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Magnet Seen/Not Seen window
This window is used to check hall sensor alignment with magnets. To check alignment you must rotate
the crankshaft very slowly by hand. Some SDS Hall sensors are adjustable, so sensor alignment with
magnets is very critical to system operation.
The LCD window will change to SEEN when a magnet is over the sensor. Check all magnets for being
SEEN if troubleshooting a no start condition or misfire at higher RPM’s. Each magnet should be SEEN
for at least 2 to 3 degrees of crank rotation. This window is not valid if the engine is running.
Basic SDS Fuel Tuning
Important programming and tuning tips:
CLOSED LOOP MUST be turned OFF when programming fuel values, and it is normally off when
shipped from the factory. We highly recommend using a wideband mixture meter O2 sensor to aid in
tuning.
Let the engine reach full operating temperature before fine tuning any MAP or RPM values. If you try
reprogramming while the ECU is still adding extra fuel for warmup, you are wasting your time and getting
off track.
You must vary only one parameter at a time and observe the AFR meter. If you change both rpm and
MAP, you don't know which parameter is affecting the air/fuel ratio. Hold MAP constant and vary rpm or
vice versa, never both.
It’s vitally important that you understand- injector open time (the amount of fuel injected) is a
result of the RPM FUEL value TIMES the MAP FUEL value. RPM values address fueling changes
related to volumetric efficiency (engine breathing). MAP values address load. These are two
separate parameters which come together in the ECU to determine how much fuel is injected.
Make absolutely sure that fuel pressure is staying where it should, that all injectors flow the same
volume, have good patterns and that injectors, filters and pumps have sufficient flow rates to feed your
engine at full power. No amount of programming will fix inadequate fuel flow caused by a
mechanical fuel system problem.
You should first become familiar with all the different programmable parameters by reading the main
SDS manual.
Improper programming of fuel and ignition parameters can cause engine damage and a complete power
loss in extreme cases.
Background Technical Information
Air/ fuel Ratio
In most spark ignition, internal combustion engines, the mixture is combustible within an AFR (air/fuel
ratio) range of roughly 9 to 1 to about 18 to 1. 9 being very rich, 18 being very lean. 14.7-15.2 is the
stoichiometric ratio (chemically correct) for lowest emissions. Best power is obtained at around 12.5 for
most naturally aspirated engines.
SDS Fuel Tuning
The fuel tuning has been written in the sequence that we recommend tuning the system. RPM FUEL
first, followed by Manifold Pressure, Acc pump, Engine Temp, Start, closed loop and fuel cutoffs/limits.
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