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There is no "ram" part about this, The intake is going to suck in air at the exact same speed as it did before you put that funnel there. And more so the air doesn't travel fast enough through the funnel and into the intake to make it ram anything. Its just blocking the rain mostly from splashing up. And in essence you have limited the cold air that the intake can potentially bring in by blocking it all off, and bottle necking it with the funnel.

Wet days? Good idea.

Cooler days? I think you are limiting the air in a sense. noticable? Not much if anything.

Take a read on this:

Dispelling the myths about "ram air"