Laminar flow is smooth, non-turbulent flow all going in the same direction. Turbulent flow is chaotic flow, all kinds of random flow directions. Think of it like cattle. You have herd that you're moving from one field to another. Across the open field they all move in the same direction as you're directing them. That is laminar flow. Except those out at the edges, they tend to peel off and try to do their own thing. That is the boundary layer.
Once you get to the gate those inline with the gate go thru it, but those around the edges mill about, turn the wrong direction, and generally make more work for you. That is turbulent flow. Notice how those milling around tend to make the gate opening narrower than it actually is. That is why predominately turbulent flow in the ports isn't desirable.
Even air has friction, both to itself and to other things. So a rough surface will cause it to 'stick' more than a smooth surface. That results in what is called the boundary layer. It is easy to mentally picture this in a cross section of the port, but remember that it exists anywhere that there is port wall. Can think of the boundary layer being like the skin on a sausage, only depending on both the velocity of the 'meat' and the surface roughness of the port walls it's thickness will vary.
"Ram Air" is a way to slightly increase the atmospheric pressure on the carb. The effect is similar to turbo or supercharging, but at most it is only worth a couple psi at normal road speeds. If one stick of dynamite is good, then 1.5 sticks would be better and 2 sticks would be better yet. Right? That is what is happening here, by forcing more air through the carb and into the engine there is more power to be had in each ignition event. If the throttle is partly closed, like in a cruise condition, then it's effect is lessened but it's there when you might need it.
My Valiant is the second car that I've done a cold air system on. On the first car where I most noticed a difference was on really hot days. The engine ran cooler on those days than it did before I made the ram air parts. It wasn't huge, but it was noticeable.
One thing to be thoughtful of/careful of when building a ram air system is water. Whether it be on the road or in the air, you don't want your system to feed it to the engine. With GM truck cold air intakes they poke it thru the core support up high (so it won't suck in water from a puddle) and then put a baffle in front of the opening that is slightly larger than the opening. The air will make the turns, but the water will mash up against the core support and dribble down it. My first system didn't do a great job of dealing with water and I sometime had soaked air filter elements to prove it. This one on the Valiant has a vertical turn that goes up much higher than the ID of the intake tube so that any water will hit the back wall of the tube and will condense and dribble down to the bottom of the curve where there is a small hole to drain it out.
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