Cowl Inlet Shape Difference

[bjdecker]

For the Van's folks and others who may be "in the know" - why is the cowl inlet shape on the horizontal fuel injected cowl for the RV-7 different than the RV-8?

Pictures of both attached -- the white cowl inlet is from the -8, the blue is from the -7.

FWIW, the RV-14 cowl inlet shape is closer to the -8 version -- top and bottom front edges are parallel.

 

[Ralph Inkster]

Maybe the older molds were hand formed versus cad designed. Maybe one designer liked the slanted look versus the later design.
Different plenum depths may allow larger inlets in the 8 & 14.
I don’t think there is any more complicated reasoning behind the newer inlet shapes.

 

[wirejock]

Inlets

Maybe the older molds were hand formed versus cad designed. Maybe one designer liked the slanted look versus the later design.
Different plenum depths may allow larger inlets in the 8 & 14.
I don’t think there is any more complicated reasoning behind the newer inlet shapes.

Or the builder could be a bit OCD

 

[BruceW]

(minor thread drift)
I recall reading about inlet shapes years ago. Dont recall anything on the actual shape of the inlet making a difference. Of course total area of the inlet is important.
There are other parts of the inlet that effect efficiency and internal cowl pressure.
- Radius of the edge curve. Apparently a sharp edge is not as efficient. There is a sweet spot somewhere.
- Spinner to inlet transition. Dont recall the details but it makes a difference.
- Distance from inlet to back of prop. Closer = generally more pressure.

I am assuming that Vans has tested this all out and has concluded the best fit.
Its all a balance of multiple factors.