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This File was found at: http://www.eaa42.org/misc/gregs_show.ppt It has been learned that the authors of this fine piece of work are: Advanced Pilot Seminars http://www.advancedpilot.com/. Old wives tales of leaning:. EGT rises indefinitely with leaning Highest EGT shows leanest cylinder

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slide1
This File was found at: http://www.eaa42.org/misc/gregs_show.ppt
  • It has been learned that the authors of this fine piece of work are: Advanced Pilot Seminars http://www.advancedpilot.com/
old wives tales of leaning

Old wives tales of leaning:

EGT rises indefinitely with leaning

Highest EGT shows leanest cylinder

Hottest CHT is leanest cylinder

Running LOP causes high CHT

Running LOP will damage valves

Running LOP will increase cylinder wear

“Gas is cheaper than engine overhaul”

slide4
Cessna 414
  • Engines at same power !
  • Ball is centered.
  • What is going on?
slide5

75 ROP

50 LOP

what might lead to detonation
What might lead to detonation?
  • Operation of any cylinder in “The Red Box”
  • Inadequate baffling, Bird nests
  • High power at low airspeed (poor cooling)
  • Fouled fuel injector
  • Incorrect magneto timing
  • Bad fuel
  • Bad spark plug acting as a glow plug
  • Intake manifold leaks?
  • No enrichment at full throttle?
the red box defined
THE RED BOX defined:
  • At and below about 60% power, there is no red box. Put the mixture wherever feels right.
  • At ~ 65% power, avoid 100ºF ROP to Peak.
  • At ~ 70%, avoid 125ºF ROP to 25ºF LOP.
  • At ~ 75%, avoid 180ºF ROP to 40ºF LOP.
  • At ~ 80%, avoid 200ºF ROP to 60ºF LOP.
a catch to lop ops

A Catch to LOP Ops

The spread between EGT peaks will be excessive without tuned injectors (or with a carbureted engine), and the engine will run rough LOP.

Avoidance of roughness comes from tuning the injectors so they all peak within 0.5 gph

What can you do with a carbureted engine?

slide16

HP difference with

25 LOP

113 LOP

some details

Some Details

As you lean, the first cylinder to peak is the leanest, the last to peak is the richest.

If cruising ROP, you lean by the leanest cylinder, but

If cruising LOP, you lean by the richest cylinder- because you are on the other side of the Red Box.

And you need an engine analyzer to show you where all this is happening!

some basics

Absolute EGT numbers are inexact and of little value – but degrees relative to the peak EGT are extremely important in defining landmarks in combustion for each cylinder.

CHTs are important of themselves

Running ROP or LOP are valid choices, but most pilots running ROP are not running far enough ROP, and are in the “Red Box”.

SOME BASICS
when rop when lop

When ROP When LOP

Lean by leanest cylinder Lean by richest cylinder

Air flow determines power Fuel flow determines power

Extra fuel retards combustion Extra air retards combust

Carbon monoxide plentiful Minimal CO

Not most fuel efficient Fuel efficient at 20-30 LOP

Engine dirty Oil and engine stay cleaner

Engine runs hot Engine runs cooler

when lop

When LOP:

Fuel flow determines power

Engines with 7.5:1 compression put out 12.7 hp per GPH

Engines with 8.5:1 compression put out 13.9 hp per GPH

what does an engine analyzer do
What does an engine analyzer do?
  • Shows EGT and CHT of each cylinder in real time
  • Records that data every 6 seconds for later download and review
  • Presents EGT and CHT with rising bars as well as numbers
  • Lean find function shows richest and leanest cylinder as mixture is brought back
  • Alarms can be set, like:
    • Any CHT above 380F.
    • Excessive cooling rate
    • Any EGT above 1600F
slide27

Max manifold pressure

Great airspeed

Low fuel flow

It’s WOTLOPSOP!

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