Polaris Virage TX 2000 Service Manual page 279

FFI™ FUEL INJECTION
Theory
FFI ™ Combustion Process
The FFI ™ combustion process functions in two modes: stratified and homogeneous. The engine is started in
homogeneous, idles in stratified, then smoothly transitions again to homogeneous as the engine moves to higher
RPM. For more detail on FFI™ combustion, see Introduction to FFI® Fuel Injection video, PN 9915680.
During startup, fuel is injected with the piston low in the cylinder. Air/fuel is mixed by turbulence, and multiple
plug firings occur to ensure quick starting and complete combustion.
During idle, multiple plug firings continue for each cylinder combustion event. Spark is timed to occur as fuel
reaches the spark plug tip, then is programmed to continue in a multi-strike mode. Due to fuel/air density at low
RPM, and fuel actually spraying on the plug tip, repeated plug firing ensures complete combustion.
At higher RPM, the fuel injectors supply fuel earlier in the firing sequence. Pistons are farther down the cylinder,
and air/fuel is mixed by turbulence. In this mode the mixture is more combustible, so fewer firings per combustion
event will occur. Very low amperage is required to sustain either stratified or homogeneous operation.
• Stratified: Air/Fuel mixture is layered with different ratios within the combustion
chamber.
• Homogeneous: Air/Fuel mixture is uniform throughout the combustion chamber.
Flywheel
The FFI ™ flywheel has four important functions:
• Provides a ring gear for starter motor engagement.
• Has cast-in timing encoder ribs on the outer diameter that work in conjunction with the
magnetic crankshaft position sensor to control ignition timing and fuel injector operation.
• Houses magnets that work in conjunction with the stator to provide power to operate the
ignition, injectors, EMM, MFI(multi-function instrumentation gauge), and accessories.
It contains magnets that work in conjunction with a stator to provide battery charging (12 volts) and injector opera
tion (45 volts). Within approximately one crankshaft revolution, the EMM will learn crankshaft positioning to en
able it to fire the cylinders and control spark advance.
Stator
The stator provides AC voltage to the regulator/rectifier side of the EMM where it is converted to DC voltage.
The DC power is used to charge the battery, power the EMM and run the ignition and injectors. The injectors
and and ignition are 100% driven by the stator voltage.
Capacitor
The capacitor is a voltage limiter. It prevent fluctuations in voltage that would cause erratic injector operation,
and resultant unwanted changes in fuel mixture and combustion.
ENGINE MANAGEMENT MODULE (EMM)
The Engine Management Module (EMM) has two engine harness connectors. It is a water cooled microprocessor
that receives inputs from several switches and sensors. This information is used by the EMM to control engine
operating parameters such as ignition,and fuel injection.
EMM inputs include:
• Throttle Position
• Air Temperature
• Crankshaft Position
• Water Temperature
• EMM Temperature (Internal)
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