Fuel Flow and Peak EGT

[Kobra]

Flyers,

While flying to FL from NJ last week I did what I always do and fly ROP by
75 to 100 degrees. This is how I was trained and my CFII is also my A&P /
IA.

I know enough about LOP to know I will not operate LOP without an engine
analyzer and probably GAMI injectors which I do not yet possess.

During the trip I was looking at my fuel computer and seeing an average FF
of 10.5 to 11.5 GPH at 6 to 7 thousand feet at about 22 to 23 inches MP and
2400 RPM at 75 degrees ROP.

I pulled my POH out and looked up the cruise performance numbers for those
parameters and those altitudes and I saw the recommended FF's. If I leaned
to the recommended FF's I was usually at peak EGT.

So my question is: Does Cessna advocate running at peak EGT in cruise? Or
if "advocate" is a strong word, are they at least saying "you can if you
want to" run at peak EGT in cruise? I've always heard that running at peak
EGT is bad for the top end of the engine.

Kobra

[Newps]

Kobra wrote:

> Flyers,
>
> While flying to FL from NJ last week I did what I always do and fly ROP by
> 75 to 100 degrees. This is how I was trained and my CFII is also my A&P /
> IA.

Ouch, ouch and double ouch. About the worst place to operate an engine.



>
> I know enough about LOP to know I will not operate LOP without an engine
> analyzer and probably GAMI injectors which I do not yet possess.

Neither is necessary. I have neither in my Bo, just a regular single
point EGT. Mine runs great LOP. Yours may not without the GAMI's.
Remember anything at 65% and less power it doesn't matter where you put
the mixture, you cannot harm the engine.



>
> During the trip I was looking at my fuel computer and seeing an average FF
> of 10.5 to 11.5 GPH at 6 to 7 thousand feet at about 22 to 23 inches MP and
> 2400 RPM at 75 degrees ROP.
>
> I pulled my POH out and looked up the cruise performance numbers for those
> parameters and those altitudes and I saw the recommended FF's. If I leaned
> to the recommended FF's I was usually at peak EGT.
>
> So my question is: Does Cessna advocate running at peak EGT in cruise? Or
> if "advocate" is a strong word, are they at least saying "you can if you
> want to" run at peak EGT in cruise? I've always heard that running at peak
> EGT is bad for the top end of the engine.


Do a Google search for Red Box.

[Dan Luke]

"Kobra" wrote:

> While flying to FL from NJ last week I did what I always do and fly ROP by
> 75 to 100 degrees. This is how I was trained and my CFII is also my A&P /
> IA.
>
> I know enough about LOP to know I will not operate LOP without an engine
> analyzer and probably GAMI injectors which I do not yet possess.

You are wise to err on the side of caution, but it is possible to run LOP
without fear of damaging the engine if you limit power. At 65% or below, it
can be done safely without an analyzer.

> During the trip I was looking at my fuel computer and seeing an average FF
> of 10.5 to 11.5 GPH at 6 to 7 thousand feet at about 22 to 23 inches MP and
> 2400 RPM at 75 degrees ROP.

What model engine? I often run LOP at those settings with a Lyc. O-360 F1A6.

> I pulled my POH out and looked up the cruise performance numbers for those
> parameters and those altitudes and I saw the recommended FF's. If I leaned
> to the recommended FF's I was usually at peak EGT.
>
> So my question is: Does Cessna advocate running at peak EGT in cruise? Or
> if "advocate" is a strong word, are they at least saying "you can if you
> want to" run at peak EGT in cruise? I've always heard that running at peak
> EGT is bad for the top end of the engine.

Depends on the % power you're making.

--
Dan
C172RG at BFM

[Stan Prevost]

"Newps" > wrote in message
...
>
>
> Neither is necessary. I have neither in my Bo, just a regular single
> point EGT. Mine runs great LOP. Yours may not without the GAMI's.

How do you know you are LOP on all cylinders?

[Thomas Borchert]

Kobra,

> Does Cessna advocate running at peak EGT in cruise?

Absolutely. That's what they call "best economy" setting, as opposed to "best
power", which is 75 or so ROP.

> I've always heard that running at peak
> EGT is bad for the top end of the engine.

Have you, now? And the person(s) saying that have provided proof, numbers or
at least some kind of reasoning, I assume? Which goes how?

Don't fall for OWTs. The proper reaction to statements like that above is
"Show me the numbers!". If they can't, well, they're out. The LOP people can.

--
Thomas Borchert (EDDH)

[Matt Barrow[_4_]]

"Kobra" > wrote in message
. ..
> Flyers,
>
> While flying to FL from NJ last week I did what I always do and fly ROP by
> 75 to 100 degrees. This is how I was trained and my CFII is also my A&P /
> IA.
>
> I know enough about LOP to know I will not operate LOP without an engine
> analyzer and probably GAMI injectors which I do not yet possess.

If you keep running in that area (ROP) you might not have your engine long
enough to get those things.

How much would GAMIjectors and a Engine Analyzer cost compared to a top
overhaul (or worse)?

>
> During the trip I was looking at my fuel computer and seeing an average FF
> of 10.5 to 11.5 GPH at 6 to 7 thousand feet at about 22 to 23 inches MP
> and 2400 RPM at 75 degrees ROP.

Why did you (if it WAS you) install a fuel computer but not an engine
analyzer? A fuel computer is _nice_, but only if you fly your tanks close to
empty, but an EA is a _necessity_. A $3500 EA does wonders to protect a
$20K+ engine.


>
> I pulled my POH out and looked up the cruise performance numbers for those
> parameters and those altitudes and I saw the recommended FF's. If I
> leaned to the recommended FF's I was usually at peak EGT.

http://www.avweb.com/newspics/194816_mixture_setting_triangle_graph-basic.gif

[Newps]

Stan Prevost wrote:

> "Newps" > wrote in message
> ...
>
>>
>>Neither is necessary. I have neither in my Bo, just a regular single
>>point EGT. Mine runs great LOP. Yours may not without the GAMI's.
>
>
> How do you know you are LOP on all cylinders?


I don't. Not necessary.

[Matt Barrow[_4_]]

"Newps" > wrote in message
. ..
>
>
> Stan Prevost wrote:
>
>> "Newps" > wrote in message
>> ...
>>
>>>
>>>Neither is necessary. I have neither in my Bo, just a regular single
>>>point EGT. Mine runs great LOP. Yours may not without the GAMI's.
>>
>>
>> How do you know you are LOP on all cylinders?
>
>
> I don't. Not necessary.
>
Not necessary if you don't mind burning up one or two jugs?

[Newps]

Matt Barrow wrote:

> "Newps" > wrote in message
> . ..
>
>>
>>Stan Prevost wrote:
>>
>>
>>>"Newps" > wrote in message
...
>>>
>>>
>>>>Neither is necessary. I have neither in my Bo, just a regular single
>>>>point EGT. Mine runs great LOP. Yours may not without the GAMI's.
>>>
>>>
>>>How do you know you are LOP on all cylinders?
>>
>>
>>I don't. Not necessary.
>>
>
> Not necessary if you don't mind burning up one or two jugs?


No such thing will happen.

[Matt Barrow[_4_]]

"Newps" > wrote in message
. ..
>
>
> Matt Barrow wrote:
>
>> "Newps" > wrote in message
>> . ..
>>
>>>
>>>Stan Prevost wrote:
>>>
>>>
>>>>"Newps" > wrote in message
...
>>>>
>>>>
>>>>>Neither is necessary. I have neither in my Bo, just a regular single
>>>>>point EGT. Mine runs great LOP. Yours may not without the GAMI's.
>>>>
>>>>
>>>>How do you know you are LOP on all cylinders?
>>>
>>>
>>>I don't. Not necessary.
>>>
>>
>> Not necessary if you don't mind burning up one or two jugs?
>
>
> No such thing will happen.

It will if the leanest is LOP, but one is still ROP.

[Newps]

Matt Barrow wrote:

>>No such thing will happen.
>
>
> It will if the leanest is LOP, but one is still ROP.
>


I don't do that.

[Thomas Borchert]

Matt,

> It will if the leanest is LOP, but one is still ROP.
>

And the problem with that, at 75 percent or less power, is exactly
what?

--
Thomas Borchert (EDDH)

[Matt Barrow[_4_]]

"Newps" > wrote in message
. ..
>
>
> Matt Barrow wrote:
>
>>>No such thing will happen.
>>
>>
>> It will if the leanest is LOP, but one is still ROP.
>
>
> I don't do that.

How do you know?

Isn't that the point of a temp sensor on each and every cylinder?

[Newps]

Matt Barrow wrote:
> "Newps" > wrote in message
> . ..
>
>>
>>Matt Barrow wrote:
>>
>>
>>>>No such thing will happen.
>>>
>>>
>>>It will if the leanest is LOP, but one is still ROP.
>>
>>
>>I don't do that.
>
>
> How do you know?
>
> Isn't that the point of a temp sensor on each and every cylinder?



One of the reasons, yes. But at 75% or less you don't use it for that.

[Mike Noel]

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?

--
Best Regards,
Mike

http://photoshow.comcast.net/mikenoel

Macintosh - We might not get everything right, but at least we knew the
century was going to end.

"Newps" > wrote in message
. ..
>
>
> Matt Barrow wrote:
>> "Newps" > wrote in message
>> . ..
>>
>>>
>>>Matt Barrow wrote:
>>>
>>>
>>>>>No such thing will happen.
>>>>
>>>>
>>>>It will if the leanest is LOP, but one is still ROP.
>>>
>>>
>>>I don't do that.
>>
>>
>> How do you know?
>>
>> Isn't that the point of a temp sensor on each and every cylinder?
>
>
>
> One of the reasons, yes. But at 75% or less you don't use it for that.

[Newps]

Mike Noel wrote:

> 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?




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.

[Denny]

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

[JGalban via AviationKB.com]

Mike Noel wrote:
>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

[Kobra]

> 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

[Newps]

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
>
>

[[email protected]]

On Apr 30, 4:17 pm, Newps > 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.
>
>
>
> 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%?

[Matt Barrow[_4_]]

" > wrote in message
ups.com...
> On Apr 30, 4:17 pm, Newps > 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.

> 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