3512B Petroleum Engines Caterpillar

The ECM automatically compensates for engine operation at higher elevations. The ECM derates the fuel delivery according to the barometric pressure. The barometric pressure is sensed by the atmospheric pressure sensor. The atmospheric pressure has an effect on the performance of the engine. Derating the fuel delivery maintains the temperatures of the exhaust gas within acceptable limits.

The derating of the engine starts at a specific barometric pressure. The barometric pressure is equal to the atmospheric pressure of an elevation. The atmospheric pressure is specific for the engine and for the engine rating. The default settings that are programmed at the factory are listed in Table 1.

Table 1

Altitude
Parameter	Default Setting
Derate setpoint	2T specification
Security level	Required password
Derating per 305 m (1000 ft)	3%
Maximum derating	35% of the rated power

If the barometric pressure is below the setpoint, a warning and a derating will occur. The continuous schedule of the derating is three percent per 1 kPa (.15 psi) of pressure below the setpoint. The maximum derating is 35 percent.