Why are carmakers blocking the lower grille, not the top? (OEM active grille blocks)

[DonR]

( Admin Edit: split this thread off from GM describes 2013 Chevy Malibu ECO aerodynamic tweaks (Cd ~0.28) )

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Around here grille blocks start at the top & work their way down. Why do you suppose OEMs have an aversion to blocking the top parts of the grille? Both Ford & GM have blocked the lower parts.

[Daox]

Originally Posted by DonR

Around here grille blocks start at the top & work their way down. Why do you suppose OEMs have an aversion to blocking the top parts of the grille? Both Ford & GM have blocked the lower parts.

The Focus grill is almost entirely blocked on the top. The only real opening is the bottom (which has an actuated grill block).

[MetroMPG]

Could also be a design practicality: more room to install actuators & linkages in the lower grille area.

[aerohead]

Originally Posted by DonR

( Admin Edit: split this thread off from GM describes 2013 Chevy Malibu ECO aerodynamic tweaks (Cd ~0.28) )

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Around here grille blocks start at the top & work their way down. Why do you suppose OEMs have an aversion to blocking the top parts of the grille? Both Ford & GM have blocked the lower parts.

When all the loose Wal Mart plastic bags clog the fake grille underneath the engine will still have a source for cooling and combustion air.

[NeilBlanchard]

Most of the upper grill on the Honda Fit is blocked.

[ecomodded]

On my car I will be blocking the bottom, the top is only slightly higher then the bottom grill. There is more rad surface area behind the top grill as the bottom grill is partially lower then my radiator.

[Phantom]

I assume on of the reasons is to help keep the air coming into the engine cooler for performance reasons and not FE.

[ecomodded]

After thinking about it diesel cars run cool,my car is a diesel..
I need a better plan then blocking the bottom grill.After a bit more consideration i have deduced that the air going off the bottom blocked grill would either go under the car or against then into the top grill. That can't be much of a improvement. With the top grill blocked the air stands a chance of joining in with the main air flow, that sounds like more of a improvement.

[VBOD]

TIC, I'll take a SWAG at it. Assuming they are blocking the grill from the bottom up. Maybe they are assuming that the air next to the ground is hotter than air above it. No, really, on a hot day the air closest to the heat source (asphalt) is going to have more heat content than air just 18" above the asphalt. Lots of hand waving in this assumption but...

[suspectnumber961]

The real big WHY.

WHY do many of the newer cars have these BIG aggressive looking openings in the front?

Most of them are simply painted black to look like openings?

Stylistic hell.....?

Halloween is coming? The PUMPKIN look?