Fuel Flow and Peak EGT

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

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.

"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?

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.

"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?

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.

"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

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

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

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%?