My only concern with that is if you could get 1 to 1 1/2 lbs of free boost with a properly designed scoop then that would be 1 to 1 1/2 lbs less boost that the turbo would have to supply
Sum, sadly it doesn't work that way. I can't find the darn reference, but this was from a previous post (the link to the reference was broken)
As you can see maximum theoretical ram pressure (incompressible flow) at 200 mph is 102.326 lbs/ft^2 or about 0.71 psi.
You would like to think that if you put up a scoop the size of a billboard you would get huge pressure. At the speed we run the air is relatively incompressible and partial pressure is the best case.
You could have a hole or airflow that restricts flow. On a turbo that may or may not affect horsepower. If you can still achieve maximum boost that the engine will take with a reduced inlet, then no problem.
On the other end is too much air. Then drag becomes a factor.
In between the two is what you are looking for. The scoop size can be incredibly small if it is sized for speed. The engine will be to some extent starved at lower speeds. If you calculate the size for various speeds you will see that what you really need is a stretchy inlet! Panic is correct that a bleed inlet is helpful to avoid restricting the inlet at low speed.
Jon, I would look to get the inlet out the front to get the cleanest air that you can. If you can't, then a pressure sensor at the inlet will help tell you determine what the pressure looks like during the entire run. On the dyno you would see constant negative pressure because there isn't any mechanism to push air towards the inlet. It might be possible you can pull in enough air without going out into the air stream.
Omega Engineering PX26-001GV Sells a $35 0-1 psi pressure sensor.
At speed you have the advantage of using the high pressure areas to push the air into the turbo. Not only aids the turbo, but the aero too by reducing the pressure in that area.
The shape of the scoop on a car is almost always an opening above the body to get into the clean air away from the turbulence. It doesn't have to be. Some of the cars have intakes out the front.
A
properly designed NACA duct is designed to pull air from the body with the least amount of drag. Location is all important. I believe a scoop will give better performance.
Sum mentioned pulling air from the front "if I could figure out how to smoothly duct the air from there down to the turbo inlet in a progressively larger duct." The need to go progressively larger isn't as important as calculating conductance losses through the path. There are formulas for calculating flow through pipes that work here. Drag on the body and inside a pipe are the same. You can go progressively larger but I doubt it would gain much. Just make sure there aren't restrictions in the path. Dumping into a huge plenum is as effective as trying to calculate a resistance free path.
