Wren 44 TurboProp Users Manual. Copyright Wren Turbines Ltd February 2008 Page 21
Care should be exercised to ensure that no foreign object, loose parts of model, or debris is
allowed to enter the compartment where the engine is installed.
If required, it is approved to extend the rpm and exhaust thermocouple wires using a high quality
gold plated servo extension. Such plug/socket extensions should be secured with heatshrink or a
cotton tie to ensure they cannot pull apart.
Fuel.
Only use paraffin / kerosene or Jet-A or an approved equivalent fuel. This fuel should be filtered
at each stage of mixing and transfer to model fuel tank. The pickup filter (provided) must be fitted
to the fuel tank. This should be maintained to ensure correct operation.
A final fuel filter is pre-fitted to the engine in the fuel line just before the green cover. To
disconnect the fuel line from the engine, disconnect at the quick release connector at fuel filter.
Lubrication Oil.
This fuel requires an approved lubrication oil mixed at the rate of
5% oil
to
95% fuel
. Note this is
more than is normally recommended for Wren engines as it also has to provide lubrication to the
gearbox. Using a lower oil percentage than this can cause early failure of the gearbox and/or
bearings.
If fuel is already mixed to the previous 2.5% then simply add a similar additional quantity of oil to
increase to the 5% required. All Wren engines can run with 5% oil without harm if you want to
keep just one mix for all your engines.
All pipe-work used must be of the type supplied by Wren Turbines.
Fire Extinguisher
Equip yourself with an appropriate fire fighting extinguisher whenever you are planning to run
your engine. The best extinguisher for our purposes is the Carbon Dioxide (CO
2
). Use of dry
powder, foam or water based extinguishers will cause serious damage to the engine and should
only be used as a last resort.
DON’Ts.
Never mount the engine using woodscrews – it is impossible to ensure they cannot loosen or pull
through from the firewall.
Do not use second hand fuel tube – it can harden with use and not allow a proper seal. Silicone
tube must never be used anywhere in the installation as it is dissolved by the fuel and oil.
The engine must never be run with the gas pipe open to atmosphere.
Do not install filters in the feed (suction) line from the fuel tank to the fuel pump. This is known to
cause aeration of the fuel and flow disturbances resulting in stoppages.
Do not use fuel which has not been properly filtered. Dirty or contaminated fuel can result in
blockages of the fine fuel injectors in the engine or blockage of the engine lubrication system and
subsequent bearing damage.
Never break the fuel line after the filter as this can allow debris to enter the engine fuel system
which can cause severe damage to bearings and combustion system.
Do not extend the rpm pickup or temp probe wires by cutting and soldering in extra lengths, as
this renders them non-standard and historically has been a regular source of failures.
