RAM Air or Cold Air

[TheStig]

What the heck is the difference between RAM Air and a Cold Air Intake???? I mean I know that Cold Air involves a cone....but still....any difference really????

[1.2gees]

RAM air implies that the force of the air flowing around the car is forced into the intake route. A slight supercharger if you will.

A cold air intake simply draws air from a cold location (wheelwells usually, or right behind from bumper, most likely the tubes go down low, where air will be theoretically colder).

Ofcourse all RAM air systems by definiton get their air from outside the engine comp. and in effect are cold air intake systems.
Ahmet

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It's all the driver...

[TheStig]

Would RAM Air work on a 928 if 2 holes were cut in its hood allowing air to get into the intake pipes via the modified hood? My uncle did this update on my dad's 1985 928S which he now owns, I'm not sure how much HP he's gettin now...but the last time i checked, with all his mods and a little help from devek, somewhere around 543 HP.

[1.2gees]

Only a way for air to get in the engine comp. wouldn't make it a ram air induction.

Ram air is when the air is directed toward, and pushed into the intake tracts...
Ahmet

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It's all the driver...

[Lawrence Coppari]

Best way to think about ram air would be to imagine an engine sitting on a workbench so it is stationary. In order to get air in the engine, the air around the engine pushes in due to the low pressure inside the engine when the piston is down on the intake stroke with the intake valve open. The amount of air that enters the cylinder is based on the difference betwee outside atmospheric pressure and internal cylinder pressure. Because outside pressure is greater than the air pressure in the cylinder, air rushes in. The amount of air that gets in depends on the pressure differential between inside and outside. That pressure differential gets consumed by the acceleration of the air (You don't get something for nothing in this world). For a given pressure differential (and pipe size) only so much air can enter because the air must accelerate from zero velocity. Now, if you blow a fan at the front of the air intake, the air already has some velocity, and the pressure differential is used up accelerating the air from a velocity greater than zero. Therefore more enters the cylinder.

Superchargers and turbochargers increase the external pressure (bigger pressure differential) which causes more air to enter the cylinder; hence, more power is made because you can then dump more fuel in.

A cooler air charge means the density of the air is greater. That means more air and more oxygen. Therefore more fuel, ergo, more power.

[AMCPorsche924Powerhaus!]

Cooler air also simply helps lower preignition problems since too much heat is bad before the spark occurs.

Ram air on some cars (most?) has very little affect for HP, but it helps reliabilty and economy. The effect of ram air is much much less than a turbo or supercharger, because ram air only really helps at highway speeds, it isn't going to help you acceleration unless your at maybe 60 clicks adn want to go to 80? Or at least thats what i think would happen with ram air, i don't speak from experience yet.