SDS EM-5-D - Closed Loop and Fuel Cutoff Limits

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Both START and START CYCLES must be set carefully. If the engine fires immediately at any
temperature, the START values are good. If the engine takes a lot of cranking to get running, the
START values may be too low. If the engines starts quickly but then stalls after a few seconds, there
are two possibilities; either the START CYCLES value is too low or when the start cycles have
expired, the ENGINE TEMPERATURE values are too low. Once the start injection cycles have
occurred (usually 3-10 seconds), the EM-5 relies on ENGINE TEMPERATURE values for warmup
enrichment. These two parameters should not be confused. The START function is automatically
reset after the engine stops turning.
Closed Loop
Generally in aviation applications, we do not use the closed loop function as this targets stoichiometric
mixture which equates to peak EGT. We recommend you leave closed loop turned off at all times.
Fuel Cutoff, Rev and MAP Limiting
RPM and MAP limiting in SDS are very harsh so it is not recommended that you constantly hit the rev
and MAP limits with SDS. These limits are intended for protection only, primarily for propeller
governor or blade loss conditions. Set them slightly higher than your maximum limits so you don’t run
into them in normal operation.
Fuel Cut /RPM
This will limit the RPM’s of the engine by cutting off fuel if the engine attempts to rev higher than the
setting. For example if the FUELCUT/RPM was set to 3000, then fuel would cut off at 3050 or 3125
RPM’s depending on rpm steps in your programmer. Adjustments are in 100 or 250 RPM increments.
Fuel Cut/ MAP
Generally only used on forced induction engines. This will limit the amount of manifold pressure to
protect the engine from over-boosting resulting from a malfunctioning wastegate etc by cutting off fuel
injections when manifold pressure exceeds this setting. For example, if you are running around 40
inches MAP you should set this parameter to around 42 or 43 inches, so the engine will not hit the
limit under normal conditions.
Factory setting is NO CUT which disables this feature, so it will not affect the system. If this
parameter is adjusted to a low MAP range, it can cut off all fuel causing a no start condition.
Fuel Cut/ Below TP
This parameter is used to cut off fuel when gliding with the throttle closed. It is in operation only when
the engine is above 2000 rpm and a TP value is entered in the window. When it is set to NO CUT the
function is disabled. This parameter is usually not used in aviation applications.
RPM Switch
This feature is usually used on Honda VTEC engines to to control the VTEC solenoid.