SDS EM-6 - Page 49

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The amount of fuel injected by the EM-5 is determined by the values in rpm fuel, manifold pressure, acc
pump, engine temperature, start, air temperature. Once, the engine is at full operating temperature, the
main values that determine the fuel mixture are RPM FUEL and Manifold Pressure. Most of the Manifold
Pressure values can be left at their factory settings when the RPM FUEL values are set properly. RPM
FUEL values are where programming should begin.
RPM Fuel
The rpm band is divided into 38 ranges, either 100 or 250 rpm apart. This parameter is where the main
fuel programming is done in SDS systems. The variables which ultimately determine the RPM FUEL
values are engine displacement, injector flow rate and volumetric efficiency of the engine. Volumetric
efficiency varies with RPM. As a result, RPM FUEL values will vary accordingly. If a richer mixture is
desired at certain RPM’s, the RPM FUEL value will need to be increased. There should not be large
changes in adjacent values in RPM Fuel, rather smooth transitions.
Example here, the LCD display shows one RPM Fuel window. The RPM range is 1800 and fuel amount
number is 165.
Your system has a base map entered for the recommended injector flow rate or for the injectors included
in your kit.
Often people have their RPM FUEL values incorrect and find themselves having to re-slope the entire 64
manifold pressure values, which can lead to further problems. When the RPM FUEL values are setup
correctly, the majority of manifold pressure values can be left unchanged, thus greatly simplifying tuning
of the engine.
If you double the RPM FUEL value, this will double the pulse width of the injector pulse. If you wanted to
make the mixture 10% richer then you would simply add 10% to the RPM FUEL value. Example: RPM
FUEL value was 100, and is then changed to 110. This would add 10% more fuel to the mixture.
It is important to note that the number of injections are doubled when the rpm is doubled
regardless of the values entered. See figure 4.
The maximum RPM fuel value is 350.
Startup Procedure
Make sure that fuel at the correct pressure is present at the injectors. Turn on ignition and computer
power. Crank the engine, rotate mixture knob richer while cranking. If engine does not fire, see
troubleshooting section. You may also have to increase the START values to get the engine to fire.