All about hot air...

[Project84]

Originally Posted by theholycow

I agree that at WOT cold air with produce more power, but why would it use less fuel per horsepower?

Because horsepower and fuel consumption aren't ALWAYS linear. Sometimes while dyno tuning people find that removing fuel actually increases horsepower substantially.

More AIR = more power... hence turbocharging. Yes this generally requires more fuel too, but not enough to cancel out.

[koji_kabuto]

less fuel per hp on cold temp? beats the purpose of wai/hai plus temp only determines the density of air.

map and maf.. a lot of misconception here guys.

both uses correction factor, theres air temp sensor, barometric sensor, oxygen,tps... almost all engine management systems can use both sensor, its just a matter of voltage offset to run them properly.merely preferrence if you were going to choose either one with manufacturers, GM didnt use ait at some point because they were using resistive wire for their maf, with that they can calculate temp along with tps but not accurately. now almost everyone incorporated maf with ait in the same sensor. thats less parts to buy and less man hours to manufacture and install. with map sensor you cant have both in the same package because ait must not be inside the intake manifold, we all know as the pressure drops when tb is closed the temp also drops.

[IndyFetch]

I installed a K & N Typhoon intake on my 2008 Civic Si. It still has a tube connecting it to the cold air supply, but it is no longer sealed in a box. Therefore, the intake has access to the hot air under the (packed) engine bay. Prior to installation, my intake air usually did not crack 90 degrees. Now it averages 110, and I have seen it jump to 145 while sitting at a red light in 90+ degree weather without the engine running (hence, no fan).

Prior to installation of the intake, I had 2 tanks at 32-33 mpg. After the installation, I am averaging 36 mpg, and as high as 38 in mixed driving. Not bad for a car that is rated as 29 mpg highway and 25 mpg combined. I do not P&G much; I'd get run over. I drive 55 - 65 mph on my commute, and draft when I can. I attribute the gain in mpg almost solely to the warmer intake air.

[Sludgy]

Originally Posted by theholycow

I agree that at WOT cold air with produce more power, but why would it use less fuel per horsepower?

At least one reason is that engine friction is not directly proportional to power output. For example, friction (drag) due to oil viscosity is independent of power. There are other factors too, such as water and oil pumping that are somewhat independent.