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Discussion Starter #1 (Edited)
OK, I have a basic knowlege of EFI systems. Most of the buildups I have done has been carbureted, so maybe you EFI gurus could help me out on this one.

So the EFI system uses the mass air sensor to measure the air coming into the intake so it can add the correct amount of fuel to make a 14.8:1 air\fuel ratio(correct me if I am wrong on that it has been a while). Now my question is, does it measure air density, or just volume? If it measures volume only, and I install a CAI on my box, would the denser air then cause a slight lean condition (splitting hairs I know, but stick with me here)so when the o2 sensor measures the exhaust, it will compensate by adding fuel. But if it measures density, the computer would compensate, adding more fuel thus it would not improve fuel economy.

So long story short, my question is: Do our boxes measure intake air density?

This is the kind of thing I think about when I drink lol
 

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Intake air density would be something like a MAP system(Manifold absolute pressure). Hondas use a MAP sensor instead of a MAF. Our systems measure the air going into the intake manifold. The MAP sensor on a Honda measures the pressure of air already inside the manifold. Hope this didnt confuse you
 

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Discussion Starter #3
Thanks, that makes sense. I was looking at alot of CAI's lately, and noticed that half of them claim increased fuel economy, while half never mentioned it, but theoreticly it shouldn't be able to improve fuel economy, because the more air goes in, the more fuel the EFI will spray in so it keeps the proper air\fuel ratio. Power increases are obvious, but I dont see how it can increase fuel economy.

I guess it really doesnt matter, I just think about stupid things like this lol.
 

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The maf sensor measures air flow however just by adding cai wouldnt increase density with no forced induction the air density is basicly the same if you drive up here to denver youll see and feel some thin air. cai just reduces restriction. heres a comparison if your cai/air box becomes cloged minorly the pcm will richen fueltrim to keep the power up reguardless of a/f ratio. so by freeing up air flow in theroy the engine can actually use a hair less fuel for more air. I hope you can get what I'm trying to say cai could use less fuel by making air flow less restrictive more readily available.
 

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it will only use less fuel for the first few hundred or so miles, then the fuel trims will start kickin up to the point where the intake isnt really doing anything but making noise. This is why I used to reset my fuel trims even before I put the turbo on. Its not as drastic without forced induction, but still is a gremlin to performance on these economical boxes
 
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