REFLECTOR:M-20 Oil/Air separator

[John Dibble]

Without a PCV, piston travel causes a rapid flow of air back and forth in the breather
line.  The multiple pistons cancel this effect somewhat, but not totally.  A PCV
provides just enough resistance to prevent the back and forth flow (instead the
crankcase pressure rapdily fluctuates from positive to negative) while still allowing
air to escape as the air expands as the engine warms up.  The escaping air is fed to
the manifold inlet, but I don't believe the manifold pulls a vacuum on the crankcase.
Of course, none of this applies to aircraft engines which, fortunately, aren't
required to have the PCV emission control device.

Wayne wrote:

> Hmm I thought manifold vacuum put a slight negative pressure on the
> crankcase.
> I know the hardcore racers sometimes put a vacuum pump on the crankcase to
> insure ring seating.
> ----- Original Message -----
> From: "John Dibble" <aminetech@bluefrog.com>
> To: <reflector@tvbf.org>
> Sent: Saturday, April 03, 2004 10:30 AM
> Subject: Re: REFLECTOR:M-20 Oil/Air separator
>
> > Keith,
> > How does a PCV in the return line prevent oil loss through the
> > breather?  My breather hose is connected to an aluminum box, is that the
> > separator?  Mine has a drain plug and I am considering installing a tiny
> > return line that will drain after the engine is off, but hopefully not
> > during operation.
> > John
> >
> > KeithHallsten wrote:
> >
> > >  John, The proposal is to put the PCV valve in the return line from
> > > the separator to the engine.  There is no way that such an
> > > installation could pressurize the crankcase!  The breather tube is
> > > still the breather tube. Keith
> >
> >
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