Hi community, I've been working on aerodynamics of my car and I've searched a lot and I didn't find anything about. My problem is about some parameters, talking about FRONTWING, REARWING or BODYAERO. I don't undesrtand FWUp/Down and FWLeft/Right, I think the car never will move up or down, or I don't get it. If someone can explain how it works, which forces I have to put there? In the other hand, the DIFFUSER I don't undesrtand what there is in the physics guide about DiffuserLimits and DiffuserStall. Can someone explain the parameters that it takes and how exactly works? Thanks for your time.
Hello, Are you talking about this guide ?http://meetme.bplaced.net/rF2_onlineTools/ISI/PhysicsGlossary.htm Understanding aero is very important to correctly model every car, even not aerodynamicly focused ones, I am working on that too. I am not the one who could tell things straight, I am only supposing and searching ways to figure out stuff as well. I think the up/down values are for when the car body moves in those directions, thats exactly what you think too. Car body does accelerate upwards and downwards in various situations, most of them probably has little significance, but some are more significant such as cars being bounced off by the curbs or by some other rough terrain features, going over jumps and getting some air, in accidents when car body migh move in all sorts of ways... I was thinking recently to experiment with aero up/down values for Y direction to attempt providing some more cushion for cars when they land down from getting launched upwards a bit by harsh kerbs, sometimes they look like they fall down too fast... The left/right values should be pretty much literally the same thing - changes in aero. Just for the accelerations to the left or to the right.... It seems to be often the case that for up/down values there is only Y axis component, and for left/right there is only X axis component, or they are at least majorly dominating. Also they seem to be almost certainly always the resisting force, kind of drag for that motion. So if the body part moves to the left, the force appears that is directed to the right side. I think if you'd make this resisting value very high you could create an understeer effect for the car. I think the up/down value is quite interesting to play with for how the car would interact with various kinds of situations when cars get airborne in some particular way, for example make the car that resists little for upwards motion, but then has very slow and soft landing I don't have any diffuser experience. But I know that proper diffuser is very rideheight sensitive, so proper stalling simulation of it is big deal for cars that use proper diffuser desings. I could possibly be wrong about anything that I have said here.
One way to begin to learn how different sections of the aero package afffect a car, is to make outlandish changes well beyond the normal scope of things. The results will be so exagerated that at least you will see what the changes do. Then you could begin scaling the numbers back to the more precise values.
The following is from Bristow's bible for the rF1 HDV file. Things may be slightly different in rF2, as noted in the Physics Blog, however it should give you a good idea of the fundamentals.
Similarly, Yoss wrote helpful info for rF1 which covers aero. It is available at http://yoss.free.fr/rfactornfr/Modding_Tutorial_Website/PhysicsGlossary.shtml#HDV
@mantasisg This might just be a language thing, but avoid "acceleration" in terms of aero directional forces. It's all about speed (velocity). @alb.sg a car sliding completely sideways will have drag and lift (positive or negative). Without those parameters this would be missing, as the 'standard' aero settings are all about moving forward. You define it down to each part which can help emulate some handling-focused aero tuning. That's the basic concept - the above links cover all the details.
For stall the most important are DiffusserLimits var1 and DifusserStall var2. DiffuserLimits 1 sets height reference to begin stall. It will happen when height is lower than DiffuserLimits 1. DiffusserStall 2 sets the amount of downforce lost. The more positive is the value, the more you lose. About DiffuserLimits 2 and 3 , diffusser downforce will not change when rear ride height or rake are higher than these numbers. Here i play a bit with those parameters, not sure whether it is really revealing, though...
I tried some wild changes with those FWup / RWup / BODYup parameters and also tried removing them - but I can't detect any change to the vehicle - can anyone confirm those parameters actually do something?
"Up" means when the car moves upwards. Think of a helicopter taking off. The only time you'll get significant velocity, and therefore forces, in that direction is if you're somersaulting.
Makes sense I guess. The issue I'm having is the car taking off, particularly the front, at that infamous Nordschleife crest. I have the real world F/R aero loads (plus other relevant real world data - weight distribution, tyre/suspension spring rates etc.) and whilst there is a little (a few N) lift at the front and a bit of DF at the rear of the car, the real car definitely doesn't do that on that crest, so I wondered if there was something not right in these values that might explain it.
It won't be the up/down ones. I suspect you're thinking of effect rather than the incoming air direction that up/down refers to. Often with a front wing the issues arise from the third lift parameter, and too high a FWHeight setting - because if you don't limit that calculation it can skyrocket. Try very basic FWLift values first, like 0 for the 3rd, and even 2nd, values. If that helps then redo the other figures and graph the results to verify there's no issue.
I was kind of, yes - thinking that as the front starts to lift then the air starts coming from under the car rather than purely from in front, not much, but I wasn't sure if the UP/DOWN starts to come into play at all here, or even over bumps (as the car moves vertically as well as forward). I had set the 2nd and 3rd values to zero already actually to try to narrow down the cause. You mention FWHeight - this one I assume: FWMaxHeight=(0.3) // maximum height to take account of for downforce I'm struggling to visualise what this line does (I notice there isn't a RW equivalent) edit: I'll answer my own Q with this from Yoss.free.fr: FWMaxHeight= From this height onward the front wing will not lose more downforce from an increase in ride height. With a high value the car can flip when the car leaves the car jumps, value should be around 0.2 for race cars.
Yep, that sums it up. The rear wing isn't height sensitive, hence it doesn't have that parameter. The aero effect of bumps etc is negligible, because when you think you might be going 50m/s forward and your wing might be doing 0.5m/s vertically (momentarily) that's still massively in favour of the forward motion, and aero effects. I was away from my PC so trying to reference things from memory - the parameter I was trying to refer to in regards to height is FWLiftHeightPlus. That's the one that allows you to give some extra downforce as the front wing gets close to the ground, but when you do that it can create lift when the wing raises up. You can cut off that progression and lock in your 'maximum height' using the FWMaxHeight. It's best to graph lift vs height using those values, and check where the cutoff should realistically be.
