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Fuel Return Ratio
The FUEL RETURN vs FUEL CONSUMPTION RATIO is ABOUT 2 to 1.
That is, 2 gallons are returned for each gallon burned (3 gallons total supply flow)
NOTE: I have read where others state the ratio at about 1:1 - so caveat emptor applies!
FUEL FLOW RATIO:
A diesel engine’s TOTAL FUEL FLOW RATE is often cited as APPROXIMATELY: horsepower x 18% = gph
thus a 30-hp diesel would have a theoretical total flow rate of 5.4 gph. (30 x 0.18 = 5.4)
Diesel engines consume about 1 gallon per hour for every 18 hp used. You can estimate the number of gallons consumed per hour by multiplying horsepower used by 0.055.
thus a 30-hp diesel would have a conservative theoretical consumption rate of 1.65 gph (30 - 18 or 30 x 0.055 = 1.65)
NOTE: This is an obvious approximation, as diesel''s have widely varying operating curves.
The Return rate would be Total Flow less Consumption = Return
thus (from above)
5.4 Flow - 1.65 Consumption = 3.27 gph Return
3.27 return divided by 1.65 consumption = 1.98:1 Return / Flow Ratio
hence the Rule of Thumb:
Return is Twice Consumption (henceTotal Flow is 3 Times Consumption)
5.4 Flow divided by 1.65 Consumption = 3.27:1 Flow/Consumption Ratio