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Jabiru Aircraft
Pty Ltd
Installation Manual
Jabiru 3300 Aircraft Engine
REVISION
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Dated : 1
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Dec 2016
Page: 28 of 56
WARNING
When using auto fuels, the fuel delivery system must be designed to prevent fuel vaporization.
To check pressure, insert a ‘T’ piece between the mechanical pump & carburettor. Test boost pump
with engine off, then mechanical fuel pump with engine on, then combine with electrical boost pump as
well, before first flight.
A method for performing a fuel flow test is available from Jabiru if required. In brief, the fuel line is
disconnected from the carburettor, fuel is pumped into a calibrated container and the rate at which the fuel is
pumped (or drained, for gravity-fed systems without a pump) is calculated.
Most regulations require that the fuel system (including pumps) supplying the engine be capable of
delivering 1.25 to 1.5 times the maximum flow rate required for the engine. For a Jabiru 3300 engine this
equates to approximately 44 to 53 Litres per hour (see Section 1.5.3 ). The electric boost pump used on
Jabiru Aircraft generally manages a flow rate of approximately 60 litres per hour.
The Bing carburettor has a
Balance tube (also known as a “sense tube”) which connects the carburettor to
the air box. The tube runs from a nipple on the carburettor to the airspac
e in the air box on the “clean” side
of the air filter.
This tube is part of a system or ports which “tells” the carburettor how hard the engine is
working and controls how the carburettor varies the fuel / air mixture delivered to the engine. Tuning issues
and poor running will result if this tube is blocked or connected to the wrong spot. Figure 30 shows the tube
installation. Note that the balance tube must not be connected to the air box in a location where the air is
moving fast
– rapid flows produces pressure changes and boundary layer effects which mean the balance
tube gives the carburettor “bad” information, which can cause poor mixture control and running issues.
A drip deflector to deflect overflowing fuel from the exhaust system is supplied as standard equipment on the
engine.
Because idle adjustments cannot accurately be made on the dynamometer (where every engine is run
before delivery), some adjustment of the 7mm idle set screw may be required. A hot idle of around 900RPM
is desirable.
Fitting an earth strap from carby to crankcase is recommended to eliminate possible radio interference.
Figure 29. Carburettor Installation
Balance tube
Idle screw
Fuel bowl clip
Fuel bowl
Vent tube from
mechanical fuel pump
Drip deflector