"cold air intake" piping size

well, since i seem to be on my own here, i ordered some 4 inch aluminum pipe and two 90 degree silicone couplers
I'm going to go straight out into the fenders (already moved the washer reservoir) and install the 90s in there, facing up and to the front of the car
that should keep the road debris out and work as a ram air set up...sorta
then run a straight tube into the air cleaner

easy peasie lemon squeezie