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.

"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

"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?

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)

"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...raph-basic.gif

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.

"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.