Originally Posted by its840
power wise is there any diff?
Both have the same purpose. Deliver cold air. FWI is probably better because it gets the air from a cooler area of the car. If the restriction were the same for both (as it should be hypothetically) then no real difference.
Let'* go with real examples.
Willwren has a CAI with heatshield box built around it. At his currently known top speed of 156mph there is tons of cold air running through the engine bay. However when he is stopped in traffic he might notice temps rise slightly in the CAI with the engine bay heating up. He still has better flow and the temp shouldn't be any hotter than a stock setup.
Lux put in an FWI, it gets the air from a remote location in his fender. He does not need a box because his fender is the insulating box. At his current max speed of about 128mph his engine bay is cool similar to Wllwrens, but his filter is taking air from the fender. At a standstill during his commute home he will pick up heat from the road and his engine bay to some degree. However not as much as a CAI setup is expected to pickup.
Personally I believe it to be a matter of opinion and availablity. When it matters you are moving and the cool air is available. At this point in the year ...being in New England and Oregon..Lux and Bill are probably both happy since the weather cooled down.