Design Improvements for the Zenith 601 HDS:
The radiator is mounted on the right hand side of the engine.
The cooling air is forced into a cowl opening and then expands
in an aluminum housing ahead of the radiator. This increases
the air pressure in front of the radiator.
Despite its small size, the radiator has
ample cooling capacity. Total coolant quantity is
an amazingly small 2 1/2 quarts. The system has no thermostat,
yet operates always in the appropriate temperature range since
low engine loads correspond to low propeller rpm and thus
to low volume of cooling air. A critical feature is a bottom
lip of the engine cowl that permits the air to exit into the
slipstream. For the development of testing of the configuration,
air pressures were measured in inches of water column, using
a straightforward U-tube for the measurements.
Below, the green discoloration visible on a small portion of the
radiator was produced by an initial radiator leak that was easily fixed.