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Exhaust Pipe Sizing & Backpressure

Exhaust flow, gas velocity, and estimated backpressure for a run with bends, against the engine's allowable limit.

Inputs

Inputs and assumptions

Diesel sets move roughly 2.5 to 4 cubic feet per minute per kW. Use the data sheet where available.

Never use a pipe smaller than the engine outlet.

Each 90 degree bend adds the equivalent of about 8 feet of straight pipe.

Many diesel packages allow 20 to 30 inches of water; check the data sheet.

Result

Estimated backpressure
—
Equivalent straight length
—
Exhaust flow
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Margin under the limit
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Exhaust velocity
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What to check

  • Engine manufacturer allowable backpressure in inches of water
  • Exhaust gas temperature and actual run geometry

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