From: "Tracy Crook rwstracy@gmail.com" <flyrotary@lancaironline.net>
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Date: Sun, 30 Sep 2018 11:38:21 -0600
Subject: Re: [FlyRotary] 2 pass or not 2 pass... oil cooler?
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>


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No elaborate Studies on this, just my observations over the years, so take t=
his with a grain of salt.
I think the advantages of a double pass cooler are highly over rated.  I=E2=80=
=99d use which ever worked out best for hose routing.  I also think the stoc=
k Mazda cooler is underrated.  It works much better than its appearance woul=
d suggest.

Inlets and Ducts are harder to get right than I ever suspected.  Pressure re=
adings in front and after coolers are invaluable for determining when they a=
re working. =20

Outlet ducts from the cooler exit would be great but I=E2=80=99ve never foun=
d them to be practical.  They required too much compromise with other things=
.  BUT, I reasoned that the velocity immediately out of the coolers is not t=
hat high and is turbulent, so I concentrated on the cowl outlet where the ve=
locity IS high.  Aim to make it as much like a rocket engine nozzle as possi=
ble.  I found that shaping the exit into a diffuser improved cooling a bit e=
ven though adding the pieces that shaped it reduced the throat area of the '=
nozzle'.   Avoid sharp turns, corners and edges.  Cleaning up the exit duct a=
lone got me almost 5 deg F. improvement in cooling on the RV-8. =20

Tracy Crook

> On Sep 30, 2018, at 01:55, Todd Bartrim bartrim@gmail.com <flyrotary@lanca=
ironline.net> wrote:
>=20
> Hey Rotorheads;
>    This summer I bought the Fluidyne DB30618 but it is only a single pass.=
 I recently inquired about them with Summit Racing and they say they will pr=
ovide a 2-pass as a custom order. The stock oil cooler is a 2-pass but much m=
ore restrictive. The single pass added a longer hose with a 180 swept fittin=
g to make it work.
>    I'm seeing higher temps than I'd like to despite my improved duct work.=
 Actually inlet duct was improved, but outlet duct is new as I didn't have o=
ne before and I do wonder if the outlet duct is restrictive but I'm limited w=
ith space and old nose gear mount being in the way (as much as I'd like to r=
emove the nose wheel mount it is integral to the engine mount, so I'm stuck w=
ith it), so I wonder if it would be better to remove the exit duct completel=
y and just leave the oil cooler exit air un-ducted?
>    But to the main question for tonight, I'm thinking about converting my c=
ooler to a 2-pass. I have been experiencing higher oil temps than expected a=
t around 110C and considering the OAT has dropped considerably, I would like=
 to reduce these somewhat. I suspect that the flow is not going through the e=
ntire cooler evenly with a majority of flow channeling through only a few of=
 the tubes as it is not really any different than the temps it used to see w=
ith the Mazda cooler. The larger size and more efficient design should produ=
ce better cooling if oil was flowing evenly through all tubes and spending a=
 longer time in the cooler.
>   So I'm thinking it should be simple enough to convert to a 2-pass cooler=
 which should ensure a better distribution of flow through all the tubes. Bu=
t is it really so simple?? See pic at
> https://photos.app.goo.gl/TrU99jXjftz4X8h37
> It would seem a simple matter to zip-cut a slot where the red line is, sli=
de in a baffle plate and weld it up, re-sealing the end tank, drill a hole a=
nd weld in the new AN10 fitting and at the other end, zip off the old AN12 f=
itting and weld it up. This would also simplify plumbing, as the oil in line=
 would be shorter and go straight in with no 180 bend.
>    But the thing is I can only weld on 3 sides of the baffle plate that I w=
ould install. I can ensure that it is tightly seated against the tube end pl=
ate between the tube but it wouldn't be a sealed junction. Do it right and a=
n insignificant amount of oil may bypass there and not go through the tubes.=
 Do it wrong and it could be a significant amount with a drastic reduction i=
n cooling.
>    Obviously I've already removed the cooler and brought it home with the i=
ntent to do this mod, but now I'm second guessing myself. I've considered th=
at if Summit Racing is modifying these as a custom order then they likely ar=
e doing just what I plan to do. Otherwise it would have to be done during ma=
nufacture by Fluidyne.
>    It seems simple, but I lost sleep last night considering all the variou=
s issues. Still didn't do it today, so I figured I'd pose the question to th=
e group and go hunting with my kid tomorrow while I wait for the opinions to=
 arrive.
>=20
>    On another topic, during a take-off roll the other day, the diaphragm i=
n my old stock wastegate actuator blew. I didn't catch it with the throttle u=
ntil I hit 16.5 psi of boost. No damage but I gotta say that's a fun way to g=
et off the ground in a hurry! I usually limit myself to 6 psi of boost as th=
at was the spring pressure. I do have an electronic controller (TurboSmart) w=
hich allows me to have higher pressures above the spring pressure, but that i=
s intended for high altitude and mountain flying.=20
>   I've ordered a new adjustable piston type of actuator that comes with a s=
election of 6 springs. I intend to use the 3 psi spring as I usually use the=
 boost very conservatively and the TurboSmart controller can give me more if=
 I need it for short mountain strips.
> Anyways, I look forward to your opinions on the oil cooler.
>=20
> Todd Bartrim     .......  20.6 hours on new RV9 version 2.0.....  I had to=
 cash in beer cans for gas money....
> C-FSTB
> RV9 13Bturbo

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<html><head><meta http-equiv=3D"content-type" content=3D"text/html; charset=3D=
utf-8"></head><body dir=3D"auto">No elaborate Studies on this, just my obser=
vations over the years, so take this with a grain of salt.<div>I think the a=
dvantages of a double pass cooler are highly over rated. &nbsp;I=E2=80=99d u=
se which ever worked out best for hose routing. &nbsp;I also think the stock=
 Mazda cooler is underrated. &nbsp;It works much better than its appearance w=
ould suggest.</div><div><br></div><div>Inlets and Ducts are harder to get ri=
ght than I ever suspected. &nbsp;Pressure readings in front and after cooler=
s are invaluable for determining when they are working. &nbsp;</div><div><br=
></div><div>Outlet ducts from the cooler exit would be great but I=E2=80=99v=
e never found them to be practical. &nbsp;They required too much compromise w=
ith other things. &nbsp;BUT, I reasoned that the velocity immediately out of=
 the coolers is not that high and is turbulent, so I concentrated on the cow=
l outlet where the velocity IS high. &nbsp;Aim to make it as much like a roc=
ket engine nozzle as possible. &nbsp;I found that shaping the exit into a di=
ffuser improved cooling a bit even though adding the pieces that shaped it r=
educed the throat area of the 'nozzle'. &nbsp; Avoid sharp turns, corners an=
d edges. &nbsp;Cleaning up the exit duct alone got me almost 5 deg F. improv=
ement in cooling on the RV-8. &nbsp;</div><div><br></div><div>Tracy Crook</d=
iv><div><div><br>On Sep 30, 2018, at 01:55, Todd Bartrim <a href=3D"mailto:b=
artrim@gmail.com">bartrim@gmail.com</a> &lt;<a href=3D"mailto:flyrotary@lanc=
aironline.net">flyrotary@lancaironline.net</a>&gt; wrote:<br><br></div><bloc=
kquote type=3D"cite"><div><div dir=3D"ltr"><div dir=3D"ltr"><div>Hey Rotorhe=
ads;</div><div>&nbsp; &nbsp;This summer I bought the Fluidyne DB30618 but it=
 is only a single pass. I recently inquired about them with Summit Racing an=
d they say they will provide a 2-pass as a custom order. The stock oil coole=
r is a 2-pass but much more restrictive. The single pass added a longer hose=
 with a 180 swept fitting to make it work.</div><div>&nbsp; &nbsp;I'm seeing=
 higher temps than I'd like to despite my improved duct work. Actually inlet=
 duct was improved, but outlet duct is new as I didn't have one before and I=
 do wonder if the outlet duct is restrictive but I'm limited with space and o=
ld nose gear mount being in the way (as much as I'd like to remove the nose w=
heel mount it is integral to the engine mount, so I'm stuck with it), so I w=
onder if it would be better to remove the exit duct completely and just leav=
e the oil cooler exit air un-ducted?</div><div>&nbsp; &nbsp;But to the main q=
uestion for tonight, I'm thinking about converting my cooler to a 2-pass. I h=
ave been experiencing higher oil temps than expected at around 110C and cons=
idering the OAT has dropped considerably, I would like to reduce these somew=
hat. I suspect that the flow is not going through the entire cooler evenly w=
ith a majority of flow channeling through only a few of the tubes as it is n=
ot really any different than the temps it used to see with the Mazda cooler.=
 The larger size and more efficient design should produce better cooling if o=
il was flowing evenly through all tubes and spending a longer time in the co=
oler.</div><div>&nbsp; So I'm thinking it should be simple enough to convert=
 to a 2-pass cooler which should ensure a better distribution of flow throug=
h all the tubes. But is it really so simple?? See pic at</div><div><a href=3D=
"https://photos.app.goo.gl/TrU99jXjftz4X8h37">https://photos.app.goo.gl/TrU9=
9jXjftz4X8h37</a><br></div><div>It would seem a simple matter to zip-cut a s=
lot where the red line is, slide in a baffle plate and weld it up, re-sealin=
g the end tank, drill a hole and weld in the new AN10 fitting and at the oth=
er end, zip off the old AN12 fitting and weld it up. This would also simplif=
y plumbing, as the oil in line would be shorter and go straight in with no 1=
80 bend.</div><div>&nbsp; &nbsp;But the thing is I can only weld on 3 sides o=
f the baffle plate that I would install. I can ensure that it is tightly sea=
ted against the tube end plate between the tube but it wouldn't be a sealed j=
unction. Do it right and an insignificant amount of oil may bypass there and=
 not go through the tubes. Do it wrong and it could be a significant amount w=
ith a drastic reduction in cooling.</div><div>&nbsp; &nbsp;Obviously I've al=
ready removed the cooler and brought it home with the intent to do this mod,=
 but now I'm second guessing myself. I've considered that if Summit Racing i=
s modifying these as a custom order then they likely are doing just what I p=
lan to do. Otherwise it would have to be done during manufacture by Fluidyne=
.</div><div>&nbsp; &nbsp;It seems simple, but I lost sleep last night consid=
ering all the various issues. Still didn't do it today, so I figured I'd pos=
e the question to the group and go hunting with my kid tomorrow while I wait=
 for the opinions to arrive.</div><div><br></div><div>&nbsp; &nbsp;On anothe=
r topic, during a take-off roll the other day, the diaphragm in my old stock=
 wastegate actuator blew. I didn't catch it with the throttle until I hit 16=
.5 psi of boost. No damage but I gotta say that's a fun way to get off the g=
round in a hurry! I usually limit myself to 6 psi of boost as that was the s=
pring pressure. I do have an electronic controller (TurboSmart) which allows=
 me to have higher pressures above the spring pressure, but that is intended=
 for high altitude and mountain flying.&nbsp;</div><div>&nbsp; I've ordered a=
 new adjustable piston type of actuator that comes with a selection of 6 spr=
ings. I intend to use the 3 psi spring as I usually use the boost very conse=
rvatively and the TurboSmart controller can give me more if I need it for sh=
ort mountain strips.</div><div>Anyways, I look forward to your opinions on t=
he oil cooler.</div><div><br></div><div><div dir=3D"ltr" class=3D"gmail_sign=
ature"><div dir=3D"ltr">Todd Bartrim&nbsp; &nbsp; &nbsp;.......&nbsp; 20.6 h=
ours on new RV9 version 2.0.....&nbsp; I had to cash in beer cans for gas mo=
ney....</div><div>C-FSTB</div><div>RV9 13Bturbo</div></div></div></div></div=
>
</div></blockquote></div></body></html>=

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