Cold Air Intake effect on gas mileage?

CAI does nothing to the gas mileage. It neither hurts nor helps.

CAI does not push more air into the cylinders, it just gives colder air into them. A S/C forces more air.

If you put more gas in the engine, it doesn't do any good unless you have more air to go with it...that's the idea behind a turbo and supercharger...they force more air in with the gas. A CAI cools the air goiing in the engine...cold air has more molecules than hot, so in a sense, it is "more air". I believe you get 1% HP increase for every 11 degree drop in temp. This combined with a less restrictive pipe and filter gives a horsepower gain. If you can keep your foot off the gas, (most people don't...after all you bought the CAI for power) you will get a small (1 or 2 MPG) increase. This statement is based on my last 3 cars...Accord Coupe, Celica GT & RSX-S all of which I installed a CAI.

This is my experience from 12 years of driving with CAIs.

Oldster is right. You will not notice much difference in gas mileage as you're not changing the amount of fuel that is injected into the combustion chamber. Theoretically, it could help, but as he said, after you do a mod like that, your foot becomes a few pounds heavier out of no where which negates any gas mileage gains you could have gotten. It really won't give you too much HP gain either... sure its bringing in less restricted air flow, but that does not mean MORE air... just means better throttle responce and maybe a bit more of a pull top end. I am a fan of cold air intakes, but I truely feel that they're more cosmetic or for a better sound rather than true performance mods. I may get one myself, but I'll wait until aftermarket companies come out with other choices.

The how much of a performance boost would I get with CAI (in horsepowers and torque) in tC? I was thinking about installing it in the dealers, when its available.

i think it is somewhere around +10hp, give or take a few

Typically, you can get 5 - 10 hp increase. What concerns me on the tC is that the stock air box is already vented to the fender. This means you already have cold air benefits. You will still benefit from a less restrictive filter and pipe, but I doubts that the gains will be as much as other cars. There is a sound "benefit". If you like the sound of "power", the CAI will add sound to your driving experience.

Good post IAMASAF! I'm gunna check that out tomorrow and see how it looks... i'll make a "how to" if i think it makes sense!