weight or power?

  • Thread starter Thread starter AJ11
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I don't think that weight has as much effect in GT as it does in reality. Going for more power will probably turn out fine 95% of the time, as it doesn't really hurt your low end speed, but it helps your high end speed. It would probably take some extended testing to see how things really work in GT5.

Weight ballast changes PP based on ballast position because it changes your weight balance (and the game considers 50/50 to be perfect, which is wrong since 50/50 will only hurt a car with tires sized for 30/70). Your moment of inertia might also be calculated in PP.

Aerodynamics raise PP because it is modeled incorrectly and there are no disadvantages to increasing downforce except for an almost trivial increase in drag. In reality, aero probably shouldn't affect PP as it does in game since you would have to work hard to find the right balance between downforce and drag to minimize lap times.




Yes, the spoiler is there. The difference is how the air moves around it. Think of it like a helicopter or a fan blade; the blade is at an angle and moves quick enough to push the air down, and push it's own mass up (explained by Newton's 3rd law of motion). With "downforce" you are doing the exact opposite of a helicopter; you're forcing the air up while forcing the car down. Now, if you were to change the angle of the blades of a fan, the air would be pushed down at a steeper angle, and be pushed down quicker. Same thing with a car's aero kit, the steeper the angle, the more air you'l force up, and the greater the downforce on the car. Then comes the drag issue; if you were to turn a fan blade 90 degrees, it would just push air around, not really up or down. It's also needing to push a LOT more air, which is what "aero drag" comes from. The greater the downforce you have, the lower your top speed and acceleration (due to drag), though not by much. The reason heavier cars are slower than light cars with higher downforces, is because of inertia; heavier cars have more inertia, because they have more mass. It is harder to push something that is heavier (more massive) than something that is lighter (less massive). What slows down a higher downforce car is the aero drag, or resisting force.

It's amazing what the great Isaac Newton can teach you about racing... :)

This is an excellent description except for the drag part. The drag doesn't come from pushing more air, as the angle doesn't change how much air is pushed. You're always going to push every particle of air in the entire atmosphere (though, at some distance it gets so small that we just discount the effect). Drag comes from three things:

1. Skin friction, this doesn't really change with downforce.

2. Flow separation, the chance of having separation increases with increased angle of attack. When flow separates, it can no longer exert pressure on a surface. So you have high pressure air pushing the wing back and nothing behind it pushing it forward, this is felt as drag.

3. Induced drag, this is drag that comes directly from downforce and manifests itself as vorticies on the edges of aero parts. It rises with the square of downforce.

One great thing about the Newton's Law analogy is that you can take it further. F= ma; a has a magnitude and direction, so changing the direction of flow requires a force. This leads one to realize that the radius of curvature has an effect on the aerodynamic force generated, however there is a limit to how much you can curve things, once the flow separates, you've gone too far.

All of that said, downforce in GT5 does not come with harsh drag penalties like it does in real life, and this is why downforce must be regulated with PP. If PD were to use a more realistic aerodynamics model, then we could probably adjust aerodynamics without worrying about PP.
 
One thing that no one mentions, except maybe one guy, is more downforce=lower top speed. But faster through the corners. So if you're driving on a high speed track, like Daytona, or even Monza, try not to set the downforce too high. But for the Nurb, try 50/50, or maybe even 60/40.

I'm not an engineer, so I can't explain aerodynamics in fully detail. But yeah, more downforce=faster through corners, slower on straights and less downforce=slower through corners, but faster on the straights.
 
This is an excellent description except for the drag part. The drag doesn't come from pushing more air, as the angle doesn't change how much air is pushed.

Yeah, I didn't describe drag so well... Sometimes I'm bad at explaining things, sometimes I nail it right on the head.

@AJ11:

"Doesn't max aero minimize top speed? I.e. the veyron drops it spoiler to be lose on the road!"

Yes, increasing downforce WILL slow your top speed and acceleration, but not by much. Too much downforce really only becomes a problem for two reasons:

1: You set the X1 to maximum downforce. Once the car reaches about 280-290 MPH, the car will start scraping the ground (unless you tune the suspension), and you'll lose a LOT of speed. Otherwise, downforce BARELY affects your speed noticeably; really only if you've got a race car it's noticeable. You can slightly turn down the downforce from maximum to give yourself a few extra PP's, but it's really all down to driver preference.

2: The track you're racing on has very little corners, or very wide corners. Tracks such as SS Route X and Route 7, Daytona (oval), Indy (oval [though you may need some extra downforce on road cars for Indy]) and some custom tracks. The downforce will only affect you negatively, for there's no use for it (unless you have EXTREMELY low grip, and turning will cause a spin out [which is really only possible if your tire strength has run completely out]), and will RUIN your top end, especially on Route X.

As for the Bugatti; James May explained it well. Air has different properties, or "thicknesses" at different speeds, so changing the position of the spoiler at a higher speed will actually give the car better down force than the lower speed position. I'm not sure if GT5 actually incorporates these sort of physics. Part of what aero kits do (spoilers, etc.) is increase stability, though not all will, necessarily. downforce increases tire grip, so if the Veyron's spoiler stays down at 250 MPH, the car would be WAY more likely to lose control than with it up. This is why you need a key to lock the spoiler down in real life, as Jeremy Clarkson demonstrated on a Top Gear race, where we tried to see how quick he could go on the Autobahn while racing May and Hammond in a plane.

Am I explaining too much and going too far off topic?:scared:
 
No that was great. And I seen both those episodes so I know exactly what your talking about. POWER! Lol. but.they did a lot of planes vs trains vs boats vs cars.
Thanks again.
 
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