Keeps out the berries and leaves though! think Macadamia nuts and Mini Figs and you have Aussie tree droppings in mind! Some mornings required cleaning off the wiper blades with one hand and covering the already full grill with the other.There will be no performance difference either direction. The cowl is vented at the bottom, so it doesn't matter reference pressure and what not.
My own fault of course for buying an in town heritage shotgun house way too old to have a garage or driveway.