7.1 Basic / Load Sections 7 ADDITIONAL ITEMS: BEYOND BASIC FUEL AND IGNITION CONTROL
Observe the large variation in MAP signal during the 720 degree cycle. It can be seen that one MAP window
falls on the intake stroke (where the MAP reaches a minimum) and the next MAP window is on the power stroke
(MAP is near atmospheric.) On this engine it was important to set the appropriate MAP sample angle and window
width to capture the dip in MAP, and set the number of events to 2, since the intake happens every two revolutions.
The ideal MAP sample angle may either be determined by:
• using the MAP logger (registered TunerStudio only) and opening the datalogs created in MegaLogViewer to
ensure the MAP window aligns with the dip in MAP
• by watching the MAP gauge on the TunerStudio dash and adjusting the MAP sample angle in (say) 10 degree
steps until the minimum is found.
Note that on most engines the best sample angle will vary with RPM. The Window Width should be set so that it
covers the dip repeatably.
The sample data below shows a practical example from the above test engine with a short sample of the data.
First - with No. Events set to 1.
Event no. Min MAP in window MAP used for fueling
1 70 70
1 98 98
1 70.5 70.5
1 98 98
The MS3Pro is sampling the MAP reading on both the intake stroke and the power stroke; the intake strokes
have a low MAP reading, but the pressure on the power stroke is nearly atmospheric. This results in the MAP
bouncing around between 70 and 98 resulting in unpredictable tuning. Using Event Average would be equally
poor.
Now - with No. Events set to 2.
Event no. Min MAP in window MAP used for fueling
1 70 70
2 98 70
1 70.5 70.5
2 98 70.5
This gives a more realistic and more repeatable MAP signal and is a good start for tuning - the atmospheric
readings of 98kPa on the "dead" windows are ignored.
The Phase detect threshold is in use on this particular engine. It allows 1cyl and certain 2cyl engines to run
sequential fuel and spark without a cam sensor. The MS3Pro "looks" at the MAP signal during the reading and
compares it to the threshold to determine whether this is an intake stroke.
AMP EFI MS3Pro manual version 1.202, firmware 1.5.0, 4/21/2017 Page 141
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