I have always thought the air flow was too weak on my car so I took a look through the grille on my '05 (late production) and only two of the intake plenums were opened and covered with the mesh. The middle plenum was uncut and totally sealed while the two open plenums were completely plugged with bugs, leaves and road crud. I cleaned all the crud off the mesh with a stick and a wet rag, but I need to pull the grille and clean everything thoroughly when I have more time. This looks like another cleaning chore that I will need to add to my list on a yearly basis. When I pull the grille should I cut open the center plenum or did the factory leave it uncut for some reason?
Tonywa28 said:The ribs form three plenums that feed the intake to the climate control system. The openings to those plenums (at least on my very early car) were considerably smaller than the plenums themselves. The holes just weren't cut with much care. One other sort of jungle math bit - I'm pretty sure the vent hose on the output side of the climate control is 4" diameter yielding 12.5 square inches of area. For my car (the only example I have ) the inlets in the ribs probably had more like 8 or 9 square inches (approx. 1.5 *2* 3) of total area. Again the cut-outs did not "port match" to the plenums very well. Imagine a big carb vs. small carb. Bigger venturi gives more CFM or try drinking coffee through a coffee stirrer. I think I'm on solid ground here, but am open to opinions.