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The more open the throttle is, the higher the manifold pressure, so the manifold pressure values must be
larger. SDS delivers a longer injection pulse to put more fuel into the cylinder. By adjusting the manifold
pressure values from their default, you can change the mixture of the engine at different MAP to achieve
best power or economy.
Use Gauge 1 mode to see what manifold pressure range the engine is running in, then use the < > keys
on the programmer to move to the range you want by adjusting the values if desired.
Lean Warning
For aircraft in most cases leave this Disabled. Requires a wideband O2 kit and unleaded fuel!
This feature allows some protection against a lean condition at higher throttle openings. You must have a
wideband meter that has an analog output connected to the SDS main harness gray wire and a TPS
installed for this feature to operate. This feature may not be reliable with leaded fuels since they affect
operation of O2 sensors. If enabled, the system will monitor the O2 sensor voltage, and when throttle
position is 35 or higher, and if the mixture is leaner than approximately 14 to 1 for 2 seconds, then an
ERR message will be displayed in Gauge 3 and Gauge 4 modes in place of A/F or O2 volts. Also this will
turn on the check engine light output on the ecu. The ERR message and check light remain until you
manually clear them by pressing +10 while in Gauge1 mode. The ERR message and check light also
clear when SDS is powered down.
There are 3 settings for this parameter:
1. Disabled. Correct setting when no O2 sensor is connected to the SDS ecu.
2. Enabled. Turns on Check light, and displays ERR in Gauge modes. Does not add fuel.
3. Enabled + add fuel. This does the same as the Enabled setting, plus when the ERR occurs, 25% will
be added to the fuel mixture above throttle position 35. This may help prevent engine damage by
allowing the tuner time to acknowledge the problem and close the throttle. To clear the ERR
message press +10 while in Gauge1 mode, then this will remove the extra 25% fuel. Then further
tuning or troubleshooting should be done.
We recommend that lean warning be disabled on engines which will routinely be running lean of
peak (LOP).
Lean Warning should be set to Disabled when there is no TPS installed.
Lean Warning may not function long term when Leaded fuel is used since the lead may foul the
O2 sensor. Lean warning will not function unless a TPS is used.
The Lean Warning will not function if O2 Type setting is “NONE”.
Idle
It’s best to adjust RPM FUEL values first to get the best idle mixture. If you have a wideband meter, a
good target mixture for idle is 12 to 13. Don’t adjust fuel numbers just because the engine is idling too
fast. If the engine is idling too fast, adjust the airflow on the throttle plate set screw, then recheck and
adjust the RPM FUEL ranges where the engine is idling. Usually keeping RPM FUEL numbers from 500
through 1200 equal is also a good idea. This will help keep the idle from surging up and down.
If idle still seems a bit unstable, then you may need to also adjust a few MANIFOLD PRESSURE values
to improve smoothness. To do this, press the Gauge button to see gauge1 mode, note the MP reading
on the top left. Then scroll left and into the manifold pressure values, just above and below where the
engine is idling at, and make the values all equal. We have done this by default around 10” vacuum, but
some adjustment might be needed. If the MP fluctuates over more than 3 ranges, you may have to install
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