The ram effect

[beanjay]

Hi, I'm new here so would like to wish everyone well!

I'm looking for some information that I once had but is now long forgotten.

Sixty years ago I was studying motor vehicle engineering and we had an engine in a test bed that we supercharged with no mechanical devices that had moving parts.

All we did was to place a very long tube over the carburettor intake. The tube was long and straight and smooth on the inside. The theory was that the air being drawn into the engine would achieve a ram effect due to its increased speed inside the tube before it reached the carburettor.

There was just one piece of magic! The length of the tube was calculated using a formula based on the diameter of the tube and this appeared to be critical.

My problem is that I have forgotten what that formula was and I was hoping someone could help me with that?

I would be very grateful because I want to use the principle on another project I am working on.

Many thanks

Bob