Ambient Air Density Derate
Due to the air handling limitations and stringent emissions regulations, engine torque output will be limited at high altitude operating conditions. This aggressive protection, seen as a fueling derate, is necessary to protect the turbocharger from excessive temperatures and turbocharger speed. Not only is this derate altitude related, it is also ambient air temperature related. The combination of ambient air temperature and barometric pressure is used to calculate the ambient air density. As the air density decreases (ambient air temperature increases or altitude increases), the turbocharger speed increases and a derate is necessary to control the turbocharger speed to under set limits. In INSITE™ electronic service tool, the user fueling state will display air density limit state.
Fault Code 1943 will be logged indicating that the engine torque was reduced because of high altitude operation.
Altitude Derate Based on Turbocharger Speed
Due to turbocharger mechanical limitations, the ISX and ISM engines will encounter a severe fueling derate if a calibrated turbocharger speed is achieved. This calibrated threshold is set much higher than the turbocharger speed derate threshold described later. This derate is time based and is severe at first. The derate progressively decreases as time elapses. In INSITE™ electronic service tool, the user fueling state will display altitude derate.
Turbocharger Compressor Outlet Air Temperature Derate
Due to turbocharger temperature limitations, ISX and ISM engines will encounter a charge derate if a calibrated turbocharger compressor outlet air temperature is achieved. This derate is temperature based and will increase in severity as the turbocharger compressor outlet air temperature continues to increase. In INSITE™ electronic service tool, the turbocharger compressor outlet air temperature derate will display Active if this derate is active. No loss in power will be felt during this derate, assuming the user fueling state in INSITE electronic service tool does not display any type of derate. If the turbocharger compressor outlet air temperature continues to rise and the charge derate becomes severe enough, the exhaust gas temperature could reach a calibrated threshold and a turbocharger fuel control derate could be incurred. Fault Code 2347 will be logged when the engine is derated for high compressor outlet temperature conditions.
Turbocharger Speed Derate
Due to turbocharger mechanical limitations, ISX and ISM engines will encounter a charge derate if a calibrated turbocharger speed is achieved. This calibrated threshold is set much lower than the altitude derate threshold described previously. This derate is speed based and will increase in severity as the turbocharger speed continues to increase. In INSITE™ electronic service tool, the turbocharger speed derate will display Active if this derate is active. No loss in power will be felt during this derate, assuming the user fueling state in INSITE™ electronic service tool does not display any type of derate. If the turbocharger speed continues to rise and the charge derate becomes severe enough, the exhaust gas temperature can reach a calibrated threshold and a turbocharger fuel control derate could be incurred.
Turbocharger Fuel Control Derate
Due to turbocharger temperature limitations, ISX and ISM engines will encounter a fueling derate if a calibrated exhaust gas temperature is achieved. There is no physical sensor in the engine for this temperature. This temperature is calculated by the electronic control module (ECM) and can be monitored in INSITE™ electronic service tool. The parameter name is exhaust gas temperature (calculated). In INSITE™ electronic service tool, the user fueling state will display turbocharger fuel control state. Fault Codes 2451 or 2346 will log if the engine is derated due to high turbine inlet temperature conditions.
Engine Protection Derate – Fueling Derate
Several temperatures and pressures in the ISX and ISM engines have engine protection associated with them. The first phase of engine protection is a fueling derate. This derate is severity based and as the temperature increases, the severity of the fueling derate also increases. Likewise for pressure, as the pressure decreases, the severity of the fueling derate increases. Temperatures that utilize a fueling derate are engine coolant temperature, intake manifold air temperature, EGR temperature, and turbocharger compressor outlet air temperature. The oil pressure is the only pressure that utilizes a fueling derate. In INSITE™ electronic service tool, the user fueling state will display engine protection derate.
Engine Protection Derate – Speed Derate
Several temperatures and pressures in the ISX and ISM engines have engine protection associated with them. The second phase of engine protection is a speed derate. This derate is time based. After a set period of time spent above a calibrated temperature or below a calibrated pressure, the speed derate will ramp into effect. The speed derate will lower the maximum allowed engine speed to a calibrated speed. Temperatures that utilize a speed derate are engine coolant temperature, intake manifold air temperature, engine oil temperature, and exhaust gas recirculation (EGR) temperature. The oil pressure is the only pressure that utilizes a speed derate. In INSITE™ electronic service tool, the user fueling state will display engine protection derate. If the Engine Protection Shutdown feature is enabled, the engine will be shut down after a set period of time in speed derate.
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