quoted twogts4us,The air ingested by the engine takes approx 1/10th of one second to go from the air cleaner to the combustion chamber
what scientific data is that based upon
, now think of the engine of a big vacuum cylinder. get a cylinder of some sort, maybe something that has at least a cubic foot air space, (i know you cant fit a round peg in a square hole) put a few drops of water in the bottom, when you pull vacuum the ambient air heats up, any moisture in there will vaporize and disapeare
. now back on point i stated that air moving at a rapid speed will cool down a little bit. now my scientific principle is stand in front of a fan now with it off, turn it on, now turn it off, now turn it on, get a thermometer if you want, and see whats cooler. with it on or with it off?
First, moving air is a very good heat sink. That's why a radiator works. The air moving past the radiator takes with it some of the heat of the radiator. If moving air didn't absorb heat in that manner, radiators would not function.
That's also why you feel colder when standing in front of a fan. You feel cooler because the moving air takes heat away from your body, effectively cooling your skin and making it feel like the air is colder than it is. A thermometer would tell you that the ambient temperature hasn't changed, showing that the cooling effect comes from the moving air.
Second, when you apply a vacuum to a cylinder containing a few drops of water, the water drops will turn to vapor because the ambient pressure is too low for it to remain a liquid. Basically, you've boiled the water off by dropping ambient pressure rather than by increasing temperature. The temp inside the cylinder will actually drop. A gas like air actually increases in temperature when compressed, and decreases temperature when pressure drops. Anyone with a supercharger can testify to this.
A hot intake will heat the incoming air. And it's not just the air that contacts the sides of the intake that will absorb heat. The hot intake radiates heat. You can tell something is hot just by placing your hand near it. The air moving through an intake absorbs heat this way. Air doesn't have much mass, so it doesn't take very long for it to increase in temperature. Think how long it takes to heat an oven to 350 degrees vs. boil a large pan of water.
The issue with a metal intake is that the mass of material absorbs heat energy and conducts it very well. The more mass, the more heat it will absorb. A composite intake has very little mass compared to an aluminum unit, so it doesn't take much air moving through it to drop its temp to very close to the incoming air temp.
The more conductive a material, the faster the entire unit will reach the same temperature as the hottest location. For example, the heat from the heads is transmitted throughout the whole intake much faster when it is constructed of aluminum than when the intake is a composite material that conducts heat poorly. This means that the aluminum intake will absorb more heat faster than the composite piece. And since it has absorbed more energy it will take more air moving through it to cool it. The result is that no matter how much or little heat you think incoming air will absorb, an aluminum intake will heat more air.
Heat kills power. Hot air is less dense so it contains less oxygen by volume. Which means less fuel can be burnt, and the amount of fuel burned controls how much power is made. Hotter air -> less O2 -> less burned fuel -> less power.
Composite intakes absorb less heat and conduct heat poorly, so pass on less of the heat of the engine to the incoming air charge, resulting in a denser mass of air in the combustion chamber, and therefore make more power.