Installing an After-Turbo Pyrometer in the M35A2.

The purpose of this work is to measure the turbocharger exhaust temperature, as a guide to driving the truck and to determine if it is safe to increase the fuel delivery rate slightly. On hard driving, the truck laden to a GVW of 20000 LBS at 55MPH charging up a hill and being drastically slowed by this act, was barely able to push the pyro to 900 degrees. The pyro guage rests at 50 degrees even with nothing connected. Adjustment required, or normal? Hmm. The thermocouple is mounted 2" downstream of the exhaust turbine outlet. It should be safe to go to 1000 degrees. The goal is to get enough power to avoid slowing down to 35MPH when climbing those steep hills. The lamp in the guage is a 12V lamp. It operates from an auxiliary 12V power source in the truck. To prolong lamp life the voltage to the lamp was reduced by about 10% by the use of a 3.9 ohm 2 watt series resistor. The welding of the pyrometer mount to the pipe was done with a TIG welder. Use caution removing and installing the pipe. Right behind it, next to the engine, is the starter solenoid with exoposed 24VDC. The sparks will fly. The thermocouple leads polarity is such that yellow is positive, and red is negative. Go figure.

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