lml@lancaironline.net Mailing List Archive

Kevin:

That is terribly sad.

It is obvious that whoever came up with those procedures has no understanding of F:A ratios, GAMI Spread, or the value of EGT. There is so much wrong in that short document that it's pointless to discuss it in detail. Briefly, to wit:

1) Raw EGT value is meaningless in determining F:A ratio balance. Meaningless. FF is what matters.

2) The coolest EGT at peak has nothing whatsoever to do with a cylinder being critical.

3) There is nothing magical about 65% power.

4) The suggestion that 100dF ROP at high power settings is optimal is not in harmony with any of the known science, from any source, including Lycoming.

5) Running ROP without an engine monitor is much riskier than running LOP without one. They've got that backwards.

Basically, this is a very embarrassingly erroneous document. Performance Engines should be mortified at their poor level of understanding of engine management issues.

Walter

On Mar 21, 2007, at 2:50 PM, Kevin Kossi wrote:

This is what I have from Performance Engines:

How to lean a High Performance Engine by: Performance Engines.

Climb out full rich, full power to 6,000 feet (make sure all engine parameters are within the

correct temperature tolerances).

Make sure you select a somewhat desolate area. (So you do not have to worry about traffic

that much).

Preferably pick a day with little wind at your altitude.

Engage your autopilot on a heading.

Set up for 65% or less power. Suggest: 2400 rpm at 24”

Make sure you keep a log of all this.

A. Select Cylinder #1 EGT on your engine analyzer.

B. Cut the mixture back one turn at a time and WAIT until the EGT raises to a stabilized

temperature (do not continue leaning until the temperature is stabilized). The EGT will rise and

subsequently stabilize with each turn of cut back on the mixture.

C. Continue to cut back the mixture as stated in paragraph B until you see the EGT stop

climbing and start to drop.

D. Immediately note the highest temperature attainable and corresponding fuel flow at which

Cylinder 1 stopped climbing and started descending. This cylinder has reached its highest

temperature attainable (PEAK EGT).

E. Go to full rich.

F. Select EGT cylinder #2.

G. Wait for a stabilized temperature on your EGT cylinder #2.

H. Repeat paragraphs A through E. on cylinders 2, 3, 4, 5, and 6.

Now you have established the PEAK EGT for each cylinder. Each aircraft will vary, especially

experimentals.

Now select the cylinder that peaked at the lowest temperature. This is the CRITICAL cylinder.

Let’s suppose (and this is only a supposition) that the cylinder that peaked at the lowest

temperature was cylinder #5 at 1375o degrees F.

This means:

A. Your critical cylinder is #5, and..

B. For any cruise power setting (up to 75%) the EGT should be 100o F cool of this critical cylinders

peak EGT. Given the aforementioned all other cylinders will be richer and therefore within a safe

operating margin.

C. For any higher power setting (i.e. take off), the EGT should be 150o to 200o degrees F. richer

(cooler) of peak than established for the critical cylinder. If your engine’s set up can not

achieve these temperatures you will have to change the fuel flow.

By adhering to these policies you can extend the TBO of your engine.

Performance Engines does not recommend running your engine lean of peak (LOP) if the power

setting is above 65% power. Furthermore, running LOP in excess of 65% will void your warranty.

(Lycoming engines may not be operated lean of peak per the manufacturers’

recommendations.).

Please remember that to run lean of peak your aircraft must be equipped with an engine

analyzer that has downloading capability.

Operation of a Performance Engine lean of peak without a downloadable engine analyzer will

void your warranty.

Kevin Kossi
Legacy 76%

New York

Continental IO-550-EXP

10:1 Single Lightspeed Single Slick Mag

Hartzell HC-H3YF-2UFX/FC7391D-3X.

Full feathering, counterweighted, 3 blade