What's the point of flat floors?

[Operation Ivy]

If they're going to have a negative effect the mod should be "remove flat floors"

 

[Dan]

What negative effect? They're supposed to help make your car more aerodynamic/increase downforce.

 

[Azure Flare]

Supposedly, a flat floor is meant to seal the underside of the car for better aerodynamics, and they all come with a diffuser at the back for added downforce and reduced drag.

Whether or not this actually has any effect in GT6 is debatable, but my Boss 302 looks damn cool with a diffuser!

 

[Operation Ivy]

What negative effect? They're supposed to help make your car more aerodynamic/increase downforce.

When I put it on my Stingray the top speed went down even though it's the only thing I changed
No matter what I do to adjust top speed it's always lower with the floor on

 

[amzgspider]

I may be wrong but I would guess the decreased top speed is due to the added down force however the increased handling should out weigh the loss of speed.

 

[Fuzzi0n]

It shouldn't really lower the top speed, if anything it should help with that because you've got a nice uninterrupted surface underneath the car. Might be worth having a play with the ride heights and rake to see if the flat floor affects that - not sure how good their aero model is but you could set the car up in a way that the floor wont generate any downforce.

Anywhere else, they're better, you can easily generate a decent amount of downforce with almost no drag penalty.

 

[Exorcet]

In GT5 no aero parts besides the rear wing even changed performance. From what I've read on GT6 this is still true.

Adding underbody panels should have no noticeable negative effect on performance. This should be true even taking into account the addition of a rear diffuser that produces downforce. If your car is slower with panels it could be a bug.

 

[Mini Stiggy]

Here how the work in GT6:
They add 20-30pp
They reduce top speed
They give you more downforce
90% of the time in circuit PP racing, you'll be faster without it(Say your M5 is at 550pp and it's pretty competitive, you add a flat floor, now say your at 575pp. But then you must take off 25pp of power to get back down to 550. The better handling you get is outweighed by the extreme loss of power)

 

[Azure Flare]

Mulsanne's Corner
A diffuser allows the air traveling underneath the car a place to expand and decelerate back to road speed as well as providing wake infill. As the air enters towards the front of the car it accelerates and reduces pressure. There is a second suction peak at the transition of the flat bottom and diffuser. The diffuser then eases this "high velocity" air back to normal velocity and helps fill in the base area behind the race car making the whole underbody a more efficient downforce producing device.

Understand that a true flat bottomed car (one without a diffuser) will produce downforce in and of itself when run in rake. Essentially the entire flat bottom becomes one large diffuser. It too has two suction peaks, one upon entrance, the second at the trailing edge of the flat undertray. A diffuser acts to enhance this underside suction, it acts like a pump, encouraging better flow under the car.

One thing to note is that the rear wing interacts with the diffuser "driving" it. The proximity of the low pressure side of the rear wing to the diffuser encourages better flow-through for the underbody.

 

[ace004]

Here how the work in GT6:
They add 20-30pp
They reduce top speed
They give you more downforce
90% of the time in circuit PP racing, you'll be faster without it(Say your M5 is at 550pp and it's pretty competitive, you add a flat floor, now say your at 575pp. But then you must take off 25pp of power to get back down to 550. The better handling you get is outweighed by the extreme loss of power)

This. Flat floors are broken in game.

 

[Doge]

Floors produce downforce, especially with minimal ground clearance (ground effect makes it dramatically more effective). Floors tend to be the only non-penalised aero effect- wings and splitters come with a huge drag penalty proportional to the downforce you gain. Floors can produce a lot of downforce (large surface area) at very minimal drag penalty (or in fact, drag reduction).

I feel in GT6 the downforce they create is less than realistic, and the PP increase is disproportionate. Also in most of these cars, the drag should be reduced, not increased.