Analyzing the GTAuto wing and determaning natural body downforce gains

[FastAShecK]

I believe info provided by the game and logical deduction can tell us what PD gives these cars as std or "invisible" Down Force settings. I believe this to be PD crediting some cars with natural body design down force. I've gone into it a little deep in this post, but all theories and opinion using facts provided by the game to get a better understanding. Feel free to toss in theories or opinions of your own, it's all in good spirit.

What do cars have for Down Force completely stock without the GTAuto wing installed, why do some cars have more DF inside the adjuster then others after the GTAuto wing is installed, are the impacts of the Downforce adjustments equal from car to car? These are some of the things I'm theorizing about in this thread.

I'm doing all my testing with box stock road going cars that require the GTAuto wing in order to adjust the DF. Only testing Premium Cars at the moment, 0 on the odometer & after getting an oil change. Cars tested in depth so far are the F430 series including SP1, GTR Black edition, Latest model WRX sedan, EVO X, BRZ and FR-S on top of what I've noticed casually since buying the game at release.

To start, Simply put, No GTAuto wing and you cannot see any Downforce as there is no aerodynamics tab without a wing installed. This doesn't mean there is no downforce, it just means we can't see what it is. Installing a front lip in the game does nothing to the downforce, just a cosmetic mod, regardless if in reality the DF in the front would be impacted, we have to remember its a game, a very incomplete game at that. Installing a rear wing gives us an aerodynamics tab therefore the DF is revealed, but it still doesn't show clearly what the DF was before the wing was installed, if you lower the DF settings as much as possible it does not return the pp to where it was before the wing was installed, and most often (as I haven't checked all cars) the lowest setting is never 0 in the rear with a wing, so it's safe to say the wings lowest settings are still more DF and more PP than stock. I believe we can estimate what the stock DF is with the information provided by the game.

Looking over it all, it seems to me the wing at its lowest setting adds 5 rear df points to the stock body's natural DF in the rear end's design, and the unadjustable front setting I believe is the exact amount of the natural bodies down force in the front end, and not a result of adding the wing in the rear, certainly not due to the GTAuto front lip.

The Logic I'm using

We know already cars like Ferraris get special attention in top wind tunnels and are designed to have favourable airflow over the body producing downforce. The GTR has been designed with some time tuning the body for downforce also so it's no surprise when PD credits these cars with "invisible" or natural body downforce when most cars and a few cars with stock wings are not credited with any. I would think this is because in most cases take the wing off and the trunk has no DF qualities so adding a PD wing removes the STD wing leaving no natural body downforce to account for. The same can be said for the chin spoiler. GIVEN adding a chin spoiler should impact the front DF, adding one in GT5 is purely cosmetic, but PD still credits some front DF to a few cars design using lips, etc. Cars like Ferraris are designed with lips, canard styled ducts etc for getting DF and controlled airflow over and under the car usually panelled smooth underside so that airflow goes right out no turbulence. That leaves me unsurprised to see things like 15 DF points to the front end of a Ferrari std and 20 in the rear (as my theory would suggest the natural downforce of the F430 series's to be with no wing). The same for the GTR only much less as Nissan don't share Ferraris wind tunnel body deign expertise, and simply looking at a GTR vs the F430 line it's clear the Ferraris have much better aerodynamic design. Most average cars do not get wind tunnel testing to improve DF, more to simply improve fuel economy, something increasing downforce hurts so most common cars getting 0 also doesn't surprise me remembering its a game and some things PD implemented with a cookie cutter. The Facts Adding a GTAuto wing to any car gets 15 DF points of adjusting from min to max adjustment accounting for 8PP, the wing adds between 1 & 3 PP at the lowest setting & between 9 & 11PP at the maximum setting to the no GTAuto wing PP level. I see the default slider position being 5 from max and 10 from minimum position with every car I've checked. Looking at a variation of 1.875 clicks of DF per performance point on average, but it varies with the clicks leaving basically 5 clicks ending up between 1 & 2 full PP with stock cars. If the car is modified and PP level of the vehicle increased by weight reductions, the impact of the DF slider to the PP level increases, so far I've seen it go from a variation of 8pp min to max to a variation of 10 PP min to max. Decreasing the variation to an average of 1.5PP per click of the DF slider resulting in 2 to 3 PP per 5 DF slider clicks.

In Theory

This being where I get the wing adds 5 DF points to std body DF. Each 2.5 clicks on average to get a PP point would explain the usual 1PP added with the lowest df setting, one more click down (past the -5 from lowest setting I attribute to simply installing a wing) would hit that next PP point in succession, so a gain of 1PP from std no GTAuto wing to lowest setting of 5 with GTAuto wing makes sense to me.

Setting aside cars like the Veyron that have variable DF from active wings stock. That's something I'll look into later in the thread if the topic has interest.

Comparing a few cars this becomes more and more plausible. The GTR gets 2/17 when a wing is added. Minimum setting being 2/7, remove the wing and PD crediting the std GTR body with 2/2 natural DF does not surprise me. It also makes sense then that most cars, even ones with trunk mounted wings get credited with no natural body DF, getting 0/5 as a minimum DF setting with a wing, remove the wing and 0/0 DF naturally just makes sense. This doesn't mean in reality the cars with 0/0 natural DF in the game have no natural DFin reality, chances are they probably do to some degree or another (take the EVO for example, it's front lip must have a little DF action buts gets no respect by PD lol) but this being a game 0/0 natural DF being the cookie cutter setting is again no surprise. This falls in line when looking a cars like the F430 / SP1. They are given 15/35 default setting and 15/25 as a minimum DF setting, remove the wing and the 5rear DF points that come with it and 15/20 looks plausible as its natural body DF, and in line with how it seems to me PD programmed the GTAuto wing.

This does leave open that cars with trunk spoilers theoretically have DF in the stock wing that is not revealed like this as we can't see what the setting was with the stock wing only what the body with no wing has naturally. However there are oddities with this. The Oddity This leads me to the WRX & EVO with big stock trunk spoilers. These cars IMO are slightly flawed in programming considering the impacts of the GTAuto wing. These are the only 2 cars I've seen so far get a maximum gain of 11PP, and minimum of 3PP, when all others I've seen get a min of 1 and max of 9PP. As with most cars simply adding a wing puts the lowest DF setting @ 0/5, nothing strange until you look at the PP impact. 3pp at min setting on the EVO and the WRX, when they come with some hefty wings std. That strikes me as odd. Basically PD is trying to say the initial 5 clicks of DF (the lowest setting possible with a wing) accounts for 3PP over the stock wing when on most other cars it accounts for only 1PP over often times no wing at all. Or PD is saying the stock wing is actually hurting down force lol. I can only conclude this is PD's PP programming slightly glitched. IMO the 2 cars are 2PP short in stock trim, that 2PP being added with the wing on top of the GTAuto wings std application. Hypothetically if we add that 2PP to stock PP levels removing it from the wing application, the PP oddity falls back in line with every other car I've checked and makes sense out of the overload of PP added with the GTAuto wing at the lowest setting on these 2 cars. It brings back the max PP added with a wing from 11PP to the std 9pp, and min from 3PP back to 1PP. So it makes sense of the oddity if it is a slight glitch.

More Theories

As far as the Difference in PP gain when adding a wing to a Fully modified car I can safely assume the increase in impact is due to the DF having a greater impact on a lighter car, I've not tested this, but I theories the added PP gain comes when the car has had weight reductions only. Lighten the car and an equal amount of downforce does indeed have a greater impact.

To Praiano63
Praiano63 I believe you're combining the natural DF with the added DF and attributing the PP gain from the combined amount, then commenting on what may have seemed to be an inconsistency as the amount of natural body DF if any varies from car to car. I believe it's actually rather revelling, and like Chaos Theory there is consistency in what may appear inconsistent. That inconsistency revelling the natural body DF in the cars design. Had DP gone completely cookie cutter only showing DF given by the wing we would have no way of deducing the amount of pre wing DF PD credits the cars with.

To GTP members

If this is common knowledge here, my apologies. Reading the thread I got curious and went to buy a SP1 not realizing the price of it. I had just spent a few hours farming up 2+ mill and thought nothing of it, figuring the Ferrari was in the 300 to 500$ range I paid no attention until the 1,500,000 left my wallet, holly crap that's some serious bread, and IMHO one of the ugliest Ferraris ever made, just a little bit easier to look at then an Enzo. Throw some black paint to get rid of the horrible 2 tone and blend away some of the ugliness, jet black it looks alright, but IMHO Ferraris designed by Japanese designers are an insult to the Prancing Horse, and more and more Ferrari is heading in the direction of a fleet of ugly cars Italian engineered and Japanese designed. The new California is probably the one newer Ferrari to be an exception in my eyes as its styling homage to the old school California Spider and 250GT hits me just right.

Since my curiosity cost me 1,500,000 Cr I decided to dive right into this topic, sorry if I wrote a book in the end. If you made it here lol thanks for reading.

 

[praiano63]

I need concentration to read and fully understand this long text. My english is limited.

I don't know if there is a way to check the natural DF. Perhaps taking a big square car against a low CX car , same power /torque and weight.
After this just need to check the top speed. Of course without DF parts added.

It seems also that the amount of grip for a car with no downforce parts, have something to see with the size of the tires.

I think PD consider the real tires dimension of a car to make the physic input.

 

[trackripper123]

You may want to change the title to "analysing", not "analizing". Just saying.

 

[Exorcet]

I think there might be some good ideas in here, but as it's written it is tough to read.

A few things:

The same for the GTR only much less as Nissan don't share Ferraris wind tunnel body deign expertise, and simply looking at a GTR vs the F430 line it's clear the Ferraris have much better aerodynamic design.

The GT-R is as good as the Ferrari in real life, and PD's numbers are only very, very vaguely related to real life numbers. Good example is the Viper ACR which is completely messed up aerodynamically in GT5.

As far as the Difference in PP gain when adding a wing to a Fully modified car I can safely assume the increase in impact is due to the DF having a greater impact on a lighter car, I've not tested this, but I theories the added PP gain comes when the car has had weight reductions only. Lighten the car and an equal amount of downforce does indeed have a greater impact.

This is true in real life and seems to be true in game. Road car wings are pitifully weak so it's difficult to measure things with them, but as the downforce to weight ratio goes up in race cars, so does the performance in game.

 

[TP3]

The GT-R is as good as the Ferrari in real life, and PD's numbers are only very, very vaguely related to real life numbers. Good example is the Viper ACR which is completely messed up aerodynamically in GT5.

Totally agree with you Exorcet, here is a screen grab displaying the telemetry from the Dodge Viper SRT10 ACR record run (at the time) on the Nürburgring. The downforce at 159mph is over 1200lbs.

 

[fbccars924]

OWWWWWW, My damage hurts.

 

[FastAShecK]

Apologies if the writing is not superb just writing out my thoughts lol, I'm a Gear Head, not a 5th grade English Professor lol. I think there will always be some degree of inconsistency and examples that go against the grain, or simply instances of a glitch or two, just theories and ideas coming out. I would fix the tittle but the iPad app does not let me change it, I'll do that as soon as I can.

I think the GTR IMO is close to the the F430 in performance more to the Twin Turbo 6, AWD and ALTESA. I believe the AWD GTR can put more power down, & using a Twin Turbo V6 to go against a Naturally Aspirated V8, the RWD lighter F430 needing that DF in design to aid putting power down, the heavy GTR with AWD DF in body design not being as critical. This is the same as in real life although the application in GT5 is obviously much more generic. I don't know, just theorizing. The Ferraris IMO have a higher degree of aerodynamic performance in the design then the GTR, to me it's something obvious visually, IMHO simply being close to each other in performance results does not immediately imply the DF they have must be the same, or indicate a fault in the logic I'm using. It has to be understandable that PD is not hitting numbers specific to each car as the generic implementation of 0/0 natural DF being applied to the majority of cars would suggest. To me it seems PD credits a few cars with some natural DF in the body design, but to only SOME cars, more specifically the ones with "invisible" downforce, but that's just my opinion.

I haven't looked at the viper yet, too many variables to consider without taking a look, so Ill grab a ARC when I can and scope it out. Although a telemetry grab of dynamic DF would not tell us much about the static downforce adjustments made in the game. I am not sure where your going with that point.

 

[Exorcet]

On the clarity of the post, I don't expect you to be perfect in grammar. I only mentioned it because I was having a hard time finding your point. You have a lot of information, but I don't know what conclusions you want me to draw from this info.

I think the GTR IMO is close to the the F430 in performance more to the Twin Turbo 6, AWD and ALTESA. I believe the AWD GTR can put more power down, & using a Twin Turbo V6 to go against a Naturally Aspirated V8, the RWD lighter F430 needing that DF in design to aid putting power down, the heavy GTR with AWD DF in body design not being as critical. This is the same as in real life although the application in GT5 is obviously much more generic.

The difference between the GT-R and F430 was design goals, not lack of ability on Nissan's part. The GT-R has a lower CD I think it's about .3 while the F430 is about .34 or so. They have a similar top speed even though the GT-R has slightly less power. The GT-R also produces downforce, though I'm not sure how much. The F430 does not produce a lot, only 180 lbs at 150 mph. The 458 produces 500 lbs, the ACR 1000 lbs.

Downforce also isn't just about putting power down and it would aid the GT-R as much as the F430 at high speed (the GT-R would need more downforce because it's heavier though).

The Ferraris IMO have a higher degree of aerodynamic performance in the design then the GTR, to me it's something obvious visually, IMHO simply being close to each other in performance results does not immediately imply the DF they have must be the same, or indicate a fault in the logic I'm using.

I'm not making a claim based on the looks of the cars or their lap times, but their aero coefficients (where available) and those things related to aero (top speed).

Visually, the standout difference between the two is not that one has a superior design, but that each manufacturer had different design goals.

It has to be understandable that PD is not hitting numbers specific to each car as the generic implementation of 0/0 natural DF being applied to the majority of cars would suggest. To me it seems PD credits a few cars with some natural DF in the body design, but to only SOME cars, more specifically the ones with "invisible" downforce, but that's just my opinion.

I agree, they are in no way trying to super accurately measure downforce for each car. Older race cars in particular has ridiculous downforce amounts, and are basically as well sorted aerodynamically as newer race cars in GT5.

I haven't looked at the viper yet, too many variables to consider without taking a look, so Ill grab a ARC when I can and scope it out. Although a telemetry grab of dynamic DF would not tell us much about the static downforce adjustments made in the game. I am not sure where your going with that point.

I'm not sure what you mean here That screen shot pretty much says all we need to know. The point with the Viper ACR is that it should have much more downforce than many other road cars. The 458 in GT5 has the same amount, and at speed the Viper's cornering grip doesn't improve nearly as much as the real car's. GT's modeling of lift coefficients is extremely primitive and to a degree, arbitrary.

What do you mean by dynamic dowforce and static downforce?

 

[FastAShecK]

Not really drawing any conclusion, more tossing up theories and going over the details. Mostly I'm leaning to words understanding the "invisible" downforce cars etc, but as this is only theorizing, I don't work for PD or have any inside knowledge on the programming, I'm on the outside looking in.

As I understand Drag Co efficiency, it is impacted by the downforce produced as the downforce creates drag, but it is not a direct representation of how much downforce is produced. Increasing downforce also increases drag, more downforce = more drag (This can be minimized) but more drag does NOT = more downforce. A SUV has more drag then the average car but that don’t mean its making more downforce. A box on wheels has more drag then the average car (I won’t single out any 80’s square boxes lol) but certainly doesn't mean it makes more downforce. Not saying that you said it does

Without equal testing of the downforce produced by the GTR its quite hard to say it makes close to the same downforce. 180 may not seem like much (especially when looking at 1000) however I would be surprised if the GTR makes as much.. Wind tunnel design is about minimizing drag while increasing downforce, the impact of the drag produced by downforce can be minimized and is partially why 2 cars can have the same drag co efficiency but one has more downforce than the other. With varying D/C car to car, even if really close it’s quite difficult to determine how much that D/C represents downforce.

I have great confidence that Ferrari has a greater expertise in aerodynamic performance engineering and design then Nissan. They have had more time wind tunnel testing for F1 then probably ANY other manufacture (If I'm not mistaken other F1 teams actually rent out Ferrari's wind tunnel for their own testing lol) and I do believe some of this expertise has trickled down to the road going cars they produce. The expertise they have over Nissan would represent greater downforce with less drag IMHO. I take nothing away from the GTR, I merely see it for what it is (aside from a truly great car) an AWD Twin Turbo V6 designed by Nissan. Simply making close power numbers doesn't really say what is actually hitting the tarmac. A car producing AWD 450hp is most often actually making more power than a 2WD car also with 450hp, and the 4 points to put power down can surely put more of that power down than 2 points. I also consider a lighter car is greater impacted by downforce, that downforce becomes critical as low mass makes it hard to put power down. The GTR uses its weight quite well and without it, it too would need to rely on downforce much more.

Paper numbers do not directly represent whats going on dynamically and 2 cars with equal stats getting close end result numbers have way more variables at play then simply drag co efficiency and HP. Close power and speed does not say close downforce by design or aerodynamic efficiency. My point being the F430s looks and most probably they are more aerodynamically efficient by design than the GTR producing more downforce with less drag.

Dynamic measurements are basically when you take a measurement live, for example testing a lights resistance while the light is on as opposed to simply testing the resistance of the bulb in a static state. The measurement when done dynamically are impacted by other variables, the downforce measurement for example is impacted by air density, temperature, and greatly by wind. Imagine the difference between no wind and a 50mph headwind. The headwind will greatly impact the amount of downforce measured as the air speed is greater over the wing. Even a bump in the road can impact the downforce measurement as the weight goes from positive to negative G and back.

I would really question HOW exactly was the ARC tested, was that an outside source testing or ARC doing their own testing, not saying its invalid, just when something pushes the bar like that its goes without saying its going to be under heavy scrutiny.. It reminds me of the GTR vs ZR1 battle on the Nurb, many argued about the tires used and if the tires were “prepped” at all. Independent testing always speaks louder than in house testing if yah know what I mean.


All this does indicate that PD may not be crediting STD wings with as much downforce as maybe they should, or again, is the STD wings DF not impacting PP. I was touching on this with the EVO and WRX. It would be interesting if Some in game testing showed the STD ARC wing to produce more DF than the GTAuto wing at its lowest setting even though the PP would suggest otherwise.

 

[Exorcet]

Not really drawing any conclusion, more tossing up theories and going over the details. Mostly I'm leaning to words understanding the "invisible" downforce cars etc, but as this is only theorizing, I don't work for PD or have any inside knowledge on the programming, I'm on the outside looking in.

Alright, that clears things up a little. Natural downforce as you call it has been know for a while, but I don't think there is a list detail the specs for all cars or any understanding as to why certain cars get certain values when wings are added (McLaren F1 rear wing is above average).

I think that as you said, the GT Auto wing stats are influenced by the stock downforce values chosen by PD (which I think is a shame, because it means most cars get pitiful wings and downforce).

As I understand Drag Co efficiency, it is impacted by the downforce produced as the downforce creates drag, but it is not a direct representation of how much downforce is produced.

Drag produced by lift is called induced drag. It's well understood for wings, but harder to separate from other factors on something complex like a car. For a wing it's possible to figure out lift from the drag, but you are right that it's not possible with a car.

Without equal testing of the downforce produced by the GTR its quite hard to say it makes close to the same downforce. 180 may not seem like much (especially when looking at 1000) however I would be surprised if the GTR makes as much.. Wind tunnel design is about minimizing drag while increasing downforce, the impact of the drag produced by downforce can be minimized and is partially why 2 cars can have the same drag co efficiency but one has more downforce than the other. With varying D/C car to car, even if really close it’s quite difficult to determine how much that D/C represents downforce.

I have great confidence that Ferrari has a greater expertise in aerodynamic performance engineering and design then Nissan. They have had more time wind tunnel testing for F1 then probably ANY other manufacture (If I'm not mistaken other F1 teams actually rent out Ferrari's wind tunnel for their own testing lol) and I do believe some of this expertise has trickled down to the road going cars they produce. The expertise they have over Nissan would represent greater downforce with less drag IMHO. I take nothing away from the GTR, I merely see it for what it is (aside from a truly great car) an AWD Twin Turbo V6 designed by Nissan. Simply making close power numbers doesn't really say what is actually hitting the tarmac. A car producing AWD 450hp is most often actually making more power than a 2WD car also with 450hp, and the 4 points to put power down can surely put more of that power down than 2 points. I also consider a lighter car is greater impacted by downforce, that downforce becomes critical as low mass makes it hard to put power down. The GTR uses its weight quite well and without it, it too would need to rely on downforce much more.

One thing to consider here, Ferrari, Nissan, etc, don't do all the work themselves. A third party can do the work for both, and in the modern auto industry CFD is as strong an asset as a wind tunnel. Tools like Fluent, PowerFLOW, and Star-CCM+ are pretty important to manufacturers and sometimes even more important is the support from the produces of those products. Ferrari has a lot of experience, but they're by no means untouchable, at least the F430 isn't. If there's one downforce advantage I'd give to Ferrari in the case of F430 vs GT-R it's that the former is a more expensive car. That would justify more underbody and internal flow analysis which can be expensive. However externally, I don't see why the F430 would be thought of as clearly superior to the GT-R.

On weight, low mass isn't a bad thing and it doesn't negatively impact handling. Looking at tires from a zoomed out perspective, they follow the basic friction formula. F= uN. As weight does up or down, so does traction. Connect that with F=ma and what you see is that the grip to accelerate at a given rate is always available no matter what the weight is.

Dynamic measurements are basically when you take a measurement live, for example testing a lights resistance while the light is on as opposed to simply testing the resistance of the bulb in a static state. The measurement when done dynamically are impacted by other variables, the downforce measurement for example is impacted by air density, temperature, and greatly by wind. Imagine the difference between no wind and a 50mph headwind. The headwind will greatly impact the amount of downforce measured as the air speed is greater over the wing. Even a bump in the road can impact the downforce measurement as the weight goes from positive to negative G and back.

The Viper video wasn't measuring downforce though. That would be extremely difficult. They measured speed and used a conversion to estimate the downforce. It's basically the same as a static number.

There also isn't a static measurement for aerodynamics, unless meant a wind tunnel.

All this does indicate that PD may not be crediting STD wings with as much downforce as maybe they should, or again, is the STD wings DF not impacting PP. I was touching on this with the EVO and WRX. It would be interesting if Some in game testing showed the STD ARC wing to produce more DF than the GTAuto wing at its lowest setting even though the PP would suggest otherwise.

Even if the Evo/STi wings produce downforce, the car could be lifting, so PD may not be wrong. What I'm pretty sure of is that PD does not give negative downforce values to cars, and that is by far the most common value for downforce (0 is actually not achieved by many normal cars). Older cars in particular should be terrible when it comes to downforce, but I can't detect anything wrong when driving at speed.

 

[FastAShecK]

On the point where you mistook me for saying "On weight, low mass isn't a bad thing and it doesn't negatively impact handling." I didn't say it did, what I meant was the rather heavy GT-R uses its weight quite well however remove a chunk of it and it would have to rely on aerodynamic aids to keep the same stability.

I understand your points and opinion of the F430 vs GT-R I think we may have just come to a difference of opinion on that point because as great of a Car I feel the GTR is I like the F430 better, this says much because honestly, I hate modern Ferrari's, that's just me though.

I highly question the authenticity of estimation calculations like that. I read they attribute the "1000lbs" of downforce to the combination of the front lip and rear wing. That is certainly an interesting Viper, I even read the manual gives warning of Death & going so far as the Front lip being illegal for on road use. However that claim of 1000lbs in my eyes hasn't been fully substantiated at least IMHO.

I had a little bit of free time so I went ahead and took the ARC I just bought to the Speed Test. My goal is just to test out PD’s downforce physics. What we know from reality is that an increase in downforce should show us a lower top speed. With a GTAuto wing installed I start at the lowest setting and increase it progressively gauging the impacts to the Top Speed. Everything reads out as it should, as I raise the DF the Top speed drops.

I then test out to see if possibly the STD wing has downforce not accounted for in PP, but nope, its as it should be, The GTAuto wing at its lowest setting is indeed producing more downforce then the STD wing.

I’ve not tested if the GT5 Stock specs mirror real life specifications like 0-60, top speed, etc, but I think its safe to assume they come close.

The Conclusion I’m coming to is that PD plugs each cars measured specs (HP, weight and distribution, aerodynamic profiles, etc) into the physics engine, then manipulates some variables possibly downforce, wind resistance, tire width (i.e. grip level at each corner) inside that system until the car behaves closest possible to the life counterpart. Maybe its only the cars with invisible dowforce that require this additional manipulation to the downforce in order to get the real life performance out of those cars and simply PD not coding out the manipulation.

PD is weird, whats the deal with the RX-7 Spirit R Getting adjustable downforce from the factory, and MUCH more adjustability with the GTAuto wing. What makes it so special lol