ACC ACC fun Run Monday's

Discussion in 'ACLOZ Past Seasons' started by marty, Jun 25, 2019.

  1. marty

    marty AC Server Legend

    Posts:
    1,631
    Likes:
    2,417
    Dont be too quick at the change of sessions, it seems it takes a second or 2 for the weather to actually figure itself out. ;)
    andyo450, Wally and Rolz like this.
  2. SteveDrivingSlowly

    SteveDrivingSlowly ACC Results Ste(ve)ward

    Posts:
    832
    Likes:
    1,333
    I remembered another thing from Aris blog post about the Porsche cup car that may explain the late race strangeness in combination with the temp and weather changes - as the fuel amount in this car changes, the handling changes A LOT. The engine is in the back but the fuel tank is actually quite far forward - meaning that as the fuel load lightens, the front of the car raises up and not only reduces the weight on the front wheels but also changes the angle of attack and therefore aerodynamics of the car. What I was feeling in the faster corners in the last twenty minutes was a lightening of the rear - which is maybe due to the reduced angle of attack (raised front end?!?) leading to less downforce on the rear.

    I had also dropped my car all the way down as far as I could without changing the aero balance - so possibly magnified the effect for me. I was also a lot slower in qualy than I expected to be, with the car feeling very nervous on only 14L (although hard to tell in the rain tbh).

    That will teach me for not running whole stints in the car during practice - I set it up with a full tank so it felt decent and just went with that.
    tezpez85 likes this.
  3. tezpez85

    tezpez85 Professional Gold Member

    Posts:
    447
    Likes:
    694
    Right, so the front needs to be setup a bit lower on a full load to combat fuel burn-off late race I guess. Wouldn't happen to have a link to that post would you?
  4. SteveDrivingSlowly

    SteveDrivingSlowly ACC Results Ste(ve)ward

    Posts:
    832
    Likes:
    1,333
    Here you go mate: https://www.racedepartment.com/threads/assetto-corsa-competizione-the-porsche-911-gt3-r-blog.170083/

    And yeah, that was my thought - raise the rear/lower the front so it's very aggressive rake at the start of the race (probably more stable/understeery) and balanced just right at the end as the front lifts up. Assuming no other ill effects!

    I'm gonna keep popping this in every now and again..but this car is worthy of it's own league I reckon!
  5. mesafto

    mesafto Rookie

    Posts:
    153
    Likes:
    130
    Agressive rake (low front, higher rear) would make the car more ballanced to oversteer i thought, but with fuel burn will bring the ballance back to neutral.
    Isnt that right?
    jasondull1986 likes this.
  6. jasondull1986

    jasondull1986 Professional

    Posts:
    882
    Likes:
    668
    PSN ID
    jasond1986
    Good to have some good racing last night had a couple of great scraps where it really highlighted what an awesome car the Porsche is.
    andyo450 and SteveDrivingSlowly like this.
  7. SteveDrivingSlowly

    SteveDrivingSlowly ACC Results Ste(ve)ward

    Posts:
    832
    Likes:
    1,333
    I thought more rake = higher wing angle = more downforce at rear, more grip at rear. Of course within the boundaries of effective aero (not stalled, not moving on the springs so much it loses efficiency). I could be wrong...?
  8. KoAStR

    KoAStR Like a bowss Team Raceonoz Gold Member Super ROOZ

    Posts:
    7,700
    Likes:
    3,735
    PSN ID
    KoAStR
    I think both theories may be valid depending on cornering speeds and rate of direction change:
    For large/sharp changes in steering angle i.e. slower tighter corners, more rake = more oversteer due to suspension roll-centre kinematics
    For small/smooth changes in steering angle i.e. fast sweeping corners, more rake = increased aero, where effect is dependent on aero design but for this car makes sense effect is stronger at the rear (observable in the setup menu % aero bias).

    I would be concerned that lowering the front alone with a high fuel load has a compounding effect to increase snap oversteer tendancy. So to mitigate this what about if instead (or as well?) you increased the spring rate so that the fuel load has less effect of the ride height (and therefore rake) of the car. This may be mean the rake and aero stays a bit more consistent throughout the race.

    Also when changing ride height all round take care to observe the % aero bias in the setup menu. Steve if you just lowered the car evenly it's likely you changed the aero bias which may have also contributed to unbalancing your tune. Try lowering it it assymetrically to maintain constant bias. [edit reread your post and you already did that :thumbsup:]
    Last edited: Aug 13, 2019
  9. SteveDrivingSlowly

    SteveDrivingSlowly ACC Results Ste(ve)ward

    Posts:
    832
    Likes:
    1,333
    Thanks mate good tips and the spring rate change makes a lot of sense!

    When I lowered the car, I kept the balance the same as it was originally - so the front dropped to zero but the rear stayed up a fair bit, and I used one click more rear wing angle to fine tune to the same exact value. This made for a very smooth drive on a full tank...will definitely try cranking the front springs a bit to see if that helps to stabilise the front when fuel load is lessened. Cheers mate!
    tezpez85, andyo450 and KoAStR like this.
  10. andyo450

    andyo450 Team Driver Super ROOZ

    Posts:
    156
    Likes:
    349
    That guide you linked is for the 911 GT3-R not the 911 GT3 Cup. Most of the stuff is applicable to the cup car but it relies far less on aero than the GT3 spec counterpart. The springs are also locked in the cup car so that's out for ride control. Its a good tip for the gt3 though.
    Most of the shift in balance late race would be down to the change in weight distribution. We burnt ~63 Kgs of fuel over that race which is around 5% of the total weight of the car I think. Even if that only equates to a 2% shift rearward in weight bias its a HUGE change. Also worn tyres and a lower grip surface at the end would've exacerbated the balance issues.

    Koastr's right about rake. Its effects vary depending on a lot of factors. Namely speed, whether or not the car has a diffuser and suspension design (I don't understand this one much).
    For low speed rake is used to rotate the car, it also reduces traction a little bit.
    In high speed its used to maximise aero performance of the diffuser (the cup car doesn't have one) and to a far lesser extent the rear wing. It still has the same effects on the mechanical balance of the car as low speed but the rear usually compresses more than the front at high speed and aero masks it to a large degree so its far less obvious here.

    Rake's a very complex concept that even F1 teams don't agree on so I doubt we've got much hope of figuring it out completely
  11. SteveDrivingSlowly

    SteveDrivingSlowly ACC Results Ste(ve)ward

    Posts:
    832
    Likes:
    1,333
    That's why you are at the front and I'm way back...you're paying attention!

    Are there other ways we can stiffen up the suspension on the cup car and try to reduce the shift in balance?
    andyo450 likes this.
  12. Captain Barracuda

    Captain Barracuda Rookie

    Posts:
    153
    Likes:
    181
    +1 to pretty much all of this. I wouldn't be using rake to increase downforce with the cup car due to next to no diffuser, if it helps you point the nose in the right direction in slow corners then go for it, but there could be negatives through faster corners as the minimal downforce gains will be outweighed but high COG at the rear where the weight is. Perhaps rear brake bias and a bit of trail braking can achieve the desired result here.

    Regarding how suspension is effected by rake - it directly affects your caster setting so be mindful of that.

    I also found no benefit to running the car super low. It just affected stability over curbs and bumbs. Did some testing with the car prerace, dropping it on it's backside was one of hte things I tried and i went back to ~98mm rear ride height. Got my hands on Rolz' and Marty's setups and they were also running in this area. Low isn't always the best option.
    Last edited: Aug 13, 2019
    andyo450 and KoAStR like this.
  13. Captain Barracuda

    Captain Barracuda Rookie

    Posts:
    153
    Likes:
    181
    Shock settings to an extent. As the springs remain the same though 'stiffness' won't change much. You could max out the bumps but then this won't allow the shocks to do their intended job properly. Stiffening the bars can have the effect of stiffening the springs a bit, but again they're serving a different purpose. You could work on the bump stop rates but this will only affect you when you've blown through your suspension travel.
    Wally and andyo450 like this.
  14. andyo450

    andyo450 Team Driver Super ROOZ

    Posts:
    156
    Likes:
    349
    Like Barracuda said not really. Brake bias is probably the most powerful tool you have for this in the cup car. Going forward even just by .4% or .6% when you feel it start to get sketchy should help a little bit.

    The best way I found was changing the way I entered corners slightly. By braking a tiny bit earlier and carrying a little bit less entry speed you're not putting the stress on the rear of the car. I found using more steering lock on entry to scrub the fronts (obviously this will wear the fronts out quicker than usual so probably not a good idea on long stints) for the high speed stuff surprisingly effective too. Then when you're getting ready to exit unwind the steering a touch so the front regrips and give it a jab of throttle should help with exit understeer. That last bit does have the potential to go horribly wrong though... :cautious:
  15. SteveDrivingSlowly

    SteveDrivingSlowly ACC Results Ste(ve)ward

    Posts:
    832
    Likes:
    1,333
    Makes sense gents - thanks for the explanations, I’ll definitely be trying some of this out.
  16. Captain Barracuda

    Captain Barracuda Rookie

    Posts:
    153
    Likes:
    181
    Off topic, but I've just noticed Kunos have added 2 official servers in Asia. Pings are better than Europe and US (~170 for me in Melbourne). Might be worth trying to join these casually above some other servers so they see them getting used. It could help us getting a CP server at some stage.
    krunch and SteveDrivingSlowly like this.
  17. marty

    marty AC Server Legend

    Posts:
    1,631
    Likes:
    2,417
    170 is what we can get in west coast US, that would be similar to Japan I guess. Are the servers restricted? Are they actually Kunos official as anyone can call a server that if they like. Did they mention adding servers in Asia in the forum but at the same ping as US can get it seems a bit useless for us.
    SteveDrivingSlowly likes this.
  18. Captain Barracuda

    Captain Barracuda Rookie

    Posts:
    153
    Likes:
    181
    Yeah it is equivalent to west coast USA, Kunos USA servers are central USA and looking at the listing right now the US servers are 230 ping, and the asian ones are 160-170. There are 2 Asian ones, both with 3 track medals and 50sa restrictions. Assume the're legit Kunos servers.

    Edit, I've asked the question, will confirm legit once I hear back
    SteveDrivingSlowly likes this.
  19. SteveDrivingSlowly

    SteveDrivingSlowly ACC Results Ste(ve)ward

    Posts:
    832
    Likes:
    1,333
    This is awesome, I will get on there for sure
  20. Captain Barracuda

    Captain Barracuda Rookie

    Posts:
    153
    Likes:
    181
    Ok confirmed by Minolin that they are not his servers, false alarm