Why do a grill block when you could put excess air to good use?
 

Stick one of these in front of or behind your grill and you will get the same effect as a partial grill block and some energy back to boot.


BPE14 TURBO STAND-BY ALTERNATOR from Aircraft Spruce

Sounds like a good idea but would it be really?

As per the specs, it only outputs 6 amps @ 85 mph; not a great speed for hypermiling, not to mention the probable increase in drag upfront.

because its $800.

Mostly because you want the car to go through the air as easily as possible. If its spinning a turbine, no matter if its in a grill or strapped to the top of the car its still spinning that air blender up.

Aerodynamics are one thing, but the reason most of us in Northern climates use a grille block is to have the engine warm up faster in sub-freezing temps.

If it is in the grill and spinning the turbine it is creating resistance to the flow through the grill, just the same as a grill block. This forces more air around the car and thus helping it cut through the air more cleanly.

There ain't no free lunch and it takes more power to spin that thing. Grill blocks BLOCK the internal flow; this does not.

Hey, I got one of those on my plane!

A 100% grill block blocks internal flow. A partial grill block impedes it. The turbine will impede it as well. Its not a free lunch. Its taking a bite out food you have already paid for before it rots.

A grill block giving the same reduction of internal flow as the turbine will reduce power required more than the turbine would have produced. Unless the turbine is greater than 100% efficient. Give up on this one.