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Newps
Guest
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 Posted: Mon Apr 30, 2007 6:12 am Post subject: Re: Fuel Flow and Peak EGT |
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Mike Noel wrote:
| Quote: | That brings up an interesting point. I think the Lycoming recommendation
previously was <75% power for unrestricted leaning. Lately I have seen <65%
as a recommendation. Anyone have any background on the two different
limits?
I've noticed in my O-360-A1A that certain RPM settings (about 2450 in my
case) get a good EGT balance on all cylinders, and aggressive leaning
produces RPM and EGT drops without engine roughness. Is this what the gami
injected engines experience running LOP?
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You have a carb, night and day difference. The key is to get all the
cylinders to peak at the same time on the same fuel flow to each
cylinder. In reality what people see is up to a .3 GPH difference
across the various cylinders. Good enough. Keep leaning and you don't
get the roughness because all the cylinders are running at the same
spot. The roughness comes from one or more cylinders essentially
missing and then really not running at all. I don't have GAMI's and I
can run very nicely LOP. |
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Denny
Guest
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| Posted: Mon Apr 30, 2007 4:50 pm Post subject: Re: Fuel Flow and Peak EGT |
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The majority of sources I have read over the years use 65% as the
maximum power at which unrestricted leaning will not burn the valves
or detonate.. It is the number I use, though with my low compression
engine I probably could go as high as 75%, but why take a chance...
And with a carb I lean aggressively... If I lean too much the engine
will start to shake like a wet dog from uneven power pulses, a smidgen
more lean and it simply shuts down...
denny |
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JGalban via AviationKB.co
Guest
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| Posted: Tue May 01, 2007 1:58 am Post subject: Re: Fuel Flow and Peak EGT |
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Mike Noel wrote:
| Quote: | That brings up an interesting point. I think the Lycoming recommendation
previously was <75% power for unrestricted leaning. Lately I have seen <65%
as a recommendation. Anyone have any background on the two different
limits?
|
Lycoming has always given recommended limitations on operations. 75% in
cruise was always the common limit for leaning. Other documents have given
lower numbers with the phrase "for maximum service life". Here's an example
from a Lycoming Key Reprint article on leaning :
8. For maximum service life, maintain the following recommended
limits for continuous cruise operation:
a. Engine power setting — 65% of rated or less.
b. Cylinder head temperatures — 400˚ F. or below.
c. Oil temperature — 165˚ F. — 220˚ F.
Available at
http://www.lycoming.com/support/tips-advice/key-reprints/pdfs/Key%20Operations.pdf
John Galban=====>N4BQ (PA28-180)
--
Message posted via AviationKB.com
http://www.aviationkb.com/Uwe/Forums.aspx/aviation/200704/1 |
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Kobra
Guest
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| Posted: Tue May 01, 2007 3:28 am Post subject: Re: Fuel Flow and Peak EGT |
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| Quote: | What model engine? I often run LOP at those settings with a Lyc. O-360
F1A6.
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I have an IO360 A1B6. I am embarrassed to say that I did not know, nor was
I ever taught, that below 65% power you could lean to peak without hurting
the engine. I have been wasting gas and money now since June of 2002. I am
really ashamed that I did not open my eyes. I just dismissed talk of LOP
and running at peak as bad advice without an engine analyzer. This is
because my instructor/A&P always said to run the engine 100 degrees ROP and
never to run LOP "because gas is cheaper than cylinders". I took his word
as gospel and have flown 75 to 100 degrees ROP ever since I bought my plane.
Even my type club said to me recently, "about 65% power and lean until your
hearts content..."
Thanks for all your help.
Kobra |
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Newps
Guest
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| Posted: Tue May 01, 2007 4:17 am Post subject: Re: Fuel Flow and Peak EGT |
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First off gas is not cheaper than cylinders so that's a dumb argument
from the get go. At 65% you want to be leaner than peak EGT or richer
than 100 ROP for best engine health. At 75% you want to be leaner than
40 LOP or richer than 180 ROP. There are other power settings with
their own combos but these are the two most used. At your stated 65%
get yourself about 15-20 LOP. That's good for the engine and the loss
of airspeed is negligible. You can go leaner but you'll start to notice
a speed loss.
Kobra wrote:
| Quote: | What model engine? I often run LOP at those settings with a Lyc. O-360
F1A6.
I have an IO360 A1B6. I am embarrassed to say that I did not know, nor was
I ever taught, that below 65% power you could lean to peak without hurting
the engine. I have been wasting gas and money now since June of 2002. I am
really ashamed that I did not open my eyes. I just dismissed talk of LOP
and running at peak as bad advice without an engine analyzer. This is
because my instructor/A&P always said to run the engine 100 degrees ROP and
never to run LOP "because gas is cheaper than cylinders". I took his word
as gospel and have flown 75 to 100 degrees ROP ever since I bought my plane.
Even my type club said to me recently, "about 65% power and lean until your
hearts content..."
Thanks for all your help.
Kobra
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robinfly@aol.com
Guest
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| Posted: Wed May 02, 2007 2:13 am Post subject: Re: Fuel Flow and Peak EGT |
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On Apr 30, 4:17 pm, Newps <nowh...@nowhere.com> wrote:
| Quote: | First off gas is not cheaper than cylinders so that's a dumb argument
from the get go. At 65% you want to be leaner than peak EGT or richer
than 100 ROP for best engine health. At 75% you want to be leaner than
40 LOP or richer than 180 ROP. There are other power settings with
their own combos but these are the two most used. At your stated 65%
get yourself about 15-20 LOP. That's good for the engine and the loss
of airspeed is negligible. You can go leaner but you'll start to notice
a speed loss.
Kobra wrote:
What model engine? I often run LOP at those settings with a Lyc. O-360
F1A6.
I have an IO360 A1B6. I am embarrassed to say that I did not know, nor was
I ever taught, that below 65% power you could lean to peak without hurting
the engine. I have been wasting gas and money now since June of 2002. I am
really ashamed that I did not open my eyes. I just dismissed talk of LOP
and running at peak as bad advice without an engine analyzer. This is
because my instructor/A&P always said to run the engine 100 degrees ROP and
never to run LOP "because gas is cheaper than cylinders". I took his word
as gospel and have flown 75 to 100 degrees ROP ever since I bought my plane.
Even my type club said to me recently, "about 65% power and lean until your
hearts content..."
Thanks for all your help.
Kobra- Hide quoted text -
- Show quoted text -
|
Do these 65% v. 75% ROP & LOP temp limits have any relation to
compression ratio of the engine? In another words, if my engine is
7:1 CR & running at 75% power, can I run at temp limits for an engine
that is 8.5:1 CR running at 65%? |
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Matt Barrow
Guest
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| Posted: Wed May 02, 2007 6:02 am Post subject: Re: Fuel Flow and Peak EGT |
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"robinfly (AT) aol (DOT) com" <rmhou (AT) yahoo (DOT) com> wrote in message
news:1178054010.708969.83110 (AT) n76g2000hsh (DOT) googlegroups.com...
| Quote: | On Apr 30, 4:17 pm, Newps <nowh...@nowhere.com> wrote:
First off gas is not cheaper than cylinders so that's a dumb argument
from the get go. At 65% you want to be leaner than peak EGT or richer
than 100 ROP for best engine health. At 75% you want to be leaner than
40 LOP or richer than 180 ROP. There are other power settings with
their own combos but these are the two most used. At your stated 65%
get yourself about 15-20 LOP. That's good for the engine and the loss
of airspeed is negligible. You can go leaner but you'll start to notice
a speed loss.
Do these 65% v. 75% ROP & LOP temp limits have any relation to
compression ratio of the engine?
|
No, not really.
| Quote: | In another words, if my engine is
7:1 CR & running at 75% power, can I run at temp limits for an engine
that is 8.5:1 CR running at 65%?
|
Run at the temp limits defined (EGT/CHT) in your POH, where ever that fall
on the LOP graph.
http://www.avweb.com/news/pelican/182084-1.html (Plus the entire engine
series defined in the sidebar on the right).
--
Matt Barrow
Performace Homes, LLC.
Colorado Springs, CO |
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