[basjoos]

Since the underpanel covering the bottom of the engine compartment keeps radiator exhaust air from exiting out the bottom of the engine compartment, I exit most of this air out through the front wheel wells where the low pressure created by the spinning wheels helps to pull the air through. A smaller amount of radiator exhaust air also exits through the covered central tunnel where it cools the exhaust pipe and cat, eventually exiting at the right rear wheel well.

I'm not trying to increase radiator cooling, as the whole point of an adjustable grill block is to tailor the cooling air flow (and its inherent air drag) to match the cooling needs of the engine. Since the openings from the engine compartment to the front wheel wells are much smaller than the original cooling opening out of the bottom of the engine compartment (now blocked by the underpanel), I use the slight suction created by the spinning front wheels to help move air through the engine compartment. This allows me to have plenty of cooling air flow when the adjustable grill block is open, but limited air flow when the grill block is closed and acting as a flow restrictor against the pull created by the spinning wheels. Most of the time my grill block is closed or barely open.