Plastic dirt/splash panel under Engine

[poison]

Not sure what it's really called but it's the large plastic panel that sits
below the engine, I assume it's to keep out dirt and water. I've had mine off
for a month or so (since my cam belt) and wondered if there is any issue with
having it off. Old cars never had them and surely the car engine bay must be
cooler with more air flow. I am guessing that there would be a low pressure
under the car which will allow more air thought the radiator. With the engine
bay all closed up it must pressurise to an extent reducing the airflow through
the radiator. Obviously the Mazda engineers did all the maths but I just
wondered if it really is just a dirt/splash panel. Anyone know?

Gazza
"PO1SON"