Leaning to Hotest Cylinder

[O. Sami Saydjari]

My understanding is that one should lean using the "hotest" cylinder as
the reference point for peak EGT. My question is on the interpretation
of "hotest." Does that mean the cylinder that reaches the hotest EGTs
or CHTs? On mine, they are inversely related (the hotest EGTs are on
the coldest CHT cylinders).

-Sami
N2057M, Piper Turbo Arrow III

[Robert M. Gary]

The cylinder that reaches peak EGT first (not necessarily the highest
EGT temp). In other words, the EGT that starts to cool first as you are
leaning. If you have a good engine monitor, it will compute this for
you and flash the EGT on the monitor.

-Robert

[Thomas Borchert]

O.,

> Does that mean the cylinder that reaches the hotest EGTs
> or CHTs? On mine, they are inversely related (the hotest EGTs are on
> the coldest CHT cylinders).
>

Absolute temperatures are not important. The key issue is the first
cylinder to reach peak EGT. If the peak EGT for that cylinder happens to
be 200 F lower than the peak EGT of the next cylinder, that's not
important for the leaning process (although you might want to check the
engine baffling).

--
Thomas Borchert (EDDH)

[Thomas Borchert]

Aaron,

> Don't forget that O. is flying a turbo. While the absolute value of EGT isn't
> terribly important, TIT is, and it's related to EGT (of course).
>

Missed that, thanks.

--
Thomas Borchert (EDDH)

[CriticalMass]

O. Sami Saydjari wrote:
> My understanding is that one should lean using the "hotest" cylinder as
> the reference point for peak EGT. My question is on the interpretation
> of "hotest."

As others have stated in other words, the proper procedure is not to
lean to the "hottest" cylinder, but to lean to the "leanest" cylinder.

IOW, look for the first one to peak, and lean to that one. The fact
that the leanest cylinder may not be the one with the highest EGT is not
a consideration for leaning.

Note also that the leanest cylinder will vary over time. It won't
always be the same cylinder on every flight.