> > > > You don't suppose doing away with the pressure control valve

caused

Chuck Harberts oil cooler to fail  and caused his in-flight

fire

do

you?

I'm quite certain that Chuck had made no such mod.  There were other
contributing factors, and since he had three oil coolers in series;

the

other two in the nose of the Velocity, I was guessing that the

pressure

in

the first (the one that ruptured) was running at or near whatever

the

bypass

relief is set for.

I was told (at some point) that the reason for the Oil

controller

valve

(which releases at around 150psi) was to provide a safety

release

should

the

oil cooler or filter be clogged and prevent those components

from

bursting

under the resulting high oil pressure.  The normal oil pressure

regulator is

for the routine regulation of oil pressure under normal

conditions.

Ed Anderson

We need to devise a pressure test where we can check the operation

of

that

valve. I think we can plug tap a front cover right where the

problem

O-ring

is normally located. Pump it up with a hand hydraulic pump through
the oil cooler outlet fitting on the front of the cover. Then

measure

the point where the spring releases the pressure increase.

Good idea.  I have asked three others what that bypass pressure is

and

got

three different answers; all of which were best guesses; and all

were

lower

than 150#.

And is it the same for a 20B and 13B?

Al Gietzen

Al,
On the 93+ FD engines that front housing bottom valve (called by Mazda
an Oil Pressure Control Valve) is set to relieve at 156 psi. The other
valve, called a Regulator Valve has a relief pressure of 110 psi (this
is the one mounted on the bottom corner of the rear housing, and lets
oil back into pan). The oil cooler valve relieves at a pressure
differential of 50 psi, and the oil filter is supposed to relieve at 14
psi differential.

You can find these values in your workshop manual in the lubrication
section. The 20B is anybody's guess. I have found NO ONE able to get a
20B workshop manual that is readable. (Hint to Australian and NZ
readers-got one?)
[Marc Wiese]

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