mtngun
Addicted to ArboristSite
I bumped into this issue recently when I discovered that removing my 084's spark screen boosted power considerably, even though the screen area was 2 1/2 times the area of the exhaust port.
Turns out there's a formula to calculate % open area of a screen.
My 084 screen is made of 0.018" thick wire, and there are 28 holes per inch.
Mesh spacing = 1"/28 = 0.0357"
% open area = 25 %
So ...... the screen area needs to be 4 times as big as the target area...... and the target area is generally 85% of the exhaust port area.
084 exhaust port area = 616 smm
85% port = 523 smm (and my enlarged muffler exit was about that big )
Required screen area = 4 x 523 smm = 2093 smm
The stock screen is only 1488 smm, when it needed to be 2093 smm.
At least now I know what to aim for when I'm modding a muffler.
Turns out there's a formula to calculate % open area of a screen.
My 084 screen is made of 0.018" thick wire, and there are 28 holes per inch.
Mesh spacing = 1"/28 = 0.0357"
% open area = 25 %
So ...... the screen area needs to be 4 times as big as the target area...... and the target area is generally 85% of the exhaust port area.
084 exhaust port area = 616 smm
85% port = 523 smm (and my enlarged muffler exit was about that big )
Required screen area = 4 x 523 smm = 2093 smm
The stock screen is only 1488 smm, when it needed to be 2093 smm.
At least now I know what to aim for when I'm modding a muffler.