So far, so good.

More O2 than what? The thing is, very hot air in Death Valley (dry and with very high barometric pressure) will be considerably more dense and contain much more O2 than very cold air at say Independence Pass in Colorado (also dry but with low barometric pressure).

So now we get to the crux of the situation; most folks assume that engines measure the amount of air entering the engine by volume or by the position of the throttle butterfly valve. Nothing could be further from the truth. The volume of air and/or the throttle position is completely irrelevant; the amount of air that enters your engine is measured by weight, and the engine control unit is very capable of determining how heavy the inbound intake charge is, and therefore how much oxygen is in said intake charge. Said another way, from a fuel economy perspective, at any given temperature and humidity level, it matters not how dense the air is, the engine will recieve the proper amount of fuel for the air entering at all times and deliver the same fuel economy for any given type of driving.

To sum this all up, the greater the weight of the air downstream of the throttle body, the greater the amount of fuel the engine will recieve, and the greater the amount of power the engine will generate.

When the intake charge is above roughly 40°F, there really isn't a significant difference in how well fuel vaporizes in a modern fuel injected engine, however, below that temperature, the differences can become pronounced. Cars that have CAIs and/or have had the coolant plumbing disconnected to the throttle body (if so equipped) can see dramatic losses in fuel economy compared to an otherwise identical but unmodifed car when driven in the same environment.

Make sense?

 

Wow, lots of great info. So while i am getting it i might as well soak up some more if your willing.

So is it the fact that the CAI is bringing in a larger amount of air? That is the determining factor in why you are getting more HP and torque. Not the fact that the air coming in is actually cooler from the wheel well then the engine bay where your original air box is located.

And to answer the one question you had above. I was told that due to the fact that colder air was more dense then hotter air that it would therefore contain more 02 then the less dense hot air.

And lastly, if the air temperature is not a factor, why do they bother naming them cold air induction systems rather than just air induction systems? May be just a marketing tool and not really something you can answer, just curious. And on that subject why bother making heat shields for the ram air systems to try to avoid as much heated air from getting through?
The one for my Miata is ram air as that is the only kind i have seen. And everyone says i should get a heat shield. Although i have not bothered to get one of just make one myself.

Thanks again.

 

A few comments that may help clear up your questions:

• Given that the throttle body is the primary limiting factor in virtually all port style fuel injected engines, I personally think claims of "greater volume" due to the installation of a CAI are dubious at best. Said another way, vehicle engineers are pretty good at matching the capacity of the intake on any given engine with the needs of said engine. I know lots of folks claim the factory intake on their car is restrictive, but I suspect the number of instances where those claims are actually true are less than ten percent of the total.
• At any given "Density Altitude" (a formula used by pilots to determine how dense the air is they're about to take-off in which takes the barometric pressure, the OAT, and the relative humidity into account), an engine that is fed a cooler (more dense) intake charge will generate slightly more power than an otherwise identical engine with a warmer intake charge. That said, many (most?) vehicles these days are built with the ability to source the intake air from the cool air stream in front of the heat exchangers (A/C condenser, oil and tranny coolers, and the radiator), I mean geez, even our old late 1990s Chrysler minivan had an air box that would take air from the front after the engine had warmed up sufficiently. Might the air from a CAI be a bit cooler still? I suppose it's possible, but to what degree?
• As for colder air being more dense than warmer air; that is only true when the density altitude outside the vehicle is constant. If you're comparing the hot summer air in Death Valley to the cold winter air at Independence Pass, then the hot air in Death Valley is way-WAY more dense; this goes back to the density altitude thing. Think about it this way, if you were driving across Death Valley (-282' MSL) on a day when the temperature was say 120°F, the Density Altitude would be roughly equivalent to the air density at 2,000' MSL where the OAT is 59°F. The flip side is that the density altitude at Independence Pass (12,095' MSL) on a day where the OAT is -20°F would be roughly equivalent to the air density about 10,500' MSL at that same 59°F temperature. This is a long way of illustrating the fact that just because air is cold, it isn't necessarily dense.
• When I wrote that the air temperature (above 40°F) is irrelevant, I meant "irrelevant from the perspective of fuel economy"; for the power equation it is definitely relevant (although the degree to which CAI manufacturers like to make it out to be versus reality are often two very different things).
• If the Ram Air system you mentioned did away with the snorkel which pulls air from in front of the heat exchangers (assuming the Miata is/was built with such a device), then buying or fashioning a heat shield is definitely recommended; without one your Ram Air system may actually be feeding the engine with warmer air than the stock airbox. Go figure.

I hope this helps.

 

Thank you for taking the time to write all of the great info. I suppose from a company stand point it wouldn't make much sense for a CAI company to say "hey, buy our $250 product because we can get you about 3HP more than stock"

I know you don't get a lot of HP, i do however enjoy the sound of the engine, especially when matched to a nice Magnaflow CAT back system. Which the Mazda 6S has already and the Miata will have hopefully in the near future.

And it sounds like getting a heat shield for the Miata may be a good idea just in case

Thanks again. Some terms may be beyond me technically but i get it all in theory which helps too.

 

Any time.

 

the thing that really sucks the gerkin about the CAI is that i bought the best aem i could get, cost around five hundge and the the only check engine light i continuossly set is for the mass air flow sensor since it mounts right in the tube about 8 inches above the cone filter which intern leads to moisture making it through the cone filter up the tube and in contact with the sensor. if it gets too wet it will cause the car to run like complete **** until it dries the sensor wire. i mean the car runs diareah, if you hit 5000 rpms a bunch of lights will come on the dash right before the shift point and it can even cause the trans to mis shift. so when it comes to the CAI watch your ***, and your *****.

 

...or just cut your losses and put the factory intake back on.

 

Well, I got the AEM intake and it ran great. However, it caused my check engine light to go on. I could not figure out how to get it off. I then bought the K&N intake. The K&N intake was easier to install, however, the AEM may have had a very slight performance advantage. The K&N is very user friendly, so if you are mechanical inclined, I would go with the K&N. No problems for three years. Slight MPG increase and a small improvement in throttle response.

 

Oye, here we go again. Folks, a CAI cannot in any way shape or form cause an engine to deliver better fuel economy. Not physically possible.

As for better throttle response, clearly it is a subjective thing, but unless one is referring to throttle response when the engine is north of say 5,000 RPMs, that one isn't even remotely likely either.

 

i put the CAI on mostly for the sound quality because its hard to get a v6 to sound how i want it to without one, and i have no doubts that shipos information is all true but i also happen to know that my intake did increase my horsepower and especially my top end response. i did however lose a little low end torque but when i program my chip a little better ill get it back. it wasnt all bad losing that low end torque cause now when i take my car to the track i dont waste a half second chirping the tires from the start. plus the car sounds F N cool as **** now. it did screw up my gas mileage slighly to but its worth it to me.