Filter Minders for Dummies

[davidbrady]

Pressure differences between the throat of the intake opening and the intake tube within 5" of the turbo is what we want to measure. The FM can't do this - another reason not to base design decisions on it.

The FM is a tire pressure gauge. It measures vacuum relative to its ambient pressure which is the pressure of the engine compartment. How much positive pressure do you think the fan at full tilt creates. As ambient pressure increases so does the FM's perceived intake tube pressure drop.

Folks, DD specs a clean air filter system at 12" of H2O and a dirty one at 20. That 8" difference is 0.30 psi or about the pressure developed when you blow out your birthday candles. Another perspective: take an LXi with slide open, now close the slide, the room pressure increased by one psi.

Don't rely on the filter minder to guide you in cutting metal. More precise investigation is needed.