The Filter Minder® air filter service indicator
measures vacuum in the air induction system in 'inches of
water vacuum.'
The Filter Minder® is calibrated per
engine or vehicle manufacturer's recommendations.
Most diesel engines operate at a maximum 20 to 25 inches
water vacuum under full load.
Gasoline
engine calibrations can vary depending on the engine size
and air cleaner design. Small gas engines (2-5 HP) should
usually limit restriction to 3 inches maximum, 6-25 HP should
limit filter restriction to 8" maximum, and most gasoline
engine powered automobiles 20 inches maximum.
Some
vehicles with the Filter Minder® as
standard equipment may use a higher calibration than the
above guidelines. If in doubt, contact Engineered Products
Co. for recommendations.
Diesel
suction fuel filters are usually monitored in inches of
mercury. The maximum restriction is typically 10-12 inches
of mercury.