Many thanks for your quick response guys. That is what I vaguely suspected: the air is not drawn from the front but from the engine compartment itself.
But:
1. why on earth the IBF in my original pics is located in front of of the transmission cowling? Obviously, its function is to filter engine air. (There is another version of the IBF, it is a big screen located on the engine compartment which supports our concept.)
2. As I learned, the grill on the xmission cowl is the oil cooler outlet, the vent behind the cabin window is for electrics. (See the pic. of the black/white heli.) What left is two small NACA scoops on the top and a rather small grill on the engine cowl. ..and this is for a powerfull engine. Strange!
The model picture is interesting. The silver housing around the engine is the intake box (by my limited knowledge). It has to have an opening somwhere on it. I can't see it from this angle, maybe on the bottom?
Cheers,
Tamas