Air filter flow
Thread Starter
TECH Junkie
Joined: Mar 2002
Posts: 3,019
Likes: 0
From: memphis tn
Air filter flow Most people look for the latest offering from K&N,Green filter or who ever,but can they actually expect to meet the needs of a maximum effort NA or FI motor?An over the counter kit might optimisticly flow 600cfm vs a motor that needs 1200cfm plus.What options are available?On pure racing applications no filter is an option,but for the rest of us some type of filter is a reality.What are you guys using?
You're looking at it backwards when you look at the
manufacturers' "flow ratings". Which are so fine-print
massaged and hype-filled as to be worthless. Most of
them I've seen do not even state their pressure drop
test value.
Plain paper filters are pretty low restriction to begin with,
it would be pretty simple for you to quantify the pressure
drop with about 20' of vinyl tubing and some water. One
end of the hose below and one above the filter element,
middle in the cabin with a foot of water in the bottom of
the loop, see the max difference it pulls at WOT. Then
figure out what fraction of a percent difference it might
make, to manifold pressure and there's your peak HP
factor to gain.
You should see inches of water (I saw fractional inches
pulling across filters with a shop vac, years back). This
is a tiny fraction. 4"H2O=1kPa=1% left on the table. In
the spirit of "max effort" you might want to chase that
last percent. If it turns out to be a whole one.
manufacturers' "flow ratings". Which are so fine-print
massaged and hype-filled as to be worthless. Most of
them I've seen do not even state their pressure drop
test value.
Plain paper filters are pretty low restriction to begin with,
it would be pretty simple for you to quantify the pressure
drop with about 20' of vinyl tubing and some water. One
end of the hose below and one above the filter element,
middle in the cabin with a foot of water in the bottom of
the loop, see the max difference it pulls at WOT. Then
figure out what fraction of a percent difference it might
make, to manifold pressure and there's your peak HP
factor to gain.
You should see inches of water (I saw fractional inches
pulling across filters with a shop vac, years back). This
is a tiny fraction. 4"H2O=1kPa=1% left on the table. In
the spirit of "max effort" you might want to chase that
last percent. If it turns out to be a whole one.
A filters a filter. A filter is designed to clean air, it is not the area that you really want to try to make HP at. Sure you could make a few extra HP at the expense of getting dirtier air in your engine.
??
Originally Posted by brad8266
A filters a filter. A filter is designed to clean air, it is not the area that you really want to try to make HP at. Sure you could make a few extra HP at the expense of getting dirtier air in your engine.
Not true, if the filter is sized to handle the air required by the engine.
CI x max rpm
__________ = Filter in Sq inches required.
20839
You can use the VE of the engine to refine this value, if needed.
CFM of the engine = Ci x max rpm
__________
3456
The VE could be used here, too.
