Engine Operating Tips/Rich or Lean of Peak

[JMH]

Sorry to resurrect an old thread, but I’m trying to find the best techniques for an O-2A… have a edm-760 twin installed, that lists individual temps for the cylinders.

Question#1- how should I use the individual CHT knowledge? Since it is not in the manual (using the 1985 1L-2A-1 as the POH), one instructor told me 400deg is the limit, but I cant really verify that anywhere. Should that take precedent over the typical Cylinder temp gauge which only goes up to 238, where 190 is the optimum temp? Not only for a “limit” but also for leaning and cowl flap ops… leaning on the ground will increase those CHTs, so it concerns me getting close to 400 (because of that IPs comments)

Note for #9 below, that should be 190 cylinder temp, not oil…?

Question #2- for a “normal” climb the book says to pull both RPM and HG pressure “in to the green arc” and fly 105-120 KIAS with 14gph to 5000’ decreasing to 12gph at 8000’ and 10gph at 12000’… how should I be attaining those gph? I would have assumed by leaning, but #3 below seems to counter that. Leave it at 2600 rpm, full rich and modulate throttle? There is a caution about leaning “below placard values” (@2800RPM) so it almost implies that we should lean TO those values.

I have a similar question for cruise, but I see if there is already thread for it that covers it… thanks!


1) lean, lean, and lean..... on the ground. MAX EGT or until the engines are about to quit.

2) Lean on descent. Keep engine temps up.

3) Do NOT lean on climb!

4) lean ROP or LOP to >60 ROP if necessary... depending on power.

5) Never start the engines unless you are going to fly.

6) never fly for less than 1 hr.

7) do NOT run at low power settings (<50%) for any length of time unless you lean to peak EGT! PEAK EGT!

8) Do not idle the engines for any length of time. I get my clearances and ATIS with a handheld.

9) Keep up your temps by keeping cowl flaps closed except on climb. Try and keep them up to 190 deg (oil temp).

10) Insulate rear oil tube to keep condensation down on rear engine.

If you adhere to the above rules you will NOT have any problems. I have followed these rules for many years flying Cessna products and it does make a difference..

Fresh oil is cheaper than new engines. Leaning saves fuel and eliminates carbon.

[JAG]

JMH,

question #1: I noticed that you may have two different temperature scales for your cylinder temps. 190 Celsius is 374 Fahrenheit - which is a perfect temp for your cylinder heads. Continental recommends an optimal temperature of 380 degrees F for your cylinder heads.

On your note about item 9 - yes, I think this should be cylinder head temp and not oil.

Question #2: I am not a "by the numbers guy" as that. Read John Deacon's information online (pelican's Perch on Avweb, #63 through #66) to understand more about the combustion process. This is essential reading for anyone with an injected NA engine, especially our Skymasters.

Here is a table (Attached) that I developed from researching the requirements from Cessna and Continental for my 1966 Cessna 337A.

Jeff

[mshac]

I've seen a thing or two on the internet, but I do believe this takes the cake for oldest thread ever brought back to life The OP likely had a dial-up modem connection through AOL...

[JAG]

JMH,

I just want to add a bit more of a response to your question #1.

I have my engine monitor set to give me a "yellow warning" at 400 degrees F on the cylinder head temps, and "red" at 420 degrees F. The reason I did this, is that for my aircraft (NA engine), those temperatures will ensure I have the correct mixture and that I am not doing damage to my cylinders. See also this article from John Deacon https://www.avweb.com/features_old/p...mixture-magic/ ).

Sometimes, in the heat of the summer here in Texas, I may hit 400 degrees CHT on a cylinder or two on the ground, after run-up. to get cool them off, (if this happens), I ensure I am into wind (if possible) and idle the rear engine and run the front engine up for a bit to get airflow to the rear - and this brings it down should this happen. As long as I do my run-up into wind and do the rear engine first, I have almost eliminated this event.

On Take-off, my cylinder head temps do not normally exceed 340 degrees F - I have spent a lot of time ensuring my fuel pumps are set up correctly, and I run at the top end of the fuel flow when I set them up. I rarely see cylinders going above 360 degrees in the climb for the warmest one, coolest one is around 330 degrees. In cruise, I am always closing the cowl flaps. Warmest cylinder I have experienced in cruise, leaned out, is 384 degrees.

I hope this helps give some perspective. There are a lot of opinions out there, different techniques to run your engines, and even engines having their own personality. Read the articles I indicate will really give you some understanding and help you determine how you want to run your engines.

Have fun with the new engine monitor!
Jeff

[JMH]

@JAG - thanks this is all truly helpful, I read through the pelican's perch articles and it was very informative... and very stressful at the same time! While he does a great job of breaking things down to the lowest common denominator, I find myself having to balance that with the Dash-1 and other instructors/techniques (included those listed in this thread go against some of what the articles say)... obviously there really is an art here, while we try to make it a science.

Thanks for the temps, I had heard 460 is the upper limit on these engines, while my IP insisted that 400 is the limit... glad to know that I have some more wiggle room (not that I'm using 460 as a KIO, but I have seen 410/415 immediately after T/O). It does seem that my front eng seems to get warmer then the rear, not sure if that is typical, but that seems like a good technique (run the front up to help cool the aft).

That same IP unintentionally stressed me out by continuing to cycle through the CHTs during the entire sortie (couple times each during taxi, T/O, climb, etc...) like I felt like I was seriously going to do damage if I don't continuously watch them.

I've started discussion with the mechanic about increasing the fuel flow for T/O, makes sense to try and get a little more flow to keep them cool (almost non-intuitive!). Thanks!

BTW-what is a good fuel flow setting, say at 0 MSL? the Dash-1 doesn't really address it (not that I've found). Is there a # in POH?

[Jerry De Santis]

The subject of ROP or LOP is a deep one. I alway fly ROP, having said that, my intent is not to engage in this discussion other than to say it has been such a long time since I correspondent with You ERINE and you BOB COOK! It was very nice seeing you guys still very active. Good to hear from both of you! Take care my friends!

[JAG]

JMH,

Glad I am able to give you a different perspective and be helpful. I agree with your statement of making this art, into a science...Ha Ha. There is certainly a lot of information out there. I am a mechanic and a pilot (Father was as well), so I tend to look at things through different lenses - always wanting to manage my aircraft and engines in a manner that ensures reliability and performance are well balanced.

On your question about best FF at 0' MSL, follow the procedure using the Continental Motors SID97-3G. That is what your mechanic should use as the procedure when setting up the fuel pumps and making sure your injection system is working in top shape. The fuel flow data for my engines were found in the IO360 Maintenance and Overhaul Manual (M7), Table 6-3. That table shows the engine operating limits, including the metered and unmetered fuel pressures. Depending on a number of things (shown in the SID), your metered pressure should be around 15.8 to 18.2 psi. I have mine set at the high end of the scale when I set mine up, based on my static RPM corrections.

On my aircraft (337A) there is a placard that depicts I should have "Maximum Power Mixture Settings of 17.0 Gal/hr at Sea Level , 15.0 @4000', 13.0 @ 8000' and 11.0 @ 12000'". When I go to full takeoff power at SL (I am based in South Texas), my fuel flow gauge indicates closer to 18 gph, which is true to the pressures I have them set at (roughly 17.8 psi). I have set of calibrated digital gauges I use to set the fuel pumps up. I recently took my FF gauge to an overhaul shop and they tested it as well to ensure its accuracy and smoothness at all settings.

I hope this helps!
Jeff