Differential Tuning Discussion

The extreme diff settings (clutched) help very slightly but the symptoms are still there. Like I mentioned in another thread, when you try to go negative (!) preload like -20, you suddenly turn in so easily, even too much, it will almost rotate around its own axis.

The problem is, that would NEVER be done on a car like this.

I noticed on F1 classics that this is still there but not as pronounced, you only really notice it on tighter hairpins.

Other "normal" cars dont have this issue per se but I believe the clutched LSD tuning still doesnt do as much as it should.

 

I agree also with you guys and Cr,Damian, ect at the end of the day this has to be a fundamental issue.I tried spool for a comparison and took off a second in the Brab that does not makes sense to me (it was not hard to do ) aside from anthying else I find strange.

I think between all the input so far and knowledge on the subject (yourselves, crim, damian, ethan driver experience, videos of the cars in the day a few others).

A comprehensive Bug report to summarise perceived faults may help us all. They are more believable than they were but? still remains.

Ha If I could get Ethan the driver to try ams2 in in a rig he could give absolute correct comparison, though he has as he said tried sims I dont think he has it or the time.
I cant think of another driver to contact atm, but wont give up looking. There is somebody I had in mind but they only race modern.

 

I love these things (retros etc) , I spent most of the last 4 weeks or more in the Brabham getting to know the car, Its still up there at the top of the list of Fav cars. But here we are 6 weeks or so and many thread pages and there still seems to be a
Fundamental.
It is as you say 0&1s which to quote Ethan

Just my opinion of course but
I love the new v10 but it has little character like most modern compared to the old stuff, you drive it its fast its very grippy as it should be, not tricky, its great. tremendous fun. but not a preference for me. I would not like to see what we have "put on the back foot" by the great new content
Yes I think its driveable (Brabham) even in default (my tt shows that and its fun) will the cars progress I believe so.
But

When comparing a sim to a real car experience I hold it in high value, and have to take into account, hence. From Ethan just a few of the exctracts.

s
Seems difficult to achieve here

Questionable here

For me anyway its very effective

The cars seem overly restrictive here it seems
hence various posts
Added to whats been tried by the guys on these relevant threads and discussed here and on other threads. The accuracy of what we have seems to be lowered by a possible fundamental problem.
All in good possible taste.

 

I did find in my research that occasionally ramp angles are backwards depending on the differential manufacturer's reference plane. I considered for a moment that perhaps we had it backwards, but just as a sanity check, I went in and even though it will not allow you to open it up to 90 degrees (I dont really understand that, myself, 89 degrees is the limit currently. It's probably some sort of divide by zero type error, though.), it wont let you go less than 25 degrees. The 25 degree minimum makes perfect sense if you consider the shape of the windows the ramps create. You make the ramp angle too steep and the window will simply be too small to fit the spider pinion cross shaft posts into them.

Has anyone played around with PC2 to see how this behaves in that?

My first exposure to ramp angles was Grand Prix Legends, so you can try this stuff in other games and see how it works in those as well.

I just checked for some context from the PC2 world, and found this:
Episode 18: Differentials - Project CARS 2

There are some nice guidelines in there about how they should affect car behavior as well. Its interesting they mention 90 degree ramp angles to "Disable" that side of the LSD, and yet we do not have that option. It's curious...

I have also seen people say that the preload seems unusually dominant in diff behavior elsewhere on the boards, so that may have something to do with it. A high preload in practice, despite a low nominal preload, would probably cause behavior like what we are seeing.

I also caught this on that page:

From this I propose that the cars' handling with the geared diff is likely much closer to what is intended than with the period correct type of differential used. Again this is specifically addressing the behavior of the Formula Retro.

I have said this before perhaps, but I think this may have a lot to do with how large the rear tires are for the F-Retro... with giant rear tires and relatively little downforce, they may have more mechanical grip than most other cars in the game, which would make any odd behavior with the diff tuning far more obvious than with other cars. It could be that even mild amounts of anti slip in the diff have an over-size amount of influence in the car handling due to the SETA tire model. These are large, very wide, grippy racing slicks on cars that have a relatively subtle amount of aero grip and are fairly short wheelbase and very wide-tracked. Add in being lightweight with fairly powerful engines, and this is a perfect recipe for being extremely sensitive to differential settings.

 

Not me at least not yet

Agree curious Mm

Yes maybe, I recall Ethan talked of the tyres and the extreme effects on them. May well have more bearing on issues relationship: tyre to Transmission & vice versa ? delicate relationship
Quote
The large diameter sidewall bias ply tires can get into a condition where when you are asking the tire to slide sideways and forward with wheelspin at the same time. So the carcass of the tire doesn’t know what to do and it loads and unloads in both directions rapidly causing a high frequency vibration. It is easily heard from outside the car and it sounds like hitting a serrated kerb or something of the sort, sortof a buzzing sound. From the driver's seat, it shakes your body quite badly, blurs your vision, and will knock the air from your lungs if you are not prepared. (You breathe out before going to power and hold your breath out until the shaking stops). All the big power cars do this when you get to the limit, but the Brabham with its short wheelbase is particularly susceptible to issues relating to tire shake.

Might be just me but I find they have a lack of overall mechanical grip slow or fast esp front

The complexities with software/data, models etc etc and lack of data from these types of old vehicles just make the job of accuracy more difficult, It would be nice to interview an old race engineer from the day! there are other historic drivers out there uk and across the pond, who knows.
Devs have ongoing development with ams 2 as we all know and updates come fast and thick credit to them. Meantime encouragement to drive them must be maintained imo rather than discouragement! Info and research from yourself and the others keeps pushing in the right direction. I know research takes time. and its passion that helps.

 

PRELOAD
from your link.
This controls the amount of built-in lock applied to the differential clutches before any Power or Coast effects are added. As such, it will affect the balance of the car when cornering in a neutral throttle situation and will also affect the smoothness of the transition going from off-throttle to on-throttle.
ref 3 states. Power: self explainitary torque applies
Coast: almost zero forces Neutral as in quote
Overrun: off throttle and engine braking torque applies
Call me old fashioned but in the world we live in the terms used ie Coast used instead of " off throttle" or "overrun" dont make things clearer to a non mechanical mind
When setting up backlash or diagnosing diff bearing/ Crownwheel / pinion noise in power , coast, overrun conditions
3 states were in my day always considered
I think the Brab has a very strange behavior when
the transition going from off-throttle to on-throttle. It too me feels like theres a lag or delay in reaction here
Nice to see it referred to in quote. imo old opinion
Some would see coast a putting in neutral going down hill which it would be

 

Yeah the true "coast" state would be transmission in neutral, not off throttle. You have to have no engine braking, regular braking, or acceleration happening for only the preload to be playing a role in behavior. I think in practice this is just a very unusual condition for a racecar so it's not really talked about much. You're almost always doing something that's loading the differential.

Think of "Coast" side as the engine-braking side, regular braking, I believe, has the same effect , while true coast with zero load on the pinion gears would be probably slightly downhill, in neutral, with no braking happening. The issue is that this is a transient state between power and coast states, so you pass through and it plays a role in car behavior, but it's almost never a static condition.

 

Yep nail on head. I only posted it because if frustrates me and its can be misleading. just takes me back to college days lol Fundamentals of Motor vehicle Technology text books ha, blimey time flies! (all nvq's these days)?
The unloaded state in the Brabham as mentioned seems to me to have an overly long period before the engine breaking takes effect increasing or decreasing preload make a difference but it still "lags" from what I would expect from a real world transmission.
Almost time to fire up pc

 

Hi everyone.

I read the discussion, tried out the cars...What do you think about the idea of this hyper effective LSD's being a result of some issues with tire contact patch and grip/load calculations?

This hypothesis bases on experience with karts: it is definitely possible to notice [simulated] kart's rear inner wheel lifting a bit when turning the wheel due to front suspension geometry as it is in real life. Despite this, it is never possible to induce oversteer on corner entry off throttle as if the inner tire had never lifted. Only when throttle is applied rear axle grip changes noticeably. This seems to be an extreme example of issues being discussed in this thread, just as kart's solid rear axle is an extreme example of LSD. I'm almost sure this does not match with almost everyone's experience with [mainly oversteery] karts IRL.

 

For me I have little cart track time here or irl (long time ago once) so cant compare, but interesting that you bring it up. Something is not quite correct or at least off. Others have tried allsorts inc.

Since Irl negative preload does not exists according to our consultant Driver then diff and, or, plus, diff /tyre relationship has to be considered. The fact the settings allow this is wrong, Devs are taking note and the settings may be curtailed I should think.

Since the last updates I have not really made comparison runs, more updates today, (not tried yet here) so maybe I will try later with the most familiar combo to me.
I will run some online test races regardless, tonight just for the fun of it. Plus its cooler here uk lol

New content is great to explore and enjoy as I have done, and its then too easy to not go back and enjoy any improvements on previous cars.