Motor Vehicle Dynamics: Modeling and ... - Google Book Search
Pgs 104-105: "...internal flow in the engine compartment can account for about 13% to 20% of the total drag..."
Incidentally... Pg 110: "Shape drag is what remains of the drag if the contributions due to friction drag and induced drag are removed and, in the case of road vehicles, it is mainly due to the wake."
OK instead of me transcribing a whole book for you, why don't you just read from my link in particular pgs 89-132.
Leading Edge #21: Remember Your Cowl Flaps "...All that air flowing through the engine compartment, though, also creates a tremendous amount of drag, which will rob you of cruise airspeed."
Compatibility of Automobile Interior Space With Low Aerodynamic Drag Body "...Since engine cooling flow is one of the dominant factors among aerodynamic characteristics, resistance due to internal flow in the engine compartment are also explained."
http://www.dd.chalmers.se/~lelo/rvad...on-to-drag.pdf No Adobe on this computer... what does it say?
As far as the grille:
Image of a Fluid Flow
As shown in Fig. 11.87 there is a stagnation zone around the front of blunt objects. Whether the grille is blocked behind or in front, the effect is largely the same, as aerohead noted in post 4.
I have also read that headlight buckets in older style vehicles didn't really hurt aero because of the stagnant bubbles in front of them. Sorry could not find web links for that.
Now it's your turn.
