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935/78 - Let's talk setup and driving

Discussion in 'Chit Chat Room' started by Seria17hri11er, Oct 30, 2016.

  1. Well as most of us know this brute is understeery, but powerful, with a beautiful cockpit and model (KS rocks), plus visceral sounds to boot (KS ftw)!

    So I've taken my first attempts to get the beast to understeer less.


    Here is what I did.

    F ARB - down 1 click

    F Toe - 1 click out

    F Bump - 1 click down

    F Rebound - 1 click down

    R bump - 1 click up

    R Rebound - 1 click up

    Brake bias - 1 click rear



    These changes significantly transformed the car for me. Sure, it still has the overall understeer, but it was improved in the entry phase of the corner and constant cornering. Understeer was a bit worse during corner exit--but it really isn't an issue to me; I just gave it more throttle to rotate it.

    I spent about 30 minutes with this setup getting used to the car and laying down laps on Nurburgring Sprint GT.

    Time: 1:33:654

    I'm sure that can be improved.


    Obviously there is other things to be tried, which I will get to eventually. I would like to try just taking the Rear ARB up 1. Try just reducing F Bump and F Rebound, etc.


    So, what have you tried, or what do you like for the 935?

    Here is a video of the lap. Fully edited, colors changed slightly, enhanced audio levels.


     
    victor86, mantasisg 2, mESCx and 5 others like this.

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  3. Wing 0 (keeping the Gurney Flap), Rear ARB about mid-level. Gearing per track.

    Yeah, think that's it... Maybe toe, dont remember, would be closer to zero I think.
     
    Seria17hri11er likes this.
  4. Schnipp

    Schnipp Alien

    Go to Magione, Boost to 40% and just get used to how this car handles in tight turns and how to position/rotate it with applying throttle. Try default setup and tweaked once there with relative low hp.

    After you found a good setup increase turbo boost and get just to the faster speeds.


    My base setup (different values to default):
    26psi front, 27 psi rear (left-right adjustment depending on track), BB 51% (prepare for rear locking), toe 12 front, toe 18 rear, camber -0.9 rear (front camber default)

    (haven't tested ARB and suspension yet)


    But after writing the above setup in another thread I pushed the BB quite to some different settings, I use spoiler so the post doesn't get to long.

    I drove it on Spa, Monza and Barcelona today after I got the hang of the car.

    Somehow on each track it's a bit different and I've tried 48%, 51/52% and 58%.
    Barcelona I tried first, most of it with 51% and it felt pretty good, though had sometimes the locking rears. This was not really a comparison but more to check the values for the mentioned setup and try it again before I wrote the in the thread.


    Then at Spa I started with 51-52% and it was again ok, but had occasional locking rears. Just to exaggerate it a bit I used 48% and this had the effect of pretty close brake temps front and rear, slamming the brakes would lock them, but I only had a bit of trouble in one corner and with that in mind I was a bit less aggressive there.


    At Monza though the 48%, that I liked most at Spa, didn't work so well, I had quite some instability of the rear on very hard braking at T1, before Parabolica and after Curva Grande plus the fade caused a bit longer brake distance for 200-100 kph. (from 310 top speed before T1)

    With 51% I could brake harder than with 48%, a bit shorter distances, but this caused pretty sudden rear locking since the fronts fade first, then you push the brake a bit harder and the better braking rears lock.

    58% had similar brake distances to 51%, the fronts faded earlier but hardly caused rear locking, I guess this is due to the lower brake pressure to the rears.
    But what I felt that from about 120kph the brake distance seems to increase more than with the other settings.


    So in summary:
    48% gives similar fading, but hard braking locks rear easier before fading.

    51-52% gives more stability on hard braking but can tend to locking after fronts fade (added by more pedal pressure)

    58% is pretty stable, but really heats up the fronts, though not too harsh rear locking on more pedal pressure. Downside seem to be the brake performance from about 120kph.


    Brake distances were about 102-108m for the settings, only 48% got a bit worse after a few laps, might just be that rear tyre wear caused this and not brake performance/wear. 48% though seemed to be the hardest to threshold-brake after a few laps at Monza. At Spa it was more consistant.


    Conclusion:
    There isn't one good setting, it really depends on preference and the track.
     
    Seria17hri11er likes this.
  5. Kade

    Kade Hardcore Simmer

    I had to use max rear springs, max rear arb and minimum front arb to get this thing driveable around Nords. Lower the rear wing until you can't handle the faster bends.
     
    Seria17hri11er likes this.
  6. Correction on dampers. Actually it is


    F Bump - 2 click down

    F Rebound - 2 click down

    R bump - 2 click up

    R Rebound - 2 click up

    And forgot to say.

    1. 100% boost

    2. I believe 25 Degree temp on my hotlap

    3. Fast Track


    Tried that. Could barely tell any difference.


    Tried this. I was surprised it made a notable difference. Why did you raise tire pressures?

    The negative camber in the rear is gaining you rear traction and reducing understeer in the corners, but your sacrificing straight line grip during acceleration--which is very valuable to have with this much power.



    Not surprisingly, this was terrible! :D

    There was no grip in the rear at all. I drove this setup for like 40 seconds or something. It was sliding everywhere, and you couldn't put down the power aggressively on corner exit which is this car's strength. I then tried just taking front springs down 1 click, and rear up 1 click, but it still didn't feel good.

    Try my setup. You still have to use some brake to get the car to turn in with it.


    Next time I fiddle with this car's setup I will refer to this chart and try some tweaks to reduce oversteer during Phase 4 - Decreasing Steering, Increasing Throttle.

    And also will try decreasing oversteer in Phase 1 - Increasing braking - Increasing steering.

    http://www.ozebiz.com.au/racetech/theory/shocktune1.html


    The biggest thing about tuning this car I believe, is getting the load transfer right. And you do that mainly with dampers. Default dampers are very stable. It's a stable setup, as it should be.
     
    Last edited: Oct 31, 2016
    Schnipp likes this.
  7. Schnipp

    Schnipp Alien

    I use Content Manager with real weather, so atm probably often under 20°C with cloudy or overcast weathers resulting in 20°C or less track temp.

    Those were about the pressure increases necessary to get them to the optimal psi values.

    I'll give different rear cambers a go later, but -0,9° isn't excessive.
     
    Seria17hri11er likes this.
  8. Damn it! Wrong. I just rewatched my video. Boost gauge never gets in the red, so boost was default for the hotlap.
     
  9. Yea, that's wrong--does not add up :confused:. The car felt faster through the corners, but the increased rear camber wouldn't reduce understeer.
     
  10. Schnipp

    Schnipp Alien

    Correct, but Toe adjustments mean the car rotates easier into corner, but it sacrifices stability.
    Don't know if more or less would improve the setup, I just made some bigger steps and took what felt alright for a base setup from where you can fine-tune.
     
    Seria17hri11er likes this.
  11. mantasisg 2

    mantasisg 2 Alien

    Great thread, @Seria17hri11er :)

    That car setup must be tweaked, I wonder if anybody could handle it with default setup.

    I have been driving it in modern Monza and Silv67. And managed to get it driveable and did some good laptimes (for my standard haha). Also had terrible online race, because when snails backmarkers don't use any turbo it gets a bit wrong some times lol

    I don't remember exact clicks, but I remember that I have ~63front brake bias, massively stiffened front, and massively softened rear (especially rear rebound to force wheels press more towards surface, to reduce risk of rear loosing grip while braking).

    I did more changes.
     
    Seria17hri11er likes this.
  12. That is a trip. So you've tweaked it to reduce oversteer during braking and corner exit, yes? I imagine it is even more understeery, and very hard to get it to turn in! :)

    On rear rebound: You increased or decreased? Increasing will aid in reducing oversteer during braking. Decreasing is the opposite.

    And it has to be balanced with F Bump. A soft F Bump with strong R Rebound will just transfer load to the front very quickly giving oversteer. But you said you stiffened the front a lot.
     
  13. Schnipp

    Schnipp Alien

    Doesn't 63% cook the front brakes?
     
    Seria17hri11er likes this.
  14. Andy-R

    Andy-R Alien

    I've been using 56%
     
    Schnipp and Seria17hri11er like this.
  15. mantasisg 2

    mantasisg 2 Alien

    I must admit that I'm so confused now :D

    One year in AC is clearly not enough to really start understanding it. I should read some books lol

    @Schnipp @andy-riches I don't know I ran 10 lap race twice, I might have had a bit harder times at woodcote toward the end of both races, but did't felt like brakes are gone, it was getting easier to lock them up, I think. I have moved brakes more towards the front because rear was braking a lot because of engine braking, most of my setup changes were oriented to fight that behavior. I thought that if I had more brakes in the front then rear would be less likely to lock up. It is weird that you, Andy have gone to completely opposite way, and you have been owning the lap time recently, you are 1st in RSR table and I'm 21st :D Could I be wrong with my setup, I guess so :D But it did what I wanted it to do.

    @Seria17hri11er

    Yeah I have tried to eleminate oversteering wile entering as much as I could, that was pretty much my only goal - to have as much grip on the rear end as I could. Because it bites me so much in turn-in phase.

    So I decreased rear rebound to cure turn in oversteer, and it was wrong ? Damn... :D Do I understand it correctly ? If rebound is set to softer then spring extends with more force, and presses wheel towards surface with more force compensating for the lost grip during weight transfer from back to front ? It might be only in my head lol Hard to learn.

    Then stiffened front might have helped me a lot... Yes I have been balancing my rear rebound with front bump setting, I also tried to match spring rates as I have changing dampers values. My setup was pretty wild then :D I also tweaked ARBs, especially front. I have stiffened it quite a bit, because Silv67 it was written in a guide that soft front ARB is good for tight turns, and Silverstone only has fast flowing curves.

    Despite not understanding what I do, I managed to reduce PB laptime ~2.4secs.
     
    Seria17hri11er likes this.
  16. Schnipp

    Schnipp Alien

    The thing is that once the temps go beyond a certain point they start to fade, with your setup it probably happens pretty early. That's the point where it feels like it takes ages to slow down the last few kph.

    So that is the reason why I tried to get pretty much the BB pushed rearwards so temps front and rear are close and fade is minimal. But you have to be careful on downshift timing and throttle blip.
     
    mantasisg 2 likes this.
  17. mantasisg 2

    mantasisg 2 Alien

    No way I'll ever be good with downshift and blip timing. I just didn't born with that skill, I doubt it is possible to learn :D
     
  18. I think if you are having a problem with oversteer during braking, you're probably not blipping the throttle enough. This car needs a huge blip of the throttle. You really gotta get the RPMs up.

    Anyway, whenever you are thinking about/tuning dampers you gotta think about one particular cornering phase at a time.

    CORNERING PHASE DEFINITIONS

    PHASE 1: Increasing braking + increasing steering

    PHASE 2: Decreasing braking + increasing steering

    PHASE 3A: Increasing steering at constant throttle

    PHASE 3B: Decreasing steering at constant throttle

    PHASE 4: Decreasing steering + increasing throttle (or decreasing braking)
    Ok, so maybe you are experiencing oversteer in Phase 1. What you need to do is think about in what mode the dampers are working in during that phase.

    So in Phase 1, your Fronts are in Bump, and your Rears are in Rebound.

    So, if you increase F Bump, you are stiffening the damper, and accelerating load transfer to the front tires, but reducing chassis and body from pitching forward as much--and therefore reducing the amount the rear end is rising up.

    Do the opposite and lower F Bump, and you soften the damper, make load transfer a little slower, but chassis and body pitch forward a bit more--and the rear rises a bit more.


    Essentially what you did by increasing F Bump, was help to keep the rear wheels planted during braking--reducing oversteer.

    Bear in mind, you can also help to keep the rears planted by increasing R Rebound. Increasing it allows the Rear Dampers to extend faster--again helping to keep the rear tires planted.

    But, you did the opposite, and decreased them, making them extend slower.


    But, pretty please, bookmark this and refer to it when tuning dampers in the future! Just reference the chart! It's really easy to follow the chart!

    http://www.ozebiz.com.au/racetech/theory/shocktune1.html
     
    mantasisg 2 and Schnipp like this.
  19. Andy-R

    Andy-R Alien

    Thx bud! I did change a few other things but im not really good with setup, im sure aliens will destroy that time ;)
     
  20. mantasisg 2

    mantasisg 2 Alien

    Thanks @Seria17hri11er , it is really getting clearier for me now :)

    Still a bit confusing, especially because I though that rebound is working a way around, basically mistaken - to +. Gotta go and try get Moby Dick under 1'26 at Silverstone.

    Well... after I'm happy with lod B of XJ13 hahaha

    By the way 935/78 bites ether on phase 1 or phase 2. I used to spin in phase 1 a lot at modern monza while braking towards T1, and phase 2 at silverstone at any crve lol
     
    Seria17hri11er likes this.
  21. Schnipp

    Schnipp Alien

    I think the car is relatively easy to catch and/or hold a slide if the rear steps out. Of course it stands in the way of fast times anyway if oversteer happens.
     
    Seria17hri11er likes this.

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