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Date: Sun, 29 Aug 2010 18:34:18 -0700
Message-ID: <AANLkTinVzGmiDtVBgq+0rTOxAKDxfw_f=vQv1rovrgjD@mail.gmail.com>
Subject: Lean Operation and new Turbo installation
From: David Leonard <wdleonard@gmail.com>
To: Rotary Engine <rotaryeng@earthlink.net>, 
	Rotary motors in aircraft <flyrotary@lancaironline.net>
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Well, I am pleased to report that my turbo, stock housing with TO4 wheel and
60-1 compressor with a fixed open waste gate has lasted over 230 hrs without
a single problem.  The solution to good enough?  Make it better.  I just
finished my annual during which I upgraded my turbo to a similar TO4 big
shaft wheel, but now it has a TO4E 50-trim compressor and the wastegate
flapper and actuator are back in place.  Why the change?  Either I am a
glutton for punishment or I am starting to pin down this turbo issue.  For
those of you not familiar with my turbo history, here is a quick recap:
First turbo - the stock second generation with waste gate flapper
installed, ridden hard and put away wet...  it was run at full throttle at
high altitudes, often at peak EGT.  It lasted 70 hrs before the turbine
wheel fell apart and broke off.  The thought at the time was that the stock
turbo was just too small for this heavy duty abuse and was overspeeding at
altitude.
Second turbo - small shaft TO4 wheel with 60-1 compressor and removed waste
gate flapper.  It was also run mostly at peak EGT but the power produced was
somewhat lower because of the bypassed exhaust.  It lasted about 140 hrs
until it suffered the same fate as the first turbo while I was in a long
full power decent (read extra high RPM and EGT's).  My thinking at this
point is that the high EGT's are primarily the problem.
Third Turbo - The one I just removed after 230 hrs.  Same configuration as
the second but I kept the EGT's under 1600, mostly as lean as I could while
keeping the engine running not too rough.  It was also run at pretty low
pressure ratios.  It could only make about 38" MAP on take off and about 40"
at full bore down lot.  At 16k altitude it was down to about 22".  My
curiosity now is weather I can perhaps increase the boost and continue to
have the turbo last, as long as I keep the EGT's under 1600.  I know,
glutton for punishment...

Other issues..

Lean of Peak operation.  During the turbo change I discovered that my stock
cast iron exhaust manifold had developed a number of serious cracks and some
advanced erosion.  Much of the erosion/oxidation was near the mating surface
with the turbo and it had started a small leak.  My concern is that all
those hours of LOP operation allows too much oxygen into the exhaust to
promote to oxidation and accelerates the problem.  The question is, should I
start running rich of peak to prevent rusting away the exhaust system
components?  ROP operations also allow me to keep even lower EGT's (for the
turbo) and smoother engine running (for the wife).  Turbos and exhaust
components that I get from cars usually have the appearance of being run
rich, rather than the dry orange color of the inside of my components.  The
only obvious downside is the obvious much increased fuel usage.  I think
that for the next couple hundred hours I have going to have to bite the
bullet and fly ROP (while at higher power settings).  Thoughts?

S.A.G. is really baffling.  Spark plugs only seem to be lasting 20-30 hrs
before SAG starts kicking in.  Noted by a distinct and marked loss of power
as I cross through about 1500' AGL after take off.  The problem is usually
intermittent and mildish at first becoming more consistent and remarkable as
the hours accumulate on the spark plugs.  The problem is always solved by
changing out the spark plugs.  I am switching to colder platinum plugs in
order to try to get them to last longer.  Perhaps running ROP will help them
last long too?

Time for a new Prop?  On a test flight yesterday, the engine was running
great.  No SAG.  At 7000' and 33"MAP I was at 6500 RPM, about 1/3 throttle
and doing 175KTAS.  It is a 64lengthx77pitch 3-blade Cato, but that is more
like an effective pitch of closer to 71".  I seem to remember being able to
get closer to 185KTAS at 6500 RPM in the past on the same prop but I did
have a little taken off because of the low output of the previous turbo.
After some more experience I may discover that it is time for another new
prop.  Might soon contact Paul Lipps, I liked his article in the last issue
of Contact! mag.  If that is my worst problem, I am going to be pretty
happy.

Doing some formation flying with the guys next week that may make its way
into a movie...

Keep building!
-- 
David Leonard

Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.net
http://RotaryRoster.net

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<div>Well, I am pleased to report that my turbo, stock housing with TO4 whe=
el and 60-1 compressor with a fixed open waste gate has lasted over 230 hrs=
 without a single problem.=A0 The solution to good enough?=A0 Make it bette=
r.=A0 I just finished my annual during which I upgraded my turbo to a simil=
ar TO4 big shaft wheel, but now it has a TO4E 50-trim compressor and the wa=
stegate flapper and actuator are back in place.=A0 Why the change?=A0 Eithe=
r I am a glutton for punishment or I am starting to pin down this turbo iss=
ue.=A0 For those of you not familiar with my turbo history, here is a quick=
 recap:</div>

<div>First turbo - the stock second generation=A0with waste gate flapper in=
stalled,=A0ridden hard and put away wet...=A0 it was run at full throttle a=
t high altitudes, often at peak EGT.=A0 It lasted 70 hrs before the turbine=
 wheel fell apart and broke off.=A0 The thought at the time was that the st=
ock turbo was just too small for this heavy duty abuse and was overspeeding=
 at altitude.</div>

<div>Second turbo - small shaft TO4 wheel with 60-1 compressor and removed =
waste gate flapper.=A0 It was also run mostly at peak EGT but the power pro=
duced was somewhat lower because of the bypassed exhaust.=A0 It lasted abou=
t 140 hrs until it suffered the same fate as the first turbo while I was in=
 a long full power decent (read extra high RPM and EGT&#39;s).=A0 My thinki=
ng at this point is that the high EGT&#39;s are primarily the problem.</div=
>

<div>Third Turbo - The one I just removed after 230 hrs. =A0Same configurat=
ion as the second but I kept the EGT&#39;s under 1600, mostly as lean as I =
could while keeping the engine running not too rough.=A0 It was also run at=
 pretty low pressure ratios.=A0 It could=A0only make about 38&quot; MAP on =
take off and about 40&quot; at full bore down lot.=A0 At 16k altitude it wa=
s down to about 22&quot;.=A0=A0My curiosity now is weather I can=A0perhaps =
increase the boost and continue to have the turbo last, as long as I keep t=
he EGT&#39;s under 1600.=A0 I know, glutton for punishment...</div>

<div>=A0</div>
<div>Other issues..</div>
<div>=A0</div>
<div>Lean of Peak operation.=A0 During the turbo change I discovered that m=
y stock cast iron exhaust manifold had developed a number of serious cracks=
 and=A0some advanced erosion.=A0 Much of the erosion/oxidation was near the=
 mating surface with the turbo and it had started a small leak.=A0 My conce=
rn is that all those hours of LOP operation allows too much oxygen into the=
 exhaust to promote to oxidation and accelerates the problem.=A0 The questi=
on is, should I start running rich of peak to prevent rusting away the exha=
ust system components?=A0 ROP operations also allow me to keep even lower E=
GT&#39;s (for the turbo) and=A0smoother engine running (for the wife).=A0 T=
urbos and exhaust components that I get from cars usually have the appearan=
ce of being run rich, rather than the dry orange color of the inside of my =
components.=A0 The only obvious downside is the obvious much increased fuel=
 usage.=A0 I think that for the next couple hundred hours I have going to h=
ave to bite the bullet and fly ROP (while at higher power settings).=A0 Tho=
ughts?</div>

<div>=A0</div>
<div>S.A.G. is really baffling.=A0 Spark plugs only seem to be lasting 20-3=
0 hrs before SAG starts kicking in.=A0 Noted by a distinct and marked loss =
of power as I cross through about 1500&#39; AGL after take off.=A0 The prob=
lem is usually intermittent and mildish at first becoming more consistent a=
nd remarkable as the hours accumulate on the spark plugs.=A0 The problem is=
 always solved by changing out the spark plugs.=A0 I am switching to colder=
=A0platinum plugs in order to try to get them to last longer.=A0 Perhaps ru=
nning ROP will help them last long too?</div>

<div>=A0</div>
<div>Time for a new Prop?=A0 On a test flight yesterday, the engine was run=
ning great.=A0 No SAG.=A0 At 7000&#39; and 33&quot;MAP I was at 6500 RPM,=
=A0about 1/3 throttle and doing 175KTAS.=A0 It is a 64lengthx77pitch 3-blad=
e Cato, but that is more like an effective pitch of closer to 71&quot;.=A0 =
I seem to remember being able to get closer to 185KTAS at 6500 RPM in the p=
ast on the same prop but I did have a little taken off because of the low o=
utput of the previous turbo.=A0 After some more experience I may discover t=
hat it is time for another new prop.=A0 Might soon contact Paul Lipps, I li=
ked his article in the last issue of Contact! mag.=A0 If that is my worst p=
roblem, I am going to be pretty happy.</div>

<div>=A0</div>
<div>Doing some formation flying with the guys next week that may make its =
way into a movie...</div>
<div>=A0</div>
<div>Keep building!<br>-- <br>David Leonard<br><br>Turbo Rotary RV-6 N4VY<b=
r><a href=3D"http://N4VY.RotaryRoster.net">http://N4VY.RotaryRoster.net</a>=
<br><a href=3D"http://RotaryRoster.net">http://RotaryRoster.net</a><br></di=
v>

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