Vega EMS-1 Operating Manual
Page 58
11.6 Fuel flow sender installation
The fuel flow sender allows the EMS-1 to provide instantaneous readout of hourly fuel usage.
Please note that the installation of the fuel Flow sender should be done in such a fashion that dirt or debris from
the fuel tank cannot lodge inside the flow sender. These will not block you fuel flow but may lead to the impeller
inside the sender jamming. It is usually sufficient to mount the flow sender AFTER the fuel filter but before the
fuel pump. It is a good idea to provide a small reservoir such as a primer bulb between the flow sender and the
fuel pump.
As indicated in the recommended installation drawing, it can be of advantage to install the flow sender in such a fashion
that the inlet points slightly down and the outlet points slightly up. This prevents vapor from forming a bubble inside the
flow sender. We strongly recommend mounting the flow sender in such a fashion that the impeller rests on only one
bearing. This is achieved if you mount the sender such that the surface with the arrow faces upwards. Mounting the
sender like this results in the best performance at low flow rates as only very little friction is present. The flow sender is
delivered with a small jet that can be installed in the flow sender inlet. Installation of this jet is recommended for engines
with fuel flow rates lower than about 30 Litres per hour. This would apply to most small two and four stroke engines. The
EMS-1 is shipped with the fuel flow sender calibration set for the jet installed. In a good installation you can expect about
+/- 3% maximum flow reading error with this factor. You can calibrate the flow sender yourself to a higher degree of
accuracy if you so desire.
Recommended procedure to calibrate the fuel flow sender:
Note:
You must disable the fuel level sender if you have one installed, and enable the calculated fuel level sender.
1. Fill your tank exactly to a known level (for example 50 Litres).
2. Set your fuel level to 50 Litres.
3. Fly your aircraft for a period that you know will use approximately 20 Litres of fuel. The exact fuel burn is not
important; just burn about 20 Litres of your fuel. At the end of your flight the instrument should give you a reading
of how much fuel you have left – the reading should be about 30 Litres left.
4. Now place your aircraft in exactly the same position that you used when you first filled the tank and refill the tank
to 50 Litres using a measuring jug. You should find that you need 20 Litres of fuel to refill to 50 Litres.
5. If you find that the instrument under or over reads the fuel used, you should perform a simple adjustment of the
fuel flow sender calibration factor.
Example:
Actual fuel used: 21.5 Litres, FF-5 fuel burn calculated 29.7 Litres left in the tank. This means the EMS-1 measured 50-
29.7 = 20.3 Litres. We are under reading by 1.2 Litres.
Default calibration factor in Fuel setup menu = 7000.
Let the corrected calibration factor be X.
X = (20.3 * 7000) / 21.5
X = 6609.3
The closest setting you can enter as factor is 6609. Enter it into the unit and you are done!
Repeat the above procedure to verify that your flow sender is now reading correctly.
Please note:
Before you calibrate the flow sender ensure there are no problems with your installation. We find the senders are very
accurate if everything is installed and working properly. If your fuel burn indication is out by a large amount you have a
problem that you should not attempt to fix by fiddling with the calibration factor! Please ensure that no fuel vapor can be
trapped inside the sender housing in the form of bubbles. Due to the low fuel flow rates the bubbles will prevent the tiny
impeller from turning freely, you can verify the turning of the impeller. You should notice three dark spots that are just
visible in the inside of the fuel flow sender. These are small magnets that are attached to the impeller. With fuel flowing
you should see the magnets turning. The best defense against vapor bubbles is to install the flow sender in such a way
that the bubbles can escape. The easiest way is to point the outlet slightly upwards and the inlet (with the jet) slightly
