Help! Manifold Pressure/Leaning inconsistencies.

[MarinMooney]

I need help!

I am trying to be a conscientious as I can when running the O-360 on my 1963 M20C.  I have been on forums, and read as many articles as I can find.  The series of articles by John Deakin was very informative and technical.

Based on the graphs in John's articles, he advocates adhering to a CHT limit of 400F.  But he contends that each of the cylinders will read differently, so since I only have one gauge, it is very inaccurate.

Additionally, he discusses leaning procedures, and contends that 50 LOP is about the worst place to run an engine.  50 LOP is exactly where some of the documentation I have read says to run the engine.

John's articles are from 1999, and I assume there is some new thinking on how to run the O-360 from an economical standpoint, a power standpoint, and a wear and tear standpoint.

I know I have spanned quite a few topics, but does anyone have either a concise explanation of the current logic on MP, RPM and leaning procedures?  Alternatively, if there is a document that spells out the procedures, I would love to read it.

I am wondering if I am out of luck having just one CHT and EGT gauge.  Maybe it is time to invest in individual cylinder gauges!

Thanks,

Steve

[Bob_Belville]

Steve, I doubt that you're able to run your O-360 50 LOP (lean of peak). Do you mean 50 Rich of Peak? The prevailing wisdom is that it is tough to run a carburetor engine LOP. 

If you're on a tight budget or have other priorities you might look into a used multi-cylinder engine monitor. People here and elsewhere are upgrading their EDMs to primary instruments like the JPI EDM 930 and are selling perfectly good edm 700s etc. 

There should be dozens of threads here on power settings and leaning M20Cs. Try the search function.

[cctsurf]

I asked this question a while back, and yes, the manual in my '62 M20C does say that we should be flying at 50 LOP...  I don't fly it there, but that is what it recommends.

[Marauder]

There are a number of options available for engine analyzers including those removed by owners for upgrades. You really need to have full visibility to the CHT and EGTs to do any leaning. I find that a couple of my cylinders take turns being the first to be leanest and neither are #3 where the factory EGT was installed.

Sent from my iPad using Tapatalk

[Bob_Belville]

10 minutes ago, cctsurf said:

I asked this question a while back, and yes, the manual in my '62 M20C does say that we should be flying at 50 LOP...  I don't fly it there, but that is what it recommends.

Interesting. I have an Owner's manual for a '66C. It calls for best economy as 25 deg LOP and best power as 100 ROP.  It also warns not to lean at all at 75% power or more. 

And the manual for my '66E calls for 25 ROP for best economy. 

[cctsurf]

Sorry, it's 25 LOP...  I looked it up on here:  http://mooneyspace.com/topic/13065-manual-specifies-o-360-lop/

 

[Bob_Belville]

This is a must read: 

http://www.avweb.com/news/savvyaviator/savvy_aviator_59_egt_cht_and_leaning-198162-1.html

 

[par]

1 hour ago, MarinMooney said:

I need help!

I am trying to be a conscientious as I can when running the O-360 on my 1963 M20C.  I have been on forums, and read as many articles as I can find.  The series of articles by John Deakin was very informative and technical.

Based on the graphs in John's articles, he advocates adhering to a CHT limit of 400F.  But he contends that each of the cylinders will read differently, so since I only have one gauge, it is very inaccurate.

Additionally, he discusses leaning procedures, and contends that 50 LOP is about the worst place to run an engine.  50 LOP is exactly where some of the documentation I have read says to run the engine.

John's articles are from 1999, and I assume there is some new thinking on how to run the O-360 from an economical standpoint, a power standpoint, and a wear and tear standpoint.

I know I have spanned quite a few topics, but does anyone have either a concise explanation of the current logic on MP, RPM and leaning procedures?  Alternatively, if there is a document that spells out the procedures, I would love to read it.

I am wondering if I am out of luck having just one CHT and EGT gauge.  Maybe it is time to invest in individual cylinder gauges!

Thanks,

Steve

You are in luck my friend because I also own a 63c and had similar questions before I decided to go ahead and install an EDM-830. From my limited experience, I have learned the following (I run WOT/2400rpm in cruise with a 3-blade prop):

-First, you can pretty much forget about keeping your CHT's below 400 on at least the #3 cylinder if not on more during T/O and climb out. My 50 year old mooney gauge used to show close to 500 at times, which was the original reason I installed the 830. It turns out the stock gauge was incorrect but I regularly see CHT's above 400 on 2,3, and 4 during climb out. After speaking with several mechanics to include Don Maxwell (Mooney guru), no one really seemed all that concerned with this fact. My recommendation to you is to stop worrying about it because there is no 100% solution to this issue with our plane. It does appear to be a common complaint though. 

-As far as LOP/ROP goes, you can see the picture posted below that shows my average fuel flow of 7.5gph during my last flight at 9k. This is certainly LOP operation and my CHT's are very happy at this setting. I would not attempt this without the EDM-830 but for your information, my procedure is as follows: After leveling off, lean until roughness, richen it up until it goes away and then lean very slowly to accept a very minor amount of roughness (almost undetectable to someone who does not fly my plane regularly).

-I have noticed that if I lean the engine out partially or if I richen it up with a couple of turns from the point of roughness, my not only do I burn 10gph but the CHT's will also remain close to 400 on #2, #3, and #4. From my limited experience, our engine appears to like running slightly LOP as far as CHT's are concerned.

-My recommendation to you is to invest in an EDM 830 and keep all your factory gauges to meet legal needs. Mine cost a grand total of $2700ish including the installation by ly independent IA. Shoot me a message if you want more info.

 

 

[carusoam]

Deakin is good.

But, he isn't writing about specifically about Mooney M20Cs, their care and feeding...

Take what you learned from Mr. Deakin, and blend it with what you can find written in MS.

Finding information about running the O360 LOP... Hard to do.  But, there is some guidance.

Finding how to get a low cost engine monitor...  MS has a guy that specializes in used monitors.  So many used monitors have become available as others a upgrading often.

OAT is good to have.  Yours may be in the windshield.  You are sure to know what the temperature is when ice is forming on it.

Also look up the carb temp indicator.  Good to have.

There is plenty to know about the Marvell Schebler carburetor and how the two fuel jets are controlled.

Last question.  Do you have a fuel flow gauge?  It is a nice piece of information to have to help from running out of gas.

These are all things that didn't exist when your plane was built.  But, they have been around so long they are low cost compared to the value that they have.

Avoid running out of gas.

Avoid running into thunderstorms.

Avoid flying VFR into IMC.

Avoid getting ice on the plane.

Know the weight and balance and the Density Altitude.

Some of the basic tenets of flying old Mooneys.  Mostly stuff I have learned or relearned here.

PP advice, not a mechanic or CFI.

Best regards,

-a-

[Cyril Gibb]

On May 27, 2016 at 8:38 PM, MarinMooney said:

I need help!

I am trying to be a conscientious as I can when running the O-360 on my 1963 M20C.  I have been on forums, and read as many articles as I can find.  The series of articles by John Deakin was very informative and technical.

Based on the graphs in John's articles, he advocates adhering to a CHT limit of 400F.  But he contends that each of the cylinders will read differently, so since I only have one gauge, it is very inaccurate.

Additionally, he discusses leaning procedures, and contends that 50 LOP is about the worst place to run an engine.  50 LOP is exactly where some of the documentation I have read says to run the engine.

John's articles are from 1999, and I assume there is some new thinking on how to run the O-360 from an economical standpoint, a power standpoint, and a wear and tear standpoint.

I know I have spanned quite a few topics, but does anyone have either a concise explanation of the current logic on MP, RPM and leaning procedures?  Alternatively, if there is a document that spells out the procedures, I would love to read it.

I am wondering if I am out of luck having just one CHT and EGT gauge.  Maybe it is time to invest in individual cylinder gauges!

Thanks,

Steve

Not sure if it was your typo or not, but Deaken is emphatic that it's 50 ROP that's worst for running your engine, not 50 LOP.  The advantages of LOP have been understood since the 1930s.  It's unfortunate the old wives tales of LOP being bad rise like the Phoenix every few years.

[Cruiser]

If you look at any internal combustion engine performance graph you will see that the BSFC occurs slightly lean of peak EGT.

BSFC is a measure of the fuel efficiency of any prime mover that burns fuel and produces rotational, or shaft, power. It is typically used for comparing the efficiency of internal combustion engines with a shaft output.(wikipedia) 

There are several other benefits and subtleties but basically LOP operations takes advantage of this fundamental fact. 

[Cruiser]

On 5/27/2016 at 8:38 PM, MarinMooney said:

I am wondering if I am out of luck having just one CHT and EGT gauge.  Maybe it is time to invest in individual cylinder gauges!

You are not "out of luck" but if your engine is not performing consistently between cylinders you have no way of knowing this. If you follow the rules of operation this is not necessarily a problem other than the fact that you are not getting the maximum benefit from the output of your engine. Fuel savings (i.e. $$$$$$) is the carrot used to "sell" the method. In real world operation it also results in operating parameters that are less demanding on your engine and therefore better for it's health and longevity. 

[Hank]

My C would not run LOP until recently, it would just vibrate and shake. Now I can sometimes get almost 25°LOP, all it took was overhauling the carb, rebuilding the doghouse and the carb heat box. But boy, does it slow down when I go there. I generally ripen 50°ROP, and average right at 9gph block time. Flying high (800-10,000 msl), I've been known to fly right at peak. Performance is often very good. Wish I had fuel flow . . .

another benefit to all of this work is that I have picked up 10-12 mph, and had to relearn all of my power settings as I was suddenly too fast. Now I indicate in the mid to high 140s mph at 9000-10,000 msl, and have seen 165 mph at 1000 msl.

Yesterday going to lunch, I climbed out WOT/2700 and my CHT was right at the edge of the green stripe in my single factory gage. Once I leveled off at 6500 and pulled back to 22"/2400, temps fell nicely. But the factory gage is very imprecise and has very few numbers in it. Groundspeed was variable weaving between cloud tops but was mostly in the 135-140 knot range.

[Mooneymite]

If you are not using Tempest fine wire plugs in your O-360, I  would suggest you consider them at (or even before) your next plug change.  They made a huge difference in how lean my engine would run smoothly.  While I don't  have a gee whiz engine analyzer, I do have an accurate fuel flow gauge.

 

[DXB]

The POH definition of LOP in my carb'd plane seems a little sketchy.  Cruising at 7-10k, I get roughness at around 25 LOP on the leanest cylinder per the JPI, but the others are typically still ROP at this point.  Is this truly running LOP? Certainly not in the way one can run LOP with balanced injectors.

Importantly, my leanest cylinder varies from flight to flight - either #2 or #3 -  and I suspect it can change during a flight too. Prior to installing the JPI, this explains why my old single EGT probe on #2 didn't consistently predict when the roughness would occur.  

To help the mixture distribution, I've started pulling throttle back just slightly from wide open and also using partial carb heat if needed to raise carb temp to at least the high 40s F.  This hasn't made an obvious difference in how far I can lean though.

For folks like Hank, I wonder if  apparent changes in ability to run LOP after work on the intake, carb, and doghouse really just reflect changing the mixture distribution and thus the leanest cylinder. Without FF, it's hard to know if you're really running leaner or not.