[aerohead]

Originally Posted by pasadena_commut

Sure, on an unmodified car that makes sense. However, once the grill blocks go in, is that position necessarily still optimal, assuming it is still possible. On my Protege5 the engine intake is through a space under the leading edge of the hood. It's hard to describe this, but it is sort of on the upslope of the front end of the car. If the upper grill was blocked aerodynamically the intake would still be possible but probably the air pressure there would be greatly reduced by better flow over the front. For our Subaru Legacy the engine air intake is 1/4 of the upper grill (which is split into 4 parts by a sort of "+" shaped member). There at least one could block 3 of the 4 quarters and I think the engine intake would be little affected as the ram effect at speed would be unchanged. If the entire upper grill was blocked the intake would have to move, else it would be literally sealed off, at which point the question becomes, where to move it to. In this regard, brucey avoided the whole issue by blocking the lower intake:

http://ecomodder.com/forum/showthrea...html#post46349



Ok

The upper grille-block essentially creates an airtight duct common to the lower grille opening.Stagnation pressure is still communicated through the duct to the inlet above.Since this air is harvested at the point of maximum static pressure,by moving the inlet elsewhere,you potentially re-locate it to an area of reduced pressure as demanded by the Bernoulli Theorem.