Here is some flowbench work done by a member over on AS.
Some interesting results...
Open Plate Configuration CFM @ 28"H2O CFM @ 25"H2O CFM @ 10"H2O see Pic: 2 1/2" ID orifice plate, flowed at 28"H2O
Stock HD Filter Notes:
filter only 227.2 214.7 135.9 2 Prewrap caused 60% drop in flow
filter & prewrap 135.5 128.0 81.0 3
Max-Flow Filter
dry 60-pore filter only 186.1 175.9 111.3 4 Notes:
dry 60-pore filter & nylon 152.5 144.1 91.2 5 Nylon caused 20% drop in flow to both foam elements
oiled 80-pore filter only 144.2 136.3 86.2 6 Outers caused 7% drop in flow
oiled 80-pore filter & Outers 134.0 126.6 80.1 7
oiled 80-pore filter & nylon 114.2 107.9 68.3 NA
Intake System Configuration CFM @ 28"H2O CFM @ 25"H2O CFM @ 10"H2O see Pic: Stock carb - WOT - 0.8125" orifice plate, flowed at 28"H2O
Stock HD Filter Notes:
no filter; open backplate/radius inlet 41.8 39.5 25.0 NA Prewrap accounts for <4% drop
filter only 40.2 38.0 24.0 8 Cover accounts for 0.4CFM drop on average
filter & prewrap 38.8 36.7 23.2 9 Deflector accounts for 1.0CFM drop
filter, prewrap, & cover 38.2 36.1 22.8 10
filter, prewrap, & deflector 37.2 35.2 22.2 9 also
filter, prewrap, deflector, & cover (stock Stihl) 37.0 35.0 22.1 10 also
Max-Flow Filter Notes:
dry 60-pore filter only 41.1 38.8 24.6 11 w/Dry 60-pore filter, virtually no loss if run w/nylon or Outers
dry 60-pore filter & nylon 41.0 38.7 24.5 12 Again, deflector accounts for 1.0CFM drop
dry 60-pore filter & cover 41.0 38.7 24.5 13 MF rain cover causes virtually no drop in flow
dry 60-pore filter & deflector 40.1 37.9 24.0 11 also
dry 60-pore filter, deflector & nylon 40.0 37.8 23.9 12 also
dry 60-pore filter, deflector & cover 39.9 37.7 23.9 13 also
oiled 80-pore filter only 41.0 38.7 24.5 14 w/Oiled 80-pore filter, virtually no loss if run w/nylon or Outers
oiled 80-pore filter & nylon 40.9 38.7 24.5 15 Again, deflector accounts for 1.0CFM drop
oiled 80-pore filter & Outers 40.9 38.7 24.5 16 MF rain cover causes virtually no drop in flow
oiled 80-pore filter, Outers & cover 40.9 38.7 24.5 17
oiled 80-pore filter, Outers & deflector 39.9 37.7 23.9 16 also
oiled 80-pore filter, Outers, deflector, & cover 39.8 37.6 23.8 17 also
I don't know if it is ok to post a link to the thread.
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