma does it

Maybe it depends on how you enter the corner. The inside wheel would be more likely to spin if your throwing it into the corner instead of going smooth and progressive.

Actually, in my mediocre understanding of physics, the inner frontwheel of an FWD is most likely to lift off / spin if you accelerate hard out of a bend. the acceleration moves the weight to the rear, while centripetal-force moves the weight to the outside. result: no weight on front inner wheel.
so far so good. but in my universe this doesn't happen that extremely. most of all not in almost every turn you do or if you just turn in a continuous circle in 1st gear.
and IF it ever happened it would surely not last like a second and the revs wouldn't hit the limiter.

but as I said. maybe that's just in my universe. but luckily i'm not alone there .

http://www.youtube.com/watch?v=FZIHpa5zyPs
http://www.youtube.com/watch?v=TXtmILKF1mg

I think you mean LACK of centripetal force

And I think maybe you're not driving hard enough (which is a good thing on public roads).

When it happens, it can last several seconds (depending on length of turn, radius, speed and vehicle wheel torque), and yes it can hit the rev limiter.

Also, you drive a lot harder in LFS than you do in real life.

My 1988 Nissan Pulsar (sunny) with all of it's 78hp will spin up the inside wheel leaving you going nowhere fast at all. Try to do a standing start with the wheels turn in the wet and you can actually find yourself going nowhere as the inside wheel spins up as if it's nearly in the air.
I've also driven a modified car that matches the FXO for power to weight, 2.0l turbo FWD and it has an open diff. That's an experience. Don't use much throttle unless your going dead straight in that one unless you want to instantly transform the inside tyre from a solid to gas

Quote from tristancliffe :

I think you mean LACK of centripetal force

no, actually I meant centrifugal force.

Quote from tristancliffe :

Also, you drive a lot harder in LFS than you do in real life.

of course I considered that. but even if I go quickish rather than fast on the limit in LFS the inner wheel spins like mad.

I mentioned the 1st-gear-full-throttle-circle... did that with a cinquecento-cookie-box because we had to find a noise. no spin. go do this with the UF1.

and have you seen the vids? don't think they move slow. if you go like this in LFS with an open diff you have constant spin.

I certainly do not compare LFS-driving to my everyday driving. but I also mentioned the uphill serpentines: that's probably THE situation for an inner front-wheel to lose traction... and it does but it's minimal in real life.
guys, I've chased uphill thru bends with squeeling tyres and throttle to the metal... no spin like that.

come to my universe...

Quote from Alric :

Yes I also agree. LFS does a fantastic job at simulating open diffs.

except for one important feedback ... no gear whine when one wheel slips

Quote from Bandit77 :

no, actually I meant centrifugal force.

It is a LACK of centripetal force that causes load transfer, you to slide to the outside, and your milk to fall over whilst cornering.

Centrifugal isn't the cause.

Bandit:- Come to my rallycross universe where mud and gravel makes your life hell with open diffs then!
I see your point, maybe lfs has way more power understeer on open diffs than real life but... setup it's a big point in that, as i sayd before i spent some time to do a set for xfg to match one of a 205gr.n i drived and really it was much fun and very realistic (still we are talking about a game...). Maybe on the less powered cars (Uf1) it wont be so pronounced as 50hp cars... ehrm dont spin too much.
Hmmm now that it comes to mind my sister Y10 it's a clear example of a very underpowered understeer car with a completely wrong setup even for normal driving. So i contraddict myself .
I think you can notice this problem more in high speed turns where the less powered cars shouldnt understeer too much and of course on tarmac! (On mud and gravel, it's a completely different story and here lfs it's really fun)
So yes lfs it's not perfect, but i dont see this as a BIG lfs hole in physics more like something that needs a small small tweak.

Quote from Shotglass :

except for one important feedback ... no gear whine when one wheel slips

Take the XFR out with an open diff, and report back

Any time the trans spins up in LFS, there is gearwhine.

Re main topic:
LFS acts perfectly logical, there is no "modelling" of this circumstance - if a driven wheel loses traction, it will spin just like IRL.

No LSD of sorts, and you will spin the inside wheel like crazy, even in a RWD just slightly less so. I've done this even in my wimpy car without even meaning to, just doing a U-turn with medium throttle, no squealing, but up went the tach and I was actually surprized.

In my boss' old car with 250lb of torque, it was insanely easy to light up the inside tire.

So, throw setups and not feeling G forces on your carcass into the mix and LFS feels the way it does. The tires have plenty of long grip, so it is what it is.

And Centrifugal force does not exist

Quote from tristancliffe :

It is a LACK of centripetal force that causes load transfer, you to slide to the outside, and your milk to fall over whilst cornering.

Centrifugal isn't the cause.

if you want to be a smart-ass, then tell me why the LACK of centripetal force doesn't lift my wheels when bolting down a straight...

the lack of a force moves something... that's interesting, really.


the thing is, in RL the open diff is kind of self-regulating:
- weight moves towards outer rear tyre because of "cornering forces" (to avoid highly technical expressions) and acceleration
-> loss of traction or even lift of inner front tyre
-> open diff sends power to inner front tyre
-> power distribution leads to understeer
- less propulsion in general due to suboptimal power distribution (and traction)
-> less acceleration
-> weight shifts back a bit to front and inside (because of increasing corner-radius)
-> increase of traction on inner front tyre (and outer)
-> more acceleration and decrease of corner-radius
- start over

so that's basically what happens with a FWD in a corner and what I experience in RL. just in RL this is really smooth and kind of subtle (only the amount of understeer can vary a lot from one car to another).
and yes, in LFS it's basically the same, just way more extreme and it feels like the weight never gets back from the outer rear tyre and the inner front tyre is floating unless you release the throttle quite a bit. applying full throttle in a bend is more or less impossible.

if I take the XFG with one of my race setups and alter the diff from blocked to open, it handles like what I would expect of a car that has a combination of

- a suicidal high center of gravity
- tyres that have such a high level of grip that you could flip your car by just cornering it
- a whole lot of power and little engine weight
- a tiny wheelbase
- a bloody bad suspension with a lot of body roll and too hard a front

and again: if I drive an LFS-FWD the way I drive an FWD in RL, I have to fight with extreme power loss and wheelspin whereas in RL there's no spin at all.

i mean, watch the vids. if you say they're moving slower than me in LFS doing an easy lap on a cruise-server, then somebody call a doctor... when he's here we can decide whether I or you need his help... ;-))

You take a quasi-exploit locked diff setup that relies on the inner front wheel to lift to work, change it to an open diff and wonder how it doesn't behave like "a real car" (which you don't even know as I can guarantee you no real car uses a setup like that). Granted, real cars aren't nearly as stiff as the ones we have in LFS, so the bending car might counteract lifting the wheel a bit, too, but saying that LFS physics are completely from a different universe is nonsense.

Consider that in LFS the main driving feedback is visual. If you do something that increases or decreases the cornering force in such a way that would cause immediate reaction or notice in real life, you can barely even see a difference in the speed the camera rotates, if any at all.

Quote from AndroidXP :

You take a quasi-exploit locked diff setup that relies on the inner front wheel to lift to work, change it to an open diff and wonder how it doesn't behave like "a real car" (which you don't even know as I can guarantee you no real car uses a setup like that).

with bob smith's "road going" setups the effect is even worse. don't distract from the main issue - it's the same with the UF1 standard setups. believe me, the XFG setup I made to try to prove myself that LFS isn't that far off was tweaked in order to prevent wheel lifting.
I just tried blackwood, and in the first 3rd gear righthander i can "lift" the wheel when driving on the ideal racing-line with 80 kph... just floor the throttle and there you go.
as i'm not that incredibly fast in LFS I usually take this corner with maybe 110 kph... therefore I strongly believe in RL I sometimes take corners like those with about 90 kph flooring the throttle midcorner... no spin.

then I took a ride in south city, rolled slowly to a 90° lefthander, took the tightest radius possible (kind of like in real life traffic). so I turned with 30 kph, then floored midcorner. biiiiiig wheelspin and rev-limiter hitting. I then thought, ok, you wouldn't do that in 1st gear, although this setup's 1st gear goes to probably 70 kph. so I did it again in 2nd - just like turn into a crossing street. no rev-limiter hitting but still some raise in revs and wheelspin. you DEFINITELY don't get this in RL with an average car.


I mean, those of you who say it's absolutely (or at least highly) realistic - did you really compare or do you just believe in the high accuracy of LFS and search for all possible reasons why the subjective experience might differ? after all it's just another bandit-thread and he's always wrong until proven right.


for the record: just drove the FXO standard-setup with patch x30, which uses an LSD. now THIS feels much more like an open diff FWD in my universe.

... and now it's late and I spend far too much time with LFS.

Look, this isn't rocket science

Look at the G meter when you're getting wheelspin in LFS. LOOK at it.

Then think to yourself "Bandit77, with a car pulling a G or so, A) how much weight is acting on the inside tire, even including the spring, and B) how much torque am I attempting to transfer through said tire?".

If you don't get it then, then I give up. Get a Force Dynamics and feel what's happening I guess.

Why are we even arguing about what FWDs do? It's not like anybody actually drives them in LFS is it?

Quote from Bandit77 :

- a bloody bad suspension with a lot of body roll and too hard a front

Well that statment might fit with chassis flex not being modeled yet, chassis flex has a big impact. Irl they deliberately take measure to reduce its effects in race preped cars so should make a noticable difference to road car type handling when it is implemented at some future stage

Been there, done that. 2003 Chevrolet Cavalier. Spins inside wheel when WOT and turning (which is hard on CV axles BTW), has horrible suspension that makes the car roll into it, and the absolutely atrocious chassis flex doesn't help either.

If the Civic's chassis strength can be equated to a beer can, the Cavalier, in comparison, is a paper bag.

Quote from Ball Bearing Turbo :

Take the XFR out with an open diff, and report back

Any time the trans spins up in LFS, there is gearwhine.

i know but thats not what i meant
the gears inside an open diff are cut staight so everytime the diff slips youll hear it over the (lack of in case of a road car) transmission whine

Quote :

LFS acts perfectly logical, there is no "modelling" of this circumstance - if a driven wheel loses traction, it will spin just like IRL.

No LSD of sorts, and you will spin the inside wheel like crazy, even in a RWD just slightly less so.

it just occured to me that in lfs maybe the open diffs are just a tad too open too idealised

Come to think of it, my 60hp Polo is far worse than my 230hp Passat, so it might be mostly due to wimpy and poor suspension design and tires. Both have open diffs, but the Polo is soft and wobbly with a weak engine, no rollbars, whereas the Passat is low, stiff, wide grippy tires. That said, the Polo don't have the power to light up the inside front in 3rd unless I'm really trying. 1st and 2nd it does though. The passat can light up the inside front in any gear when driven hard, but I guess 380Nm to the front will do that to any tire. But the passat needs alot more torque to actually break the tire free. So bandit, maybe you have a very good suspension setup combined with not too much torque. That would describe your situation.

atledreier : my 1989 polo fancy with its 40 bhp has a front antiroll bar, sound strange yours does not have one