a pod in the engine bay is better than an airbox. nizgirl got her ca20e pintara dyno'd immediately before & after the installation of her pod, and she got a 3 or 4kw gain.
when you are driving, a vacuum affect takes place under the car, sucking air from the engine bay (hot air included) so its probably not so bad.
unless you had extreme temperatures under the bonnet, the pod is better because it is sucking more air. the whole idea of more power is as simple as more efficient combustion, which more air (or less fuel) will help out with more efficient combustion. to a certain extent anyway.
of course, sucking cold air is better. cold air is denser, which in turn means even more air.
as for the so called ram effect. i guess there is such thing. but most people just assume that if they stick the pod in an open area at the front of the car, they will achieve a ram effect. this isnt so. what the ram effect is is when the air is compressed due to it forcing itself up against a panel or maybe even the windsreen. so you have something like this...
air toward car ---> * <---- air bouncing off panel /// <- panel
so you have air moving toward the car. and air bouncing back (so to speak) of a panel. which in turn compresses it at the point where the asterisk is (*) which is where you should place your pod, or your inlet to you cold air setup.
i hope that helps you out a little. it is now just a case of how far you want to take it.
something to think about though is a premade shieled pod & silicone hose setup. they are less than $150 and they will do the trick. i have attached a picture. i can get them for about $125.
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