From: "Todd Bartrim" <flyrotary@lancaironline.net>
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Date: Mon, 21 Aug 2017 23:05:14 -0700
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Subject: Heat Soak & Fuel Purge valve- Another half baked idea?
To: FlyRotary <flyrotary@lancaironline.net>
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    With my improved ducting I seem to be able to withstand extensive
ground running without overheating (but, It was only 21C today), however
I've noticed that the temps really take a spike after shutdown. I measure
coolant temps out of the engine, into the Laminova exchanger, into the
engine and behind both left & right rad. What I've been seeing is the
engine temps hottest exiting the engine, cooler going back in, while
running as it should be.
   But immediately after shutdown with no airflow the temps at the left rad
(closest to turbo) starts to climb. The controller for my EWP will continue
to run pump for 5 minutes after shutdown, so the coolant seems to be
absorbing this radiant heat as the temps into the Laminova and then into
the engine begin to rise as well. The engine acts like a heat sink
absorbing this heat  Kinda backwards I figure. But not a big deal, if I
fire it up again or if I'm done for some time.
However when I went in for dinner and came back out an hour later I
couldn't get enough fuel pressure to start (max 16psi). I converted to a
returnless fuel system which seems great, however my hi-press fuel pumps
are firewall mounted rather than in-tank as a true returnless system has. I
do have low pressure Facet pumps supplying the system in a cool location,
however this wasn't enough to overcome the vapor pressure. I opened the
cowl oil hatch to vent the heat and an hour later I checked and all was
good again.
  Previously I had a small NACA duct on the belly of the cowl feeding a 2"
scat tube to cool the fuel system in flight as I had all that other hot air
swirling around in there without proper exit ducting. That duct is still
available as I only surface filled it with foam and then glassed over it,
so I could chisel that out and use it again, but I don't think that will do
much good as it would really only cool in flight and I don't think that is
a problem.
   Sorry for the long-winded preface, but here comes the half baked idea.
Instead of going back to a return type system I was thinking about a
push-button operated solenoid valve that would tee into the fuel line
before the regulator and return fuel to a main tank only while the button
is pushed. It would have to be mounted before the regulator so that it
would be able to vent hot fuel when the pumps can't reach enough pressure
to open the regulator. And because it would only open when the button is
held there would be no worries about accidentally pumping fuel overboard
through a vent from an already full tank.
  So the thought is that I fly to some airport, taxi in to get that $100
hamburger, back out an hour later, heat soak leaves me unable to get any
fuel pressure so I hold that button in for a minute while my facet pumps
move cool fuel into the system and hi-press pump starts doing it's hi-press
thing, let go of the button and start as usual.
  So is this a lousy idea, a good idea, or is this already being done and I
just missed the memo?

I welcome all comments & criticism on this. Once I haul this thing back to
the airport I really don't want to be doing any more work to it.


Todd Bartrim  --  Half baked is what I do best!

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<div dir=3D"ltr">=C2=A0 =C2=A0 With my improved ducting I seem to be able t=
o withstand extensive ground running without overheating (but, It was only =
21C today), however I&#39;ve noticed that the temps really take a spike aft=
er shutdown. I measure coolant temps out of the engine, into the Laminova e=
xchanger, into the engine and behind both left &amp; right rad. What I&#39;=
ve been seeing is the engine temps hottest exiting the engine, cooler going=
 back in, while running as it should be.<div>=C2=A0 =C2=A0But immediately a=
fter shutdown with no airflow the temps at the left rad (closest to turbo) =
starts to climb. The controller for my EWP will continue to run pump for 5 =
minutes after shutdown, so the coolant seems to be absorbing this radiant h=
eat as the temps into the Laminova and then into the engine begin to rise a=
s well. The engine acts like a heat sink absorbing this heat =C2=A0Kinda ba=
ckwards I figure. But not a big deal, if I fire it up again or if I&#39;m d=
one for some time.<div>However when I went in for dinner and came back out =
an hour later I couldn&#39;t get enough fuel pressure to start (max 16psi).=
 I converted to a returnless fuel system which seems great, however my hi-p=
ress fuel pumps are firewall mounted rather than in-tank as a true returnle=
ss system has. I do have low pressure Facet pumps supplying the system in a=
 cool location, however this wasn&#39;t enough to overcome the vapor pressu=
re. I opened the cowl oil hatch to vent the heat and an hour later I checke=
d and all was good again.</div><div>=C2=A0 Previously I had a small NACA du=
ct on the belly of the cowl feeding a 2&quot; scat tube to cool the fuel sy=
stem in flight as I had all that other hot air swirling around in there wit=
hout proper exit ducting. That duct is still available as I only surface fi=
lled it with foam and then glassed over it, so I could chisel that out and =
use it again, but I don&#39;t think that will do much good as it would real=
ly only cool in flight and I don&#39;t think that is a problem.</div><div>=
=C2=A0 =C2=A0Sorry for the long-winded preface, but here comes the half bak=
ed idea.</div><div>Instead of going back to a return type system I was thin=
king about a push-button operated solenoid valve that would tee into the fu=
el line before the regulator and return fuel to a main tank only while the =
button is pushed. It would have to be mounted before the regulator so that =
it would be able to vent hot fuel when the pumps can&#39;t reach enough pre=
ssure to open the regulator. And because it would only open when the button=
 is held there would be no worries about accidentally pumping fuel overboar=
d through a vent from an already full tank.</div><div>=C2=A0 So the thought=
 is that I fly to some airport, taxi in to get that $100 hamburger, back ou=
t an hour later, heat soak leaves me unable to get any fuel pressure so I h=
old that button in for a minute while my facet pumps move cool fuel into th=
e system and hi-press pump starts doing it&#39;s hi-press thing, let go of =
the button and start as usual.</div><div>=C2=A0 So is this a lousy idea, a =
good idea, or is this already being done and I just missed the memo?</div><=
div><br></div><div>I welcome all comments &amp; criticism on this. Once I h=
aul this thing back to the airport I really don&#39;t want to be doing any =
more work to it.=C2=A0</div><div><br></div><div><br clear=3D"all"><div><div=
 class=3D"gmail_signature" data-smartmail=3D"gmail_signature"><div dir=3D"l=
tr">Todd Bartrim =C2=A0-- =C2=A0Half baked is what I do best!</div></div></=
div>
</div></div></div>

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