5.4
9850068 R01 - 2020-2021 RZR PRO XP / XP 4 Service Manual
© Copyright Polaris Industries Inc.
EFI OPERATION OVERVIEW
The EFI system is designed to provide peak engine performance with optimum fuel efficiency and lowest possible
emissions. The ignition and injection functions are electronically controlled, monitored and continually corrected during
operation to maintain peak performance.
The central component of the system is the Bosch ME17 Electronic Control Unit (ECU) which manages system
operation, determining the best combination of fuel mixture and ignition timing for the current operating conditions.
An electric fuel pump is used to move fuel from the tank, through the fuel supply line, to the fuel rail. Fuel pressure
regulators located in the tank and on the end of the fuel rail, maintain system operating pressure and return excess fuel
back into the fuel tank. At the engine, fuel fed through the fuel rail supplies fuel to the injectors, which inject into the
intake ports. The ECU controls the amount of fuel by varying the length of time that the injectors are "on." This range
can vary depending on fuel requirements. The controlled injection of the fuel occurs every other crankshaft revolution,
or once for each 4-stroke cycle. When the intake valve opens, the fuel/air mixture is drawn into the combustion
chamber, ignited and burned.
The ECU controls the amount of fuel being injected and the ignition timing by monitoring the primary sensor signals for
intake air temperature, manifold absolute pressure (load), engine temperature, engine speed (RPM) and throttle
position. These primary signals are compared to the programming in the ECU computer chip, and the ECU adjusts the
fuel delivery and ignition timing based on these values.
During operation, the ECU has the ability to re-adjust temporarily; providing compensation for changes in overall
engine condition and operating environment, so it will be able to maintain the ideal air/fuel ratio. During certain
operating periods such as cold starts, warm up, acceleration, etc., a richer air / fuel ratio is automatically calculated by
the ECU.
EFI / FUEL SYSTEM
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