calculating exhaust volume

[kb4bme]

Lee,

I've found a formula for calculating air volume into an engine at a given rpm, but not one for figuring exhaust volume; You got one?

<If such a critter is on the website, please direct me and forgive my year or so of absence>

[EWC]

Found these in a 96 Donaldson Exhaust catalog

Rules of Thumb

Engine Exhaust Flow Rate Calculation

[(Exhaust Temp (F) + 460)/540] x Intake Airflow (CFM) = Exhaust Flow
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Engine Type--Engine Temp--Max Backpressure

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Diesel 2-cycle N/A 900 F 4" Hg
Diesel 2-cycle Turbo 750 F 3" Hg
Diesel 4-cycle N/A 1000 F 3" Hg
diesel 4-cycle Turbo 900 F 3" Hg

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Gasoline - All Types 1200 F 4" Hg

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Efficiency calculations when manufacturer specs are not available

4 Cycle Engine Airflow Calculation

[( Engine Size (CID) x RPM ) / 3456 ] x VE* = Intake Airflow (CFM)

2 Cycle Engine Airflow Calculation

[( Engine Size (CID) x RPM ) / 1728 ] x VE* = Intake Airflow (CFM)

* Volumetric Efficiency (VE)

4-Cycle "L" Head N/A Gas Eng = .70
4-Cycle Valve In Head N/A Gas Eng = .75
4-Cycle Valve In Head N/A Diesel Eng = .90
4-Cycle Valve In Head Turbo Diesel Eng = 1.35

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As an example of all the number crunching , they provide some charts of a lot of engines and their specs i.e.

Navistar 6.9L - 3000 RPM , 170 HP , 330 Intake CFM and Exhaust Temp and Flow of 1000 F and 892 CFM

Cummins 6BT - 2300 RPM , 230 HP , 520 Intake CFM and Exhaust Temp and Flow of 910 F and 1380 CFM