Western Filter Co.

Calculated Exhaust Flow Rate

Calculated Exhaust Flow Rate for a Silencer With Pressure Drop of 1.0" Hg or Less

If pressure drop requirement is 1" of Hg or less and exhaust flow rate (CFM) is known, the following chart can be used to determine silencer size without calculations. Find the lowest flow rate on the chart that is equal to or greater than the flow rate of your engine under the appropriate silencing level.

Inlet Pipe Dimension 100 200 300 400
.0031 .75 41 35 29 -
.0055 1 73 63 52 -
.0085 1.25 113 98 80 -
.0123 1.5 163 142 117 -
.0218 2 288 250 206 -
.0341 2.5 450 380 325 -
.0491 3 650 565 470 -
.0668 3.5 880 770 640 -
.0873 4 1160 1000 830 790
.1363 5 1810 1580 1290 1240
.1963 6 2600 2250 1870 1770
.3491 8 4600 3900 3340 3150
.5454 10 7200 6200 5200 4950
.7854 12 10200 8800 7500 7100
1.069 14 14000 12000 10200 9700
1.438 16 18000 15500 13700 13000
1.760 18 23000 19800 16800 16000
2.180 20 28400 24300 20900 19700
2.640 22 34400 29500 25300 24000

Inlet Pipe = Inlet Pipe Area (Ft 2), Dimension = Pipe Dimension, 100 = 100 Level Silencer, 200 = 200 Level Silencer, 300 = 300 Level Silencer, 400 = 400 Level Silencer

Note: These precalculated exhaust flow rates are based on an end in end out silencer. Please refer to specific specification sheet when determining back pressure for a side inlet or middle side inlet silencer.*