Ever wonder about the accuracy of your Filter Minder attached to your air cleaner and what the various markings on it translate to in common pressure values?

Related to that, are the references to "PSI", "inches of vacuum", "inches HG" and similar units commonly used in various atmospheric measurements - some of us get careless (including me!) in making pressure references, when actually there are vast differences in units between PSI and inches of vacuum, etc.

Here's a handy conversion table, displaying the relationship between 1 PSI and various other common units of measure:



As can be seen, there's a substantial difference between them!

I wanted to point that out before starting with the following demo of readings taken on my own '02 truck's Filter Minder, so a proper perspective could be arrived at.

Below is the zero reading as displayed on my own vacuum pump designed to bleed brakes and test emissions devices, it reads in "inches HG", and as can be seen, the Filter Minder is not yet deflected



And here is a shot with the Filter Minder at full deflection - and the vacuum gauge indicating about 2 inches HG:



From this, a reasonable estimate can be made as to the readings on the Filter Minder between zero and 100% - and as can also be seen, at least for my specific Filter Minder, 100% occurs at about 1 PSI flow across the filter element itself - or about 27 column inches of water. This is the point DC recommends that the filter element be changed.

There are a number of related points of interest as far as atmospheric pressure seen at the intake of our engines is concerned - such as the actual measured efficiency of various aftermarket air ducting and filtering devices as compared to the stock setup - what do they actually provide in improved performance and efficiency - and are actual figures/comparisons even provided?

In my own case, the stock OEM filter on my truck when it was new seemed to perform properly while the truck was stock - but as soon as I installed the Edge Comp and headed up a grade towing our 5th wheel RV, the filter minder immediately pulled down 2/3 of the way!

It was obvious that the added power and turbo boost provided by the Comp demanded better airflow!

I subsequently drilled the air filter box for increased air flow, and installed a K&N filter - and had no further issues. Later, I switched to the even better BHAF filter.

SO, it might be a good idea to get our airflow terminology straight, take a few measurements - and ASK a few questions when casual claims are made as to "better air flow" and "increased power" - talk is cheap, seat-of-pants reports aren't worth the rivets in your Levis - and actual figures are worth GOLD!