Do Flat Floors Slow You Down?

nasanu
You are missing that simply having mass puts a limit on speed. This is a law of physics and nothing you can talk your way around. Sure is an absurdly high limit, but a limit. Why can't you accept that? Anyway I tire of this. Chose to believe what you will.
Click to expand...
None of which has anything to do with flat floors which is the topic of the OP. There is however a place to discuss general physics right here:
[URL="https://www.gtplanet.net/forum/threads/update-1-06-possible-changes-to-the-physics-general-physics-discussion.306774/"]The Place to Discuss General Physics[/URL]
 
nasanu
Did YOU watch it? There is nothing on the video that matches what you are saying from what I have seen. All three parts are on youtube, can you find the bit you are talking about?
Click to expand...

Do you understand what the driver and narrator says ? He made lots of comments while the onboard driving the R34 shown ( portion with 2 onboard cam shown top/bottom )

The time also shown for a section of Tsukuba tracks, the one with diffuser is faster overall. He also noted that the R34 with diffuser has more stability under braking, less oversteer on exit, and should be about 0.20 to 0.30 seconds quicker at Tsukuba than without the diffuser/flat undertray. He also said the R34 without diffuser feels "floaty" under braking. He even added that with higher grip tires, the effect would be even more pronounced.


The diffuser test is after the R34 vs R33 test - last part of the video you linked.
 
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nasanu
You are missing that simply having mass puts a limit on speed. This is a law of physics and nothing you can talk your way around. Sure is an absurdly high limit, but a limit. Why can't you accept that? Anyway I tire of this. Chose to believe what you will.
Click to expand...

Sure. What's the limit?
 
Hmmm...all I know is when I uninstall the flat floor from the Viper ACR it gained almost or below or more than 70kph when I used it in Like the Wind then slows down when I installed it again.
 
Griffith500
I never said that. Stop being obtuse. Venturis, diffusers and such are generally not "flat". A pure, simple flat floor shouldn't change the profile of the car, so it can only decrease drag over a floor that isn't flat. If it's adding other shapes to the underside, or anywhere else, it's not just a "flat floor" anymore. This is the crux of the discussion.
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Just remember who put that crux in the discussion. ;)
Hint: (not me)


Imari
Sure. What's the limit?
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Available energy. ;) :lol:
 
CSLACR
Just remember who put that crux in the discussion. ;)
Hint: (not me)
Click to expand...

No, it was PD. We're interested in characterising precisely what PD's "flat-floors" are supposed to be, since they don't behave like flat-floors (alone). You did agree with the golf ball analogy, though.

nasanu
Great paragraphs. None of them related to you saying making something more aerodynamic increases drag though. Care to take another shot at it where you actually address what I said without trying to redefine drag?
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Why the attitude? What I said is true. Read here.

Making an object "rough" does reduce the aerodynamic efficiency of the surface flow layer. In some cases that can be beneficial overall by bumping the object into the turbulent regime "earlier". But, crucially, if a golf ball were bigger and / or traveled faster, or if it were smaller and / or traveled slower, the dimples would just increase drag as normal or have no effect, respectively. It's just a happy coincidence that golf balls sit in that sweet spot of Reynolds values where you can exploit the effect, and was discovered by accident (and later verified experimentally and theoretically).

The reason the golf ball was mentioned in the first place was to say that a rough surface is more aerodynamic, so a flat floor should create more drag. However, a flat, smooth floor on a car will always have less drag than an equivalent "rough" one, all else being equal, because a car is generally in the fully turbulent range when aero drag becomes an issue (Re of 10^7). The "regime-bump" won't work in that case, so the comparison is invalid.

I think you're just picking at details for the sake of it, and it's getting in the way somewhat.
 
Imari
Sure. What's the limit?
Click to expand...
Griffith500
No, it was PD. We're interested in characterising precisely what PD's "flat-floors" are supposed to be, since they don't behave like flat-floors (alone). You did agree with the golf ball analogy, though.
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I thought I used the gold ball analogy...

In any case, I can tell you what they do in the game easily. (didn't know people were still wondering that)
They add downforce as though they have a diffuser, some visually show diffusers and some don't, all perform as though they do have diffusers.

Is that the question or is there another one?
 
CSLACR
I thought I used the gold ball analogy...

In any case, I can tell you what they do in the game easily. (didn't know people were still wondering that)
They add downforce as though they have a diffuser, some visually show diffusers and some don't, all perform as though they do have diffusers.

Is that the question or is there another one?
Click to expand...

Figuring out what they do in the game is trivial. The argument was whether the behaviour is correct given the description. That's the question.
 
nasanu
You are missing that simply having mass puts a limit on speed. This is a law of physics and nothing you can talk your way around. Sure is an absurdly high limit, but a limit. Why can't you accept that? Anyway I tire of this. Chose to believe what you will.
Click to expand...

But we're talking about what limits the top speed of a car. Light speed physics doesn't matter, because no car will ever come close to it.

Mass certainly doesn't matter for top speed in GT6 and here's an experiment to prove it:

Take a stock Red Bull X2014 Standard to Route X. Adjust the gearbox to allow a top speed of 400 km/h or more. Do a lap and make a note of the top speed (the downhill part doesn't count).

Then add 200 kg of ballast to the car. This equals a mass increase of 35%. If mass limits the top speed then surely an increase of that size would be noticable. Do another lap and make a note of the top speed.

Here's my results:

Run 1: 395 km/h
Run 2: 395 km/h

Conclusion: Mass is irrelevant.
 
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This thread is so funny. So many physicists on this gaming forum :sly:.

I'm probably the only guy on this board that owns a car with flat floors (Lotus Exige), and I have the internal documents from Lotus explaining the reasoning for them, and the differences with, and without them. But I'm going to let all the physicists handle this :lol:.
 
Griffith500
Figuring out what they do in the game is trivial. The argument was whether the behaviour is correct given the description. That's the question.
Click to expand...
Of course you can't find your non-trivial questions answer if you can't answer said trivial question.
If said trivial question is trivial, both questions are trivial also.

;)

@UltimateLurker - I own a flat floor car too, and I have Lotus diagrams from the head engineers of the Evora explaining the universe.
But I won't share either.
 
UltimateLurker
This thread is so funny. So many physicists on this gaming forum :sly:.

I'm probably the only guy on this board that owns a car with flat floors (Lotus Exige), and I have the internal documents from Lotus explaining the reasoning for them, and the differences with, and without them. But I'm going to let all the physicists handle this :lol:.
Click to expand...

I'm surprised at the amount of people who come on to post "I know the answer. I'm not going to tell you but you're all wrong."

At least some of us are trying to share what knowledge we have with others. If it's wrong, then it'd sure be nice to know about it.

P.S. I seriously doubt you're the only person to own an Exige on the boards, let alone a car with a flat floor.
 
Imari
I'm surprised at the amount of people who come on to post "I know the answer. I'm not going to tell you but you're all wrong."

At least some of us are trying to share what knowledge we have with others. If it's wrong, then it'd sure be nice to know about it.
Click to expand...

It seems to be a common trait with any discussion of aerodynamics on the internet. "Oh look at all you amateurs. I know the reason, but I won't tell you. PS. You're all wrong. :sly:"

It gets kinda silly seeing this anytime aerodynamics is in question. Truth is most the people who seem to have "insider secrets" actually don't understand it one bit.

@UltimateLurker BTW I'd be willing to bet that the Lotus description is only technically right. Manufacturers include layman explanations. I'd put my money on the people who have actually studied this stuff answering the question in a detailed manner versus someone who claims to know all the answers because a book they got with their car explains it for the average driver.
 
Didn't feel like wading through all of the arguments to see if a response has been posted yet, but someone posed the question 'Are flat floors visible beyond the underside of the rear bumper?' (or something along those lines) and I can say that they do. It's actually disillusioning to have seen that the cars actually almost have flat floors to begin with, only with the mechanicals "painted" on. I get it, it would take up time to model undercarriages and then would likely use up resources to run the game--but still...:sly:
 
Ridox2JZGTE
The diffuser test is after the R34 vs R33 test - last part of the video you linked.
Click to expand...

Thanks, I'd missed that. My connection to youtube is rubbish and I use the video preview to skip over the video. When youtube does not respond it repeats images giving me the false impression that the video ended with the driving experience segment. My bad.

Griffith500
No, it was PD. We're interested in characterising precisely what PD's "flat-floors" are supposed to be, since they don't behave like flat-floors (alone). You did agree with the golf ball analogy, though.



Why the attitude? What I said is true. Read here.

Making an object "rough" does reduce the aerodynamic efficiency of the surface flow layer. In some cases that can be beneficial overall by bumping the object into the turbulent regime "earlier". But, crucially, if a golf ball were bigger and / or traveled faster, or if it were smaller and / or traveled slower, the dimples would just increase drag as normal or have no effect, respectively. It's just a happy coincidence that golf balls sit in that sweet spot of Reynolds values where you can exploit the effect, and was discovered by accident (and later verified experimentally and theoretically).

The reason the golf ball was mentioned in the first place was to say that a rough surface is more aerodynamic, so a flat floor should create more drag. However, a flat, smooth floor on a car will always have less drag than an equivalent "rough" one, all else being equal, because a car is generally in the fully turbulent range when aero drag becomes an issue (Re of 10^7). The "regime-bump" won't work in that case, so the comparison is invalid.

I think you're just picking at details for the sake of it, and it's getting in the way somewhat.
Click to expand...

You simply can not admit where you are wrong and try to defend yourself by being patronizing. That is 'why the attitude'. Again you write paragraphs without actually addressing what you were relying to. Even the link said nothing about aerodynamics being the art of increasing drag, it just went into detail about different types of fluid behaviors. Cant you just simply admit that saying things like dimples in golf balls increase drag was plain wrong?

I can see what you were trying to say, you meant to speak about different ways of decreasing drag, but you didn't and ended up saying the opposite. It would kill you to admit you were wrong it seems.


Anyway it seems this whole argument is about nothing. If the best motoring tests are accurate then PD's flat floor with diffuser is accurate. I just tested the racing 86, when the normal car hit 245 the flat floor car was at 233. And when I was racing in my normal floor 86 vs a room of guys with flat floor 86's I did not notice any difference in straight line speed, though their ability to corner better was obvious. Actually I didnt even know they had flat floors till one guy mentioned his PP and I questioned why mine was so much lower. I just put their better handling down to their tuned setup and my stock and there was no visible difference in straight line speed.

BM tested on short straight coming out of a corner which allows the flat floor car the most advantages conditions and there was still a few km speed difference. That makes my 12km difference in a straight line on route x seem accurate.
 
nasanu
Thanks, I'd missed that. My connection to youtube is rubbish and I use the video preview to skip over the video. When youtube does not respond it repeats images giving me the false impression that the video ended with the driving experience segment. My bad.
Click to expand...

No worries :) One thing for sure, having diffuser on a 300+HP stock R34 is good for 0.2 to 0.3 second at Tsukuba, that with front 'diffuser' undertray that only covers engine part and rear diffuser that covers rear wheel section to rear bumper - while the middle section is left bare. I still think that GT6 flat floor effect is exaggerated, maybe half the current effect is more closer to real life :P
 
nasanu
Anyway it seems this whole argument is about. If the best motoring tests are accurate then PD's flat floor with diffuser is accurate.
Click to expand...

Where is this diffuser you speak of?
original
 
The flat floor also comes with rear diffuser on some cars :) It's just PD being PD, the visual do not always represent what's in the car :lol:
 
Ridox2JZGTE
The flat floor also comes with rear diffuser on some cars :) It's just PD being PD, the visual do not always represent what's in the car :lol:
Click to expand...
We do a lot of imagining in this game. Ignore the visual camber on your car it doesn't work, ignore the visual flat floor without the diffuser and pretend it has one, ignore that high front ride height it actually behaves as if the front is lower:lol: It's no wonder bumper cam is so popular, you don't have to look at the cars when you use it!!:odd::odd:
 
Ridox2JZGTE
No worries :) One thing for sure, having diffuser on a 300+HP stock R34 is good for 0.2 to 0.3 second at Tsukuba, that with front 'diffuser' undertray that only covers engine part and rear diffuser that covers rear wheel section to rear bumper - while the middle section is left bare. I still think that GT6 flat floor effect is exaggerated, maybe half the current effect is more closer to real life :P
Click to expand...

Lets try this with an R34 at Tuskuba in game then?.. I'll do it tomorrow if nobody in a more awake timezone does it before then. If the results on say comfort softs are only a little bit better than BMs (allowing for the more complete flat floor in GT6 vs real) then we can say they are accurate. Or not..
 
nasanu
Lets try this with an R34 at Tuskuba in game then?.. I'll do it tomorrow if nobody in a more awake timezone does it before then. If the results on say comfort softs are only a little bit better than BMs (allowing for the more complete flat floor in GT6 vs real) then we can say they are accurate. Or not..
Click to expand...

You can't fit flat floor from GT Auto on R34 GTR premium ('02), but you can compare R34 GTR '99 with R34 GTR '99 Vspec. IRL, the standard model R34 GTR do not have rear diffuser or front flat undertray. You can test to see if PD do model the difference on both models. From my experience driving the R34 GTR '99, it has more oversteer than the Vspec, but that might also caused by the Vspec having A-LSD :)

And you might need comfort medium, I compared Advox Supra RZ '97 real life lap and in GT6, Comfort medium is the tire to go, very close.

For reference, Best Motoring Tsukuba lap record for R34 GTR ( non Vspec ) 1:06.28, while R34 GTR Vspec II 1:06.04.
 
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Crispy
It seems to be a common trait with any discussion of aerodynamics on the internet. "Oh look at all you amateurs. I know the reason, but I won't tell you. PS. You're all wrong. :sly:"

It gets kinda silly seeing this anytime aerodynamics is in question. Truth is most the people who seem to have "insider secrets" actually don't understand it one bit.

@UltimateLurker BTW I'd be willing to bet that the Lotus description is only technically right. Manufacturers include layman explanations. I'd put my money on the people who have actually studied this stuff answering the question in a detailed manner versus someone who claims to know all the answers because a book they got with their car explains it for the average driver.
Click to expand...

I didn't say anyone was wrong, I was merely marveling at people who have no real knowledge of the subject arguing about it. I'm no aerodynamics engineer, but I know a little ;), hence why I stay out of the discussion.

And the reason I don't post the Lotus documents is that people wouldn't believe it anyway, or they'd say it doesn't pertain to their car and just continue to argue for argument's sake. No need for me to get into that.

I will say this point of fact; in real life, flat-floors are made to help control air-flow and air-turbulence to get a desired effect (which changes depending on the goal of the manufacturer), and the shapes of the splitter, and diffuser are absolutely critical to how effective the flat-floor is. Basically, adding a flat floor without a splitter and diffuser is all but useless, and can have terrible consequences. Some of the earliest testing of flat floors on normal cars resulted in the rear wheels (in mostly RWD cars) lifting off the ground at high speeds.

There's my 2¢, and this thread is probably no better for it :).
 
Johnnypenso
Lotus Exige Owners Manual for anyone interested:

http://www.pdfuserguide.com/2012-lotus-exige-s-owners-manual/

http://www.productmanualguide.com/lotus-exige-owners-manual.html

Note: It also describes other top secrets like how they get the caramel in a Caramilk bar and the befuddling popularity of Justin Beaver...so use it wisely:lol:
Click to expand...

Not sure why you posted these links, the owners manual doesn't have any information on flat floors IIRC, but it does have some funny stuff about Porsche :).
 

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