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You should aim for a 0 value when the engine is at normal operating temperature. Most engines will
not require extra fuel after 100-140 degrees F. The values should decrease in a fairly linear fashion
from cold to operating temperature then have 0's entered above this threshold. Temperatures can be
displayed in F or C.
As a reference, a value of 127 would add 50% to the pulse width and a 255 entered will double the
pulse width.
By flicking back between Gauge 1 mode and ENGINE TEMPERATURE you can make adjustments
while the engine is warming up. Each time the EM-5 updates to a new ET in gauge mode, you can go
to that ENGINE TEMPERATURE range in the programmer. Now turn the knob richer and leaner and
note where the engine starts to run rough on each side of 12 o’clock. If it runs rough say at 10 and 2
o’clock, you probably have the engine temp values about right. If not, adjust the ENGINE TEMP value
at the engine temp displayed currently in Gauge1 mode.
Start (START)
Start enrichment is provided for under the START and START CYCLES parameters. The EM-5 reads
the signal from the engine temperature sensor, looks up the START value at that temperature range,
and injects extra fuel for a certain number of engine cycles after the EM-5 detects crank rotation. This
function is activated every time that the engine is started, no matter what the engine temperature is.
However, if there is a zero at the current temperature range, no extra fuel will be added. START
values are critical for proper starting, especially in cold climates.
At colder temperatures, the values are high, tapering off as the engine warms up. At temperatures
over 100 to 140°F, most engines do not require much extra fuel so the values should be low or 0 here.
Experimentation is required for a satisfactory setup here.
It is best to not open the throttle during cranking, especially in cold temperatures. Opening the
throttle will cause a leaner mixture during cranking. The engine needs a rich mixture to start.
Tuning all the START values will take many days in very cold climates. You can usually only tune one
value per day, and you will have to wait for colder weather to adjust the colder ranges.
Systems will do 1 injection of fuel at key-on, when the Start value is greater than 0 at any
temperature. This will improve cold starting.
Aviation systems have special software to allow manual priming without the engine turning over. You
may stroke the throttle a few times in cold conditions to open the injectors momentarily. This acts just
like a primer and may aid starting in very cold climates. Close the throttle when cranking, even if
you prime.
Start Cycles
The value entered under START CYCLES determines how many engine cycles START enrichment
lasts for. This is the number of crank revolutions times 2 on a 4 stroke engine. Some engines require
start enrichment lasting a long time, others only require a short start enrichment period. The larger the
value under START CYCLES, the longer the enrichment period. This is adjustable between 0 and
255, but a value of 40 is probably as high as you would ever need, and do not set this below 10
because too low a value will make the START function expire too quickly.
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