Manual Specifies O-360 LOP?!

[cctsurf]

I'm making up my own checklists for my 1962 M20C, and as I'm writing them up, I'm cross referencing them with the POH.  As I read through the manuals they specify running the Carbureted O-360 engine Lean of Peak, as far as I can tell!  I have always understood that this was a VERY questionable idea, pretty much asking for trouble.

I cross referenced this with the manual for a 1967 M20C, and the advice was the same.  Does anyone run 25 Deg LOP as the manual describes?

 

Here is the paragraph in question:  

Lean the mixture for smooth operation (reference Lycoming's Operators Manual.)  The Exhaust Gas Temperature Indicator is to be used only as an aid in setting the mixture during cruse at powers up to 75% power, but not  take-off, climb, or descent.  For lean-out procedures at 75% power or lower, lean to peak temperature, then lean until temperature drops 25 Deg F. minimum.

 

In the '67 manual, it continues talking about Best Power Setting:

To obtain a best power (maximum airspeed) setting, lean to peak temperature and then enrich mixture (push control forward) until the indicator shows a 100 Deg F. drop (four marks on the gauge) from the peak temperature.

 

This has probably been discussed before, but I couldn't find it in a search.

Thanks,

James

[Andy95W]

I thought it must be a typo, but yes, my manual says the same thing. Funny, though, the 1970 POH says to ENRICHEN 25 degrees after finding peak.

And it only took 8 years to find and fix the mistake in the POH!

[yvesg]

Mine says to Enrich 100 degrees, 4 lines... 1965

Yves

[bonal]

My POH says the same thing 75% lean to peak temp then past to 25 deg drop.  usually by then I'm running rough. it's very inconsistant and with only one probe you cant be certain what you have. for me its lean to rough then rich to smooth again. and keep an eye on the temps.  its amazing how much variation i will see on the EGT gauge depending on the conditions each day for the same power settings.

[orionflt]

62 C models are special aircraft, we can do more then the rest because they didn't know there was a limit.

Sent from my iPhone using Tapatalk

[Hank]

James,

Your 67 says the same thing as my 70 model, lean to peak then richen. Read your post again, that's what you wrote. Can't explain the 62 book, mine runs rough below peak regardless of what I do to smooth it out.

[carusoam]

If you can get the carb to run LOP, Document it!

1977 M20C POH states to lean below 75% hp. Using the lean til rough, then enrich til smooth...

Fuel flow through the carburetor has jets that are not the least bit balanced, compared to individual fuel injectors for each cylinder...

Bill Wheat, in a phone call, recommended the 77 POH because it was most up to date. Compared to my 65C's owners manual....

Best regards,

-a-

[Piloto]

I used to have a 66 M20C. I found that the best way to go is just to lean until engine roughness and then enrich slightly for smooth running.

 

José

[Hank]

If you can get the carb to run LOP, Document it!

1977 M20C POH states to lean below 75% hp. Using the lean til rough, then enrich til smooth...

Fuel flow through the carburetor has jets that are not the least bit balanced, compared to individual fuel injectors for each cylinder...

Bill Wheat, in a phone call, recommended the 77 POH because it was most up to date. Compared to my 65C's owners manual....

Best regards,

-a-

So where would our enquiring minds find an electronic 1977 M20-C Owners Manual? Or had it become a POH by then?

[cctsurf]

I hadn't refreshed, and was going to post the exact same thing that Hank posted above.

[bumper]

Well, not a Mooney, but I regularly operate my carbureted Husky A1-B, Lyc O-360 smoothly at 30 LOP in cruise - it typically won't get rough until about 50 LOP.

 

To get even temperatures on the analyzer and keep the engine smooth, I back off the throttle about .5 to 1 inch of MP so the throttle plate is (I'm assuming) adding turbulence to the induction air to help keep mixture distribution even. MT prop RPM is 1900 to 2000 and power is 50 to 55% 

 

At 6 - 7000 MSL, fuel burn is 5.8 - 6.0 gpm for 105 knots, not nearly fast compared to my Mooney, but the Husky can land there, or over there, or right there, in places I'd never take the Mooney (though Piper Painter might).

 

bumper

[Hank]

I back off on the throttle enough to make the MP needle move, but never ½" on the gauge. I'll try that next time. I've even played with the Carb Heat to no avail.

[carusoam]

My 65C came with these documents removed...I was happy that it had good Maintence Logs.

Calling MAC in Kerville, I got a treasure trove of data...

The 65’s owners manual was to keep the plane legal.

The POH from 77 was to supply the most full documentation that was available in 2000...

The 77 title page indicates it is a POH and AFM.

As for electronic version... I am not familiar.

When I sold the plane, the owners manual went with it.

Best regards,

-a-

[cctsurf]

carusoam, do you remember what this treasure trove of data cost you?  Just wondering,

Thanks,

[takair]

Flying with the Feds Monday so I was just checking for the right manuals. According to Mooney web site, correct one for my 64 is POH 1193. Somebody has it posted in the downloads section here on Mooneyspace. Sure enough it says to lean to 25 LOP......or that's how I interpret. That said, the AFM that I just downloaded from the Mooney site says to enrich 25. So much for consistency. You will also find the RPM limitations in conflict between the TCDS, the AD and the manuals.

[carusoam]

Documentation back in the day is nowhere like it is today. There are some errors in the documents that are misinterpretations or accidents by the typist.

I looked at the paperwork that was with my POH. It was the packing slip that covered both the owners manual and POH. But no record of the price could be found.

It couldn't have been too much. I bought the C and within a month I bought both manuals. My second child was four...months old.

Call the company, get the POH...then ask on MS about anything that doesn't sound quite right.

I tried to go LOP with my C, I was unable. Of course doing it with a single EGT probe wasn't helpful either.

I would support anyone that wants to try it. First understand how the fuel is distributed from carb to cylinders. Then how the air flow is balanced, or not...

There may be a setting that works...?

Flying LOP takes a touch more control of both air and fuel flows than the C and M have.

The IO550 is one of our best balanced engines...balanced airflow in curvy tubes. Balanced fuel injectors, one for every cylinder. All engines would benefit by this type of technology.

Best regards,

-a-