Quote:
Originally Posted by Laird Scooby
Pretty much it in a nutshell Rob. 
Also when the fan is stationary, the shroud creates a bit of venturi effect around the actual fan area, increasing the speed of the air flowing through it from forward movement of the car.
Again this helps to get a good volume of air through, even without the fan running. |
The shroud is only for stationary low speed effect to ensure air comes through the radiator rather than from beside it. Its is actually a disadvantage at vehicle speeds above the fan air movement speed, and blocks air flow. Removing the shroud was the biggest improvment I got in my overheating 360 turbo on summer track days. Although it has no speed relief valves as apparent in the pics.
The air may well speed though the fan when the vehicle is moving but that doesn't help anyone. It will be overall slower through the rad because of the shroud. Its is rad air speed that is important. I think the shroud also increase air resistance of the car.
Mostly in this country you can get away without a shroud for non-AC cars.-