Blockers and cats
megaoptimus,
I just have my intake in the vicinity of the cat shield, I haven't done anything to wrap that area at all. Where I am in CA it may get into the 30s, but never really cold and just having it resting on the cat shield is fine for the coldest temps when combined with the air blockers at the lower intake grills.
See:
http://fungiart.com/insight
In weather colder than 50s and/or cold and foggy (like in the mtns sometimes) the combination of warm air blockers (described at the web site) for the lower grill and the warm air mod (which I'll post soon) is sufficient to give me same mpg as on a hot day (80s).
If I drive with just one or the other in sub 50s, then I see some drop. I would say that the most important mod (if you are doing just one) is actually the blocking of the cold air flow into the engine area. I have the detailed data at another location (I'm out now). My recollection is that when I drove with just the blockers I did better than just the warm air intake mod for any given cold temp for faster speeds (>30-40 mph).
That makes sense to me. With the grills fully unblocked you are blasting cold air through the grills and over the engine filling the compartment with cold air. This has a big impact and is shooting cold air all the way to the back by the cat where you take the air with the warm air intake mod. At low speeds, then this problem goes away pretty fast.
At really low speeds, then the blockers aren't doing much because there isn't much air flow to block, and then the cat area warm air intake dominates.
I have driven even when it was hot with both the cat area warm air intake and the blockers, because I forgot the blockers were there. It was in the 80s, not super hot, but it did bring up the IAT more up in the 120s I think. Nothing bad happened. It also wasn't super hot.
I have seen no adverse impact of having the air pulled from near the cat shield even in high 80s and low 90s ambient. I have not yet driven in hotter temps.
It is much 'safer' to keep this year round, because it leave 100% of the air flow to your radiator and to your AC condenser.
FYI: I rarely if ever seem to have the engine temp get hot enough to want the fan, even on hot days. We just burn so little gas that it isn't ever a problem.