Understanding: FRC Fuel Limit and Boost Pressure on Caterpillar Engines
FRC - Fuel Ratio Control
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| Figure 1.1 - Boost Pressure (3512C Engine) |
FRC Fuel Limit
The flash file inside the Engine ECM sets certain limits on the amount of fuel that can be injected. The FRC Fuel Limit is a limit that is based on the Boost Pressure. The Boost Pressure is calculated as the difference in pressure between Atmospheric Pressure and Turbocharger Outlet Pressure (refer to Figure 1.1 above).
#Abnormal reading for Boost Pressure while Ignition switch ON and Engine Idle/700 RPM (8-9 Psi).
→FRC Fuel Limit - 164.4
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| Figure 1.2 - Boost Pressure (8 psi) |
→Replace the Turbocharger Outlet Pressure Sensor (with CAT P/N 194-6724). Normal reading for Boost Pressure on Engine Idle/700 RPM (0 psi).
→FRC Fuel Limit - 117.8
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| Figure 1.3 - Boost Pressure (0 psi) |
The FRC Fuel Limit is used to control the air/fuel ratio for control of emissions. When the Engine ECM senses a higher Boost Pressure, the Engine ECM increases the FRC Fuel Limit.
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| Figure 1.4 - FRC Fuel Limit (171.1) |
A higher Boost Pressure indicates that there is more air in the Cylinder. When the Engine ECM increases the FRC Fuel Limit, the Engine ECM allows more fuel into the Cylinder.
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