Chappy 2J Downforce

[JJSCHMITTY]

Hello. I was driving the toaster and I was wondering how much downforce it actually had. If you know, tell me, and if you don't, I'll do some math.

 

[roflcoptor]

" the JLO fans could create a partial vacuum which would provide a downforce on the order of 1.25-1.50 G of the car fully loaded (fuel, oil, coolant)."

From: http://en.wikipedia.org/wiki/Chaparral_2J#2J

 

[JJSCHMITTY]

What figures does that convert to on GT5's aero points system?

 

[roflcoptor]

What figures does that convert to on GT5's aero points system?

I'm not really sure what you mean by "Aero points system"... do you mean the PP (Performance Points)?

Or do you mean as if in comparison to adding a wing to a normal car and adjusting the amount of wing?

Either way, I'm not sure how to convert it.

 

[Exorcet]

What figures does that convert to on GT5's aero points system?

Only PD knows.

I saw a 2J site that claimed 1900 lbs, I think. I don't remember where the site was.

 

[Tornado]

No one really knows how much downforce it had in real life since it was rarely working well, nor does anyone know how it is calculated in GT5 (and, since PD have changed its PP level several times, they don't seem to either).

 

[JJSCHMITTY]

Well, what car going at 100 mph that has the same tire specs can turn like a 2J with the same amount of weight, with downforce? (e.g., 50/150 downforce)

 

[DGXR]

I'm not really sure what you mean by "Aero points system"... do you mean the PP (Performance Points)?

Or do you mean as if in comparison to adding a wing to a normal car and adjusting the amount of wing?

Either way, I'm not sure how to convert it.

I think the "aero points system" he's referring to is simply the numbers on the aero downforce adjustment sliders.

But to answer the question, I really don't know. That car is pretty ridiculous and a huge hot mess.

 

[Exorcet]

Well, what car going at 100 mph that has the same
tire specs can turn like a 2J with the same amount of weight, with downforce?
(e.g., 50/150 downforce)

Because you're looking at the 2J, things are complicated.

It's a fan car, so it's downforce isn't as tightly related to speed as on a wing car. A wing car will have a fixed lift coefficient (CL). The 2J's lift coefficient will be dependent on speed.

However, GT's non sense units are on our side this time (maybe) since cl can be converted to downforce easily with a few other variables. So if GT units refer to downforce directly instead of cl, we can find the 2J's
downforce in GT units (and we must remember that the GT units for other cars are valid only at one speed, and that we don't know what that speed is). I'd say that GT units probably relate to downforce rather than CL. But that is in no way certain.

So if you want to find the 2J's downforce in GT units, you'd need to take the 2J to some fast corner and record its lateral g. Then take a wing car with the same base grip (hard to figure out because the 2J is a fan car) to the same corner and find the speed at which it matches the 2J's later g exactly. You can arbitrarily set this speed as the reference speed that GT units are based on. You'll then have the 2J's downforce in GT units and be able to find the downforce for all wing cars at any speeds by multiplying the units by speed^2/reference_speed^2.

Remember that assumes GT units are downforce related and not CL related.

 

[Ealirendur]

The best bet might actually be the Red Bull versions - wasn't there a fanless variant for a regional event?

 

[Tornado]

I think that the fans can be made to be the only functioning aero on the X1 (in essence replicating the 2J), but I don't recall a fanless version of the X1.

 

[roflcoptor]

I think that the fans can be made to be the only functioning aero on the X1 (in essence replicating the 2J), but I don't recall a fanless version of the X1.

The Japanese one (X1 2010 5G) was fanless.

https://www.gtplanet.net/red-bull-5g-gran-turismo-competition-announced-in-japan/

 

[Ealirendur]

The Japanese one (X1 2010 5G) was fanless.

https://www.gtplanet.net/red-bull-5g-gran-turismo-competition-announced-in-japan/

That's the one. Unfortunately, the design incorporated larger wings, now that I look at the press release again.

Still, you could probably do something with just the X2010 by checking its max Gs at both minimum and maximum aero at two different speeds; the fan aero should fall out of the math as a constant. Extremely difficult to get accurate figures though, to say the least.

 

[mistersafeway]

I think that the fans can be made to be the only functioning aero on the X1 (in essence replicating the 2J), but I don't recall a fanless version of the X1.

The lowest the downforce can go on the X1's is 50 50, which is a shame as it could've been really helpful in calculating the 2J's downforce. It would also be interesting to see if they just have a generic "fan downforce" figure, or if they actually bothered modelling them uniquely... maybe if somebody with the correct set of skills could test the F2007 / F10, X2010 / X2011 and the 2J they could answer these questions, seeing as the game states the X1's and F1's have identical values of maximum wing downforce.

 

[JJSCHMITTY]

Does anybody here happen to know the weight-grip-turning force algorithm, and the tire sizes for the F1, X1, 2J, and a Viper? (Viper is so we can see what a car turns like with NO downforce). I need to solve this problem. I assume that PD made the X1 have a stronger fan than the 2J, and that the F1 cars have smaller tires than the 2J and the X1. This means that I need to calculate the grip algorithm at different speeds, and then put it on a graph to calculate exactly what's happening with the grip and what the car will turn like at 0/0 cambre and toe. Thank you for anybody that can contribute to this, and I hope that I am able to find the answer to this tomarrow. Seems like it will take a long time though........