I was reviewing the EDM data from some of my recent flights today and
spotted a strange anomaly in the EGT traces on one flight.  I have
attached an MS Excel file with the raw data and two graphs of the data.
In chart 1 I circled the anomaly.  In chart 2 I zoomed in on the
anomaly.  This occurred about an hour into a 2.4 hr. cross-country in
dead smooth air on a CAVU day.  I'm quite sure I did not do anything
with the engine controls or fuel system at this point in the flight.  I
was cruising on autopilot enjoying the view.  I don't remember noticing
anything unusual about the engine sounds or performance at any time
during the cruise.

Moondog,

 

What's DIF - It spiked at the same time? (fuel flow, pressure?)

 

Cyl temps dipped at the same time.

 

EGTs took a dip, then spiked, then back to trend line.  You didn't feel a cough?

 

Bat stayed the same.

 

HOw about a big bug swallowed by the induction system?  How about some krud in the throttle body? How about a fuel flow hiccup?

 

Usually these things only happen over water or at night....

 

Grayhawk