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Engine Control
The fuel for the engine is provided from a fuel tank and fed through a small pump driven by a 3-phase
(brushless) motor that has its own intelligent control. The engine speed between idle and maximum is
controlled by varying the speed of the fuel pump rotor by command from the electronic device called an
ECU (Electronic Control Unit) that is mounted under the front cover of the engine.
This sends commands to the fuel pump via a connector board (Hub) to turn at a certain rpm (and
therefore flow rate) to deliver a precise amount of fuel and the fuel pump automatically adjusts itself to
this rate.
The communication between the ECU and fuel pump and all other function accessories, display,
telemetry etc is via a single wire bidirectional digital data link, no analogue voltages are used and
operation is not voltage sensitive as long as sufficient voltage is maintained for digital signals to be read.
To control the admission of fuel to the burner and main combustion chamber there are two miniature
electric valves attached to the front of the engine under the cover and also the 4mm quick-release fuel
feed connection. The valves are connected to and controlled by the ECU as required by the starting
sequence. The valve assembly is replaceable but the individual valve assemblies are not user
serviceable. The main fuel connector is marked "F".
The 2
nd
4mm fuel feed connector is the fuel/air connector to gearbox and should already have the lube
pipe installed. It is marked with an "L".
PLEASE NOTE: This is NOT interchangeable with the main fuel
connection, so do not swap
them.
Component Description
ECU (Engine Control Unit)
The ECU and indeed the whole system used on this engine is totally new and unlike any previous
version of Xicoy ECU. The ECU is a powerful new design using a completely new architecture so
represents not an upgraded version of anything before but a new system completely. This new platform
allows us to break from the limitations of older technologies to make use of the latest high speed
connectivity to add many more functions than were possible before, and all using a single wire data
cable. The heart of the ECU is one of the latest high speed microprocessors which enables it to carry out
millions of instructions per second and do a great many things at the same time without having to stop
and wait. It has its own memory so can hold programme instructions and operating data and store
runtime data from previous engine runs.
The new controller is in the form of a small C-shaped circuit board fitted under the front cover of the
engine. It directly controls the two fuel valves, the brushless starter motor and internal glowplug. Two of
the three wires in the 3-cable are the power for these. It is connected via the 3-wire cable which plugs
into the engine and a small connector board called the "Hub" externally (also available with built in
display called the "Compact Hub"). The Hub acts as a clearing house for ECU data and the outside
world. The three wires are just plus (+) minus (–) and data. The signals in and out of the ECU are via
bidirectional digital data link, no analogue connection to the outside world is required, or possible.
Flight data can be stored by using a regular micro SD card plugged into the small colour display
mounted in the aircraft to store many additional hours of operation which can be reviewed using a simple
PC viewer.
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