More About Leaning During Climb

"John" wrote:
So, what is magic about the 1350 degree sea-level full rich takeoff
temp? Can anyone suggest any good reasons why it is not equally safe
to lean to operate at the 1450 degree conditon during climb?

The EGT isn't what matters; it's the CHT's that are important. As long as
they don't get too high, go ahead and lean as you climb. I have an engine
analyzer that I watch while I climb, using whatever mixture setting I need
to keep the hottest cylinder below 400 deg, F.

If 1450
degrees is good for hours and hours of continuous operation at cruise,
and if cylinder temps are green, why needlessly expend more scarce
fossil fuel operating at 1350 degrees?

No reason at all, IMO.

Won't the engine also develop
more power at 1450 degrees than at 1350, which seems quite worthwhile
for a number of reasons?

Yep.

I'm not trying to be contentious, just
wondering if anyone has ideas about it that I haven't considered.

I think you've got it covered.
--
Dan
C172RG at BFM

wrote in news:beeeb3$13o$1
@solaris.cc.vt.edu:

What do you (or anyone else for that matter) think?

Sounds quite reasonable.

The idea of leaning during climb is to keep the mixture about the same,
and the temps in a good operating range - all of which it seems you are
doing.

Max power is about 100 ROP. That is a point where there is still excess
fuel to vaporize for added cylinder pressure, while at the same time
providing cooling. Lots of power, but it wastes fuel and is not a very
clean burn. Contrary to the original post, higher EGT's does NOT equate
to more power - often the contrary. From Best Power the power actually
declines as you approach peak EGT. This point gives you hotest exhaust
gasses (there are some technicalities here I won't bother with at the
moment), and best economy. LOP, we go further down the power curve
(which we can make up for if we still have more throttle available), and
start cooling with excess air instead of excess fuel. Exhaust is
cleanest.

Critical thing to watch is your CHT's. You are dead on as for keeping
them below 400, and lower would be better but may not be an option in
the climb. Technically EGT's on that Seneca can get to 1650 - but any
EGT measurement is guesswork at best and I prefer not to push it.

Look for CHT's down around 400 in the climb, and 350 in cruise, and you
will be in good shape.


-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
-----------------------------------------------

On 7 Jul 2003 15:24:37 -0700, (John) wrote:

The recent Avweb article on leaning recommends leaning during climb to
maintain the same EGT as one sees during a full rich takeoff from sea

snip

Are we talking NA Lycoming Seneca, or TS TCM Seneca?

I would respectively suggest doing a Google groups search on leaning,
then sign up for free Avweb and read all the Deakin dude
correspondence.

A lot of this has been covered before in the 'groups.

FWIW, 50 degrees ROP is generally considered not the best place to
cruise. Definitely wouldn't use it in the climb.

regards;

TC