Engine Testing - General Information Section 14 - Engine Testing - Group 14 M11 Page 14-8 Intake Manifold Boost Pressure Correction Factors Boost pressure measured in the intake manifold is directly related to the ambient temperature, the temperature rise across the air cleaner and turbocharger, and the pressure drop across the charge air cooler. Typically when the ambient temperature rises, the boost pressure measured in the intake manifold decreases. Conversely, higher boost pressure measured in the intake manifold can be ob- tained with falling ambient temperature.
Refer to the following procedure and boost pressure cor- rection factor charts to aid in the determination of engine performance output. The charts define power output by modifying boost pressure as a function of intake manifold air temperature. To use the charts, first determine which chart is appro- priate for your engine. Select the proper chart based on the local area altitude and the engine horsepower stamped on the dataplate. With the engine running at full load and full throttle at maximum horsepower RPM, the following data must be taken. Two pressure measurements are required: 1.
Measure the turbocharger compressor outlet pressure (boost) between the turbocharger and the charge air cooler using a calibrated pressure gauge. 2. Measure the intake manifold pressure at the 1/8 inch NPT tap in the intake manifold connection with the air horn using a calibrated pressure gauge. NOTE: The most accurate and reliable readings are ob- tained using the same pressure gauge to measure both the turbocharger compressor outlet pressure and the intake manifold pressure. Two temperature measurements are required: 1. Measure the turbocharger compressor inlet tempera- ture by inserting a Fluke digital thermometer, Part No. 3822666, and thermocouple wire kit, Part No.
3822988, underneath the intake air inlet elbow which is between the air cleaner and the turbocharger.