Hi all, I admit I'm really bad at understanding the finer workings of a diff, but just did some readup and can't get my head around what happens in game. In default setup my Lotus F1 car has Pump 20% Power 8% Cost 15% Preload 35NM And I really suffered from spin out of corner (even a bit on straight). Since all the other oversteer/understeer balance (turn in, mid corner) was excellent I didn't want to fiddle with the suspension and would actually have prefered a different "engine map" (lower torque at lower RPM) but since we can't do that I played around with the diff. What I ended up with was: Pump 10% Power 5% Cost 10% Preload 25NM Now after some post-race reading on how these settings work in game, actually what I permitted is more wheel spin (i.e. a higher wheelspeed difference) because Pump and Preload both have been reduced. Yet it cured the problem with the acceleration oversteer/spin out, the car does no longer bite my head off. Does this make any sense to anyone? I'd really love to understand for the future what goes on here. Looked trough a few available setup guides but they don't usually go into such fine detail.
I'm still not exactly sure what the pump is but the outcome makes sense for the other settings. Power lock. The more power lock, the more the 2 wheels will try to spin at the same speed under power which can have different effect dependant on how much you're pushing the car. I'll explain it in extreme cases just to make it clear. Image a 100% power lock where both wheels spin at the same speed. This will initially create a ton of understeer because both wheels want to turn at the same speed so turning the car is very difficult at that point. In a (for instance) left hand corner the inside wheel has to do less distance than the outside wheel, so understeer. This is offcourse up untill the point where you start using the slip angle of the tire at which point the car will most likely snap sideways but usually in a pretty controllable manner, hence why driftcars weld their differentials together. Now imagine a power lock of 0%, both wheels spin independent from eachother and the torque goes to the wheel with the least resistance. This will initially give the feeling of a car that can easily rotate (without any slip angle on the tires) because both wheels aren't working against eachother but the difference here is when you start to spin your rear wheels, it will just be the inside unloaded wheel which isn't the biggest factor of the available rear grip at that moment. This will give a more stable car but it will usually cost you in acceleration because you spin alot of power away on the inside wheel. The downside of such an open configuration is that that the car can suddenly snap very violently on you when the inside wheel spinning away suddenly has just enough grip. Preload is essentially adding more lock on both the power and coast side, so a higher preload means overall more locking. I have to say tho, I have noticed that sometimes the setup screen is setup the wrong way around where a higher percentage is actually less locking instead of more locking but that's quite easy to test. On the coast side, put it on 0 and try to trailbrake in a quick corner and then do the same with the maximum amount of locking and see which has more oversteer. The more oversteer, the less locking. For the powerside it's a bit more difficult to immedeatly notice since you usually cant go for either 0 or 100 so the trick of just trying to do a burnout and see wether both wheels are leaving black marks isn't always evident but telemetry can always help here. So the trick, like with every thing in a car setup, is find a compromis between driveability out of a corner and not losing all the power to the unloaded wheel.
OT Forget ramp angles and clutches, they do not work in GPL as real life. Not to mention GPL and rF2 are completely different animals. None the less there is some good stuff in here. http://web.archive.org/web/20081220015710/http://geocities.com/n_heusink/setupguide/guide.htm
Thanks for the details Timpie, and Durge thanks for the guide. It pretty much says the same as Timpie already figured out... see quote below... Timpie, the "Pump" is the total Diff characteristic (0 = Open, 100 = Welded). Power and Coast are then sub-refinements, and Preload is a threshold. So basically now the summary as I understand it: If the Diff is "welded" then both rear tires spin out at the same time, if the Diff is "open" then the unloaded tire spins much earlier, the loaded tire gets a smaller share of engine power (and thus keeps traction, but at reduced acceleration). I guess my aim is to find the setting with some manageable oversteer (slow onset of both wheels spinning). I love it how physics/mechanics come to life in this sim. BTW, the article also might explain why with some power on while braking I had crazy understeer.
