Fuel Flow and Peak EGT

" 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

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