# Endurance Oreca 07 lift to drag ratio

Discussion in 'General Discussion' started by avenger82, Jun 19, 2018.

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1. ### ComanteRegistered

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Unless point of application of aerodinamic forces is perfectly above the tire, there will always be discrepancies , as you must take into account that offsets in vectors induce a rotation, throwing the wing load in another direction, vectorial sum is then different from arithmethic sum.

2. ### Stefan_L_01Registered

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I hope rf2 include everything in the telemetry, else its useless. Being off to axle would change distribution on tires but not the sum. There must be an equilibrium of forces.
I would expect tireload to be vertical down on road which means perpendicular to movement on a straight road. Same for downforce. But it isnt and why similar cars show different number "characteristics" is one more rf2 mystery

3. ### LazzaRegistered

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@Stefan_L_01 If reported total downforce and total tyre loads aren't matching, then something is obviously being missed. I'm just making two suggestions on what that could be.

I think you're overlooking the effect of leverage. A wing out in front of the front axle will produce more front tyre load than the downforce it produces directly, because it gains a mechanical advantage (so to speak). Only if the front and rear downforce are equally offset will there be a balance. The proper way to measure aerodynamic influence on the tyres is to measure the change in tyre load. In real life that's the only way, because you can't take (most) aero components off the car and reliably measure their downforce; you need them on the car to measure what they do on the car.

So I wouldn't rely too much on what the front and rear downforce figures say. Your own findings confirm that.

4. ### Stefan_L_01Registered

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No you are wrong as leverage will shift load from tire to other tire, but the sum of all tire loads remain the same

5. ### avenger82Registered

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If you have legitimate concerns maybe directly ask developers? If it's something they would look at and turns out to be real issue, then it should be fixed.

Edit: It’s not Forza or GT Sport where users don’t care much about physics.

Last edited: Jul 4, 2018
6. ### mclarenf1papaRegistered

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As seems to be the usual in this thread, there's a lot of talk without a lot of progress...so I did some tests.

"Car weight" is just tire load minus downforce. I didn't check if the downforce loads were at the wheels or not (though they probably are) since it wasn't relevant for this test. Only looked at total loads, not distribution.

Undulations in the track make any difference essentially indistinguishable. I checked this manually just to make sure...while there's not enough precision to rule out a <50 N difference, I can definitively say that at least for the Oreca, the 150N-500N discrepancies that Stefan suggests exist for other cars are not present.

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7. ### avenger82Registered

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Thanks. So no discrepancy for the Oreca?
BTW: I've found GTE cars from this pack seem to have significantly more downforce than from GT3 Pack DLC. I know GT3 and GTE are different specs cars, but difference is quite significant. For instance I can take at full throttle Eau Rogue and also more easily turn 18 (the one after Blanchimont) on Spa. This is also possible in AC GT3s and on real on board footages(maybe with small throttle lift). On other rF2 mods like Apex mod GT3s it's impossible ,but they for some reason have more power and thus speed at the corners( they are also more bumpy and I think to lose traction easily). On GT3 Pack cars I need to lift throttle otherwise cars oversteer and usually cut track. All setups where close to default.

Also I've found Enduracers' LMPs have much more traction, even at lowest wings settings. They just stick to the road which seems unrealistic.

Last edited: Jul 5, 2018
8. ### RonnieRegistered

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Because GTE have significantly more downforce compared to GT3.

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9. ### avenger82Registered

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I think it may be an explanation for this mystery

Last edited: Jul 5, 2018
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10. ### Shawn JacobsRegistered

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@mclarenf1papa I look forward to hearing how your testing goes following the patch, do you think you will be able to post some follow up results now that the issue should be fixed?

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11. ### mclarenf1papaRegistered

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I did a brief test yesterday. While I didn’t really optimize the setup (though I did change it), I got it to about a 4.7 CL*A and a 4.1:1 L/D, which would still be too low. Will do more testing at some point.

12. ### Sherwin92Registered

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I'm still following this with interest, even though my knowledge of aerodynamics is quite limited. So to me, a noob on the subject, it sounds like the only "working" aero package was the low DF upgrade and whilst the others could certainly be used, they didn't give the aerodynamic efficiency they should have?

I look forward to seeing if this has been resolved with the update, because the LMP2 car is hands down my #1 weapon of choice.

13. ### avenger82Registered

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I'm also a bit disappointed because was expecting such issue would be addressed in the recent update. Especially that it was publicly raised here and on RD forum. In recent blog, S397 said they put a A LOT of work with real racing team to tune and validate Norma LMP3's physics, but I didn't see the same specifically for Oreca 07, but I know physics and specifically tires were updated for all cars in Endurance Pack.
I also don't have enough knowledge about aerodynamics, but from what @mclarenf1papa said L/D ratio should be around 5:1 but is still too low (4.1:1).
@Marek Lesniak can you please confirm/respond to that?

14. ### Marek LesniakCar TeamStaff Member

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What I can say, is that obviously we can't share any data we work with. Besides, discussing single L/D value for a car with different aero packages, leads to nowhere. Higher L/Ds are typically achieved at lower downforce aero packages. But for such a car, you need as much downforce as possible for a given track, which means, higher wing angles, added dive planes. All that affects L/D noticeably.

But if some of you guys have proper aero data taken from a wind tunnel (not just a single L/D value from a YouTube video), for various aero setups and ride hights, we can have a private discussion and see if it's any different compared to what we have

15. ### mclarenf1papaRegistered

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Well, to be totally fair to what’s been presented in this thread, the “single L/D value taken from a YouTube video” is from a picture of an excel test sheet of the Oreca 07/Acura ARX-05 at Windshear. A number of ride height points are fairly easy to read. The highest easily readable ScZ is 5.371, corresponding to an ScX of 1.17 if I recall correctly (but as Windshear has no correction for rolling resistance variation with load, that number is more realistically in the region of 1.11-1.13). Other ScZ’s easily read are 4.723 and 4.824. I also have anecdotal evidence that even the Riley LMP2 has a higher ScZ than 4.7. Additionally, I’ve worked on previous generation LMP1 and LMP2 cars with much more downforce than the current RF2 version of the Oreca (and numbers in-line with what I’ve mentioned above).

16. ### Marek LesniakCar TeamStaff Member

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I don't see any wind tunnel data here in this thread. Just a mention of a YouTube video.

17. ### mclarenf1papaRegistered

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Which has a shot of a computer with Oreca 07/Acura ARX-05 wind tunnel data from Windshear in it....which is the data I’ve been referencing.

18. ### lordpantsingtonRegistered

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This looks interesting:
https:// youtu.be/ anJ8KCNIH6U? t=128

edit: had to add spaces as it kept embedding video without timestamp.

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