5.2 Basic engine constants 5 SETTING UP A BASIC CONFIGURATION
fuel used, such as 14.7 for gasoline or 9.85 for E85 ethanol blends. Note that you will want to run this after
entering the injector size and displacement numbers, below.
• Control Algorithm - This setting controls the method with which engine load is calculated. Engine load
represents how hard the engine has to work and can be based on many factors such as manifold pressure,
throttle position, air mass, or combinations of these. Note that this setting only sets the control algorithm for
fuel injection and related settings; it does not set the control algorithm for ignition and related settings. You
may use different algorithms for different tables. The following settings may be selected.
– Speed Density - Use the MAP (Manifold Absolute Pressure) sensor to determine load. In this case, the
vertical axis of any fuel table lookup is in kilopascals (kPa). The maximum value reported by the MAP
sensor (in non-turbo applications) will be the same as the barometric pressure.
– Percent Baro - This setting is similar to the Speed Density setting in that the MAP sensor is used to
determine load. However, instead of directly using the manifold pressure, the manifold pressure is
divided by barometric pressure to give a percentage of barometric pressure. This setting can be useful
for those who regularly drive at high altitudes. It ensures that regardless of barometric pressure, all
table lookups operate over 0-100%. For example, if barometric pressure is 80 kPa, and the engine is
operating at 50 kPa, the actual value used for table lookups is 50kPa/80kPa or 62.5%.
– Alpha-N - Use the throttle position to determine load on the engine. Be sure to calibrate the throttle
range using Tools -> Calibrate TPS before using this setting.
– MAF - Use the MAF sensor and related calculations to directly determine the amount of fuel to inject. In
this mode, the VE table is not used to determine the amount of fuel to inject.
– ITB - This mode was created specifically for naturally aspirated engines running with independent throt-
tle bodies. It combines alpha-n (at high engine loads) with speed density (at low engine loads), using
the load calculation that makes the most sense at each RPM. For example, most ITB setups do not
have good vacuum at idle or low RPM, and slightly touching the throttle makes them lose all vacuum,
but at higher RPM start to respond more like a traditional single throttle body engine. This mode allows
the use of speed density at low engine loads and switches to alpha-n at high loads, with an adjustable
switchpoint curve over RPM.
• Squirts Per Engine Cycle - Only used when running batch fired injection. Determines the number of times
per engine cycle (two revolutions on a four-stroke engine) injectors are squirted when in a batch injection
mode. This setting has no effect when injecting sequentially.
• Injector Staging - This setting is used only in batch injection modes. It determines whether the two injection
channels are squirted at the same time, or in an alternating fashion.
• Engine Stroke / Rotary - Specify whether the engine is a four or two stroke piston engine, or a Wankel rotary
engine. The rotary mode allows for trailing spark outputs on Mazda and other dual plug rotary designs.
• Number of Cylinders / Rotors - Sets the number of cylinders for the engine. The MS3Pro can run sequential
injection on up to 12 cylinders.
• Engine Type - Determines whether the engine is an even-fire engine or odd-fire engine. An even fire engine
is an engine where the crankshaft moves an equal number of degrees between each cylinder’s top dead
center (TDC). An odd fire engine may have a different number of degrees between TDC on some cylinders
when compared with others. You are only likely to see odd fire settings on certain V6 models, “crossplane”
inline fours and split crank parallel twins (found on some motorcycle engines), and V type engines having
less than 6 cylinders. Normal V8, inline four, and inline six engines are all even fire.
• Engine Size and Injector Size are used for MAF fueling and the Required Fuel calculator.
• Main fuel outputs - This should be set to “Injector A, B...” Fuel for all normal MS3Pro installs. This is
included to allow you to check tune files imported from standard MS3s. It can be set to use only injector I
and J, but this is mostly to maintain compatibility with MS3 V3.0 / V3.57 tune files.
• Sequential On - The injector sequencing may be set to three different modes.
AMP EFI MS3Pro manual version 1.202, firmware 1.5.0, 4/21/2017 Page 53
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