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Lean of peak
"...
my guess is that we are about 60F ROP ..."
Phil, That is probably one of the least desirable places you can
pick to set the mixture.
Why? Because that is a mixture setting that will guarantee that the
engine operates with the absolute highest peak cylinder pressures that it is
possible to generate for any MP and RPM you select.
We get
phone calls every day by somebody asking "Where should I set the
mixture." That takes a book to answer.
But if
you change the question - - just a little bit, to the
following: "Where should I *NOT* set the mixture then
the answer gets very much easier.
The
answer to this second question is much easier:
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A) At very high cruise power settings, set the mixture
anywhere OUTSIDE of the range from about 10-15F LOP out to 125 to 150F
ROP.
B) At
low power settings, set the mixture anywhere you want. You will not
cause some major problem, other than if you run the engine too rich, you will,
over time cause increased deposits and higher spark plug cleaning costs and you
may, eventually cause enough deposits to result in premature
maintenance.
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That
only now leaves the question as to what is HIGH and what is LOW power
settings.
For
your engine, anything over about 200 Hp probably falls into the
"high" power setting range.
There
is nothing magic about 1600F on your EGTs. 1600 is just fine. There
are some normally aspirated engines that will show 1600F EGTs during cruise.
The
*absolute* value of EGT readings on these engines is nearly immaterial - - when
looked at in isolation (in the context of other things, high EGT
values can be significant... but not necessarily harmful).
For
example, in cruise, if you turn off one mag, the EGTs will SOAR to very
high levels. Doesn't hurt anything, because the reason the EGTs go
up is that the single mag operation effectively retards
the timing and that causes the EGTs to rise - - but it also causes the peak
cylinder pressures to drop rapidly - - along with the CHTS.
The lower CHTs keep the exhaust valve cool, inspire of the higher observed EGT
values.
Regards, George
Wondering if anyone would care
to share their experiences with operation of their TSIO550E in a IVP.
We
normally operate around 18 to 20,000ft at 28inches and 2500RPM. Running ROP we
are usually set up around 1600 TIT, max EGT is around 1550 to 1560 and
fuel flow is around 21.5GPH (CHT's are around 360). We use a Vision
Microsystems engine monitoring system. Usually, indicated airspeed is around
210 and TAS around 250. My guess is that we are around 60 ROP on the first to
peak cylinder.
When we go to LOP it is fairly straight forward to get the
TIT back to 1600 but the range of EGT's is worrying...from as low as 1430 to
as high as 1570...if we lean further to try and get the highest EGT back to
around 1550 we start to run rough, so abandon and go back to ROP.
Is this a
job for balanced injectors or is there something we are missing?
Phil
Sexton
VH LLW
Melbourne Australia
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