1.2.2
Airflow to the Engine
The engine has to be installed in such a way that the fresh air stream supplied is sufficient to
insure its cooling and adequate for the supply of air to the carburettor.
For a cowled installation it is necessary to take care that the outgoing hot cool air stream is
not allowed into the carburettors, since that will lead to a drastic reduction in performance. At
the same time, the outgoing hot cool air stream must be able to exit the cowling without
blockage, since this will force the engine to overheat and lead to its destruction.
The engine's forced air-cooling system is designed so that if enough fresh air flows in, the
satisfactory cooling of the engine is insured in any type of operation. No changes may be
made in the cooling system.
It is absolutely imperative to have a sufficient supply of fresh air.
1.2.3
Fuel System Layout
The fuel supply of the engine is supported by a diaphragm pump (Illus. 1.2.3-1), operated by
pressure from the crankcase.
Illustration 1.2.3-1
(Diaphragm Fuel Pump)
This fuel pump is situated in the fuel line between the fuel tank and carburettor. A fuel filter
should always be installed between the diaphragm pump and fuel tank. The diaphragm pump
should be installed at a place with the least influence of vibration or heat.
Take care to insure that, with an upright installation of the diaphragm pump, the fuel exit is on
top. The placement of the connecting pieces can be recognized by arrows on the casing.
The central connection of the fuel pump is the impulse connector. The impulse line from the
crankcase to the diaphragm pump should be as short as possible, straight and inclining toward
the diaphragm pump. When choosing the impulse line and the fuel line, take care to use rigid
lines, which do not expand under pressure. The impulse line should not exceed a maximum
length of 150 mm and a minimum inside radius of 6 mm.
In any case it is advantageous to position the fuel tank above the engine, since this ensures a
certain pressure to the fuel supply. In addition, however, it is recommended to use the
diaphragm fuel pump. The fuel pressure should be checked with an appropriate measuring
instrument in any event.
When installing the fuel tank underneath the engine, the following geometric data must be
noted.
The maximum length of the suction line between fuel tank and membrane line should not
exceed 2000 mm with a minimum inside radius of 6 mm. The maximum suction height must
Impuls connection