NAVMAN
8120/8084
Installation and Operation Manual
53
13-6 Fuel consumption curves
A fuel consumption curve shows fuel
consumption (fuel used per unit of distance
travelled) and boat speed as a function
of engine RPM. Fuel consumption curves
require engine RPM, which requires
SmartCraft or diesel sensors to be installed.
Fuel consumption curves are powerful tools
for assessing boat performance in different
conditions and for helping you to run at the
most economical speed for the conditions.
13-6-1 Making a fuel consumption curve
To make a fuel consumption curve you will
need to run the boat in a straight line for
about 15 minutes using the engine’s full RPM
range. For your first curve, choose a calm
day with light wind and little current; have a
typical load and a freshly cleaned hull. Later,
you can make fuel consumption curves for
different boat, weather or sea conditions.
Compare these with your first curve to see
how your boat’s performance changes with
conditions.
Making a curve
1 Start running the boat in a straight line.
2 Choose a speed source for the curve (see
section 13-5-1). Normally choose Water
speed to measure the boat’s potential
performance.
3 Press
MENU
twice, then select
Fuel
.
4 Select
Fuel consumption curve
,
then select
New
.
5 Enter the comfortable maximum RPM
you know you can achieve for the engine
rather than the maker’s value.
6 The 8120/8084 then asks you to set the
minimum RPM. Set the throttle to idle;
on a multi engine boat set all engines to
about the same idle RPM.
Now, do not change the engine speed.
Wait for about 60 seconds for the boat to
stabilise, then press
ENTER
. Wait while the
fuel computer records the data.
7 The 8120/8084 then asks you to set the
throttle to achieve a target RPM. On a
multi engine boat set all engines to about
the target RPM. When the engine RPMs
are correct, the Target RPM box will turn
green.
Now, do not change the engine speed.
Wait for about 60 seconds for the boat
to stabilise, ensuring the Target RPM box
stays green. Then press
ENTER
. Wait while
the fuel computer records the data.
8 The 8120/8084 repeats the above step
to record data up to the maximum RPM.
Then the 8120/8084 asks if you want
to save the curve. Select Yes. The fuel
computer asks for a name for the curve.
Change the default name if required. Then
press
ENTER
. The 8120/8084 stores the new
curve.
Note
To interrupt making the curve at any
time, press
ENTER
.
