From: schludermann@sscvx1.ssc.gov
Newsgroups: rec.autos,rec.autos.tech,rec.autos.vw
Subject: Re: FRAM filters, what do the numbers mean?
Date: 10 Nov 92 01:02:22 GMT
Organization: Superconducting Super Collider Laboratory

In article <BxGwux.GC1@Interlan.com>, powell@interlan.interlan.com (Glen D. Powell) writes:
> 
> 
> Reprinted from the November '92 issue of _european car_ magazine
> and is a "side bar" to  "Project 924", a well worn 924 that they
> are rebuilding.
> 
> page 53
> 
> Fram oil filters
> ----------------
> 
>    For the last several years, we have recommended Fram Wear Guard oil
> filters because of the protection they afford automobile engines. Now,
> Fram has come out with an improved oil filter, which goes by the name
> Extra Guard.
> 
>    Fram filters have always had good single-pass efficiency ratings.
> The higher the single-pass efficiency, the more particle will be removed
> from the oil each time the oil passes through the filter. Screen type
> surface filters have poor single-pass efficiency, while depth filters
> (such as "toilet ((no, not toyota, ed.)) paper" filters) generally have
> high singel-pass efficiency. During Fram's on-going testing program, they
> determined that single-pass efficiency is one of the best ways of
> determining filter effectivness. Thus, the goal was to better their already
> good single-pass efficiency.
> 
>    The trade-off is that as single-pass efficiency rises, restriction often
> rises, too. Thus, a screen-type filter (when clean) offers little restriction,
> while a "toilet paper" filter is very restrictive.
> 
>    To increase single-pass efficiency while controlling restrictiveness,
> Fram switched from their highly evolved resin-coated cellulose fiber
> element to a hybrid element made of glass fibers and resin-coated
> cellulose fibers. The coated cellulose fibers give the element the strength
> it needs (very omportant in Volkswagen applications, as we have learned),
> while the glass fibers act as barbs to catch particles. New construction
> techniques give the Fram Extra Guard filter the characteristics of both a
> surface filter and a depth filter.
> 
>    The result is an increase in single-pass efficiency from 92.4% in the
> Wear Guard series to 96.3% in the Extra Guard Series, with no increase in
> restrictiveness (both filters are rated only 3 psi pressure drop).
> 
>    Project 924 may have been abused in the past, but from now on it gest
> nothing but the best.
> 
> -glen
> 



  A few points missing here. The efficency rating given here is at what
particle size?  The good pleated surface filters give out at 10-15 microns.
Dirt particles this size are within the wear zone for engines. Depth type
filters usually go down to 4 microns. In addition to being able to capture
and retain combustion moisture, which will react with the oxygen, petroleum
free radicals, combustion byproducts and heat to form acids, sludge & varnish.
True the pressure drop across the filter is greater for depth filters, that
in it's self is no indication of loss of lubrication. In my experience the
depth filters never lost more than 15 psi at 5000-7000+rpm (in a datsun). An
abrupt change in direction did more to affect the oil pressure. IMHO I'd
rather experience a brief period of by-passing cleaner oil than a grittier
slurry. The thing to do is install one of those high efficency submicronic
bypass filters and a high efficency air filter. Ask for the specs. There are
astm standard tests that measures this performance.  I've always gone by the
creed if it is really that good they will show you why & how. Fram does not
publish the test results, except what is benifical for them (make sense of
course). But then again maybe they really do have something "new & improved"
here. 

Kris

"figures don't lie but liars can sure figure"