Heinz, yes I have seen the video showing airflow. I agree with Dave about the heater box area giving a "positive" pressure.
But...on my Plus8 the air being sucked in is not pressurised but I guess at normal pressure. It is completely underbonnet so airflow around the engine itself is what it gets. My guess is just sucking in the hot air as the exhaust manifold is below the open end of the intake. I doubt if there is any positive pressure under the bonnet.
Just guessing, but I think the engine would suck in air through the louvres , even rear facing ones, if a good seal could be made to the inside bonnet surface.
It would be nice to see a repeat of the airflow test for a roadster to see if the wool threads show strong airflow in through the louvres. Care though not to suck in the wool threads!
