Do you know if the high pressure zone at the outer bend in the upper hose acts as a restriction based on your experience in the ventalation work?
I think it does which is the motivation for trying it in the upper hose.
Here is the long winded answer....
All elbows have pressure loss. Duct designers had a list of "factors" to estimate pressure loss in a system. For corragated hose we doubled the pressure loss over a smooth elbow. Today, we have software that use the factors we had back with sliderules.
The air exiting the 1st, corregated, 90 is the most tubulent. The air then slows through the silencer and provides more volume to lesson the pulses of an turbo and engine. This tube straightening vanes smooth out the turbulance.
IF the duct is the same diameter, we use 6 duct diameters, 3" x 6 = 18" to allow the air to straighten before entering the blower. In our case, we have straighening vanes and a larger diameter duct/tube. I suspect the air flowing almost ideal before it enters the last elbow with turning vanes.
ADD to the mix, the turbo is pulsing, each blade pulses. The engine is pulsing, each intake cycle an inrush of air or pulse. AND the volume of air is changing constantly as we speed up, slow down, build boost and many other factors.
We don't see turning vanes in many applications because of the expense and added pressure drop.
Hey, you might find that turning vanes help our intake. You have the parts. We won't know until you run the test!
To protect workers in industriy, the government funded basic research and published information we us to design ventalation systems. These principles applyt to our CTDs.
Here is a link.
OSHA Technical Manual (OTM) - Section III: Chapter 3 | Occupational Safety and Health Administration
And one more if the first one didn't put you to sleep.
Air Ducts - Friction Loss Diagram