Filter Minders for Dummies

[davidbrady]

Since I don't know what the restriction of the air filter is I'm going to replace it with a 7" 90 deg elbow and I'm going to calculate the pressure drop, in inches of H20, for my LXi intake ductwork (all the intake pipe-work, from atmosphere at the inlet bell to the turbo, minus the air cleaner):

I have two 90 deg long radius, 6" diameter elbows:
Equivalent Straight: L = 20(6)/12 = 10 ft,

I have one 90 deg long radius, 7" diameter elbow:
Equivalent Straight: L = 20(7)/12 = 11.67 ft

I have 3 feet of straight 6" pipe joining the turbo to the air filter.

I have 2' of straight 7" pipe joining the inlet bell to the top of the air filter.

A 500 HP Detroit Diesel Series-60, at full tilt, moves Q = 1170 cfm of air at standard conditions.

The density of air at 65 deg F is: S = 39.6/(65+460) = .0754 lb/cu ft

The pressure drop of an equivalent length section is: L*S*Q**2/(187*D**5) in of H2O

Pressure drop of 6" pipe (two elbows plus straight): (10+10+3)*.0754*1170**2/(187*6**5) = 1.63 in H2O

Pressure drop of 7" pipe (one elbow plus straight): (11.67+2)*.0754*1170**2/(187*7**5) = 0.449 in H2O

Total pressure drop of the intake duct = 1.63 + 0.449 = 2.08 in of H2O