Design Improvements for the Zenith 601 HDS: Cowl Inlets
Cowl Inlets
The photo shows the small horizontal cooling inlet for the engine
and the inlet for the radiator on the right hand side.
No baffles are used to direct the air around the cylinders, without
any noticeable adverse effect so far.
The duct for the radiator cooling air is rather close to the engine,
but does not touch the engine.
The 2-inch NACA inlet for the oil cooler has been modified by an air
scoop. According to tests, the added scoop
apparently has the following desirable
effect. Under low propeller rpm,
the amount of air entering the scoop is reduced. This is desirable, since
otherwise the oil temperature drops too low. With high propeller rpm,
the amount of air is drastically increased.
As a result, even with 94 deg ambient air, a climb out
at gross weight and with airspeed at or above 70
KIAS produces an oil temperature not exceeding 230 deg.
Generally, the airspeed of climb outs is crucial. A climb out at 60 KIAS
even at comparatively low ambient temperatures results
in unacceptably high oil temperatures.
