A direct acting, pneumatically controlled governor for a diesel engine operates in a range of 10 to 50 psi. The fuel rack position is at 20 millimeters when the governor air pressure is 30 psi. If the governor air pressure changes to 20 psi, the fuel rack setting will change to __________.
• Proportional relationship between governor air pressure and fuel rack position • How to use linear interpolation or a straight-line relationship between two variables • Setting up a simple formula of direct variation (y = mx + b) using known values
• If fuel rack position changes in direct proportion to air pressure, what happens to rack position when pressure decreases? • Can you treat the pressure–rack movement relationship as a straight line and find the slope using the known point and range? • Once you find how many millimeters of rack movement correspond to 1 psi change, how far will the rack move when pressure drops from 30 psi to 20 psi?
• Confirm that the problem implies a linear (straight-line) relationship over the 10–50 psi range • Carefully calculate the change per psi based on the full governor range and corresponding rack movement range (you may need to deduce this) • Check that your final rack setting is between reasonable limits for the given range (it should not be outside the likely minimum or maximum rack positions)
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