Item Subject: cc:Mail Text
I was coaching my 2nd/3rd grade soccer team on Saturday morning (if
you have heard that saying about managing engineers being like herding
cats, then you should try this), when I saw one of the parents, my
friend Lou, standing on the sidelines, wearing his old FRAM shirt.
That's right! He's a mechanical engineer who used to work for them.
So, in between trying to get the kids to remember their positions and
stop watching that airplane, I asked what he knew about the PH8A and
3512. "Yeah,", he replied. " I remember when we were designing that
short one....'
Anyway, here's the scoop. The PH8A has a pressure relief function
that opens if the pressure drop across the filter goes over 8 to 10
PSI. The burst pressure for the case is around 200 PSI The 3512 is
intended for higher pressure application, with a 30 to 40 PSI pressure
relief, and a case burst pressure of 400-500 PSI. This means that if
our oil pumps are delivering 50 PSI to a clogged 3512, there might be
as little as 10 PSI feeding the engine before the relief opens. (Do
our pressure gauges measure before or after the filter?) He wasn't
really concerned about typical flow rates through the 3512, and
figured that the pressure drop across them would not get very high
unless the engines were REALLY cruddy, which, of course, would never
be OUR problem, right?
And, many GM filters DON'T have bypasses, since that function is built
into the block.
Lou cautioned that these numbers may not be exact, being what he
could quickly remember from a few years back.
Stu Brennan
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