How ROP am I

[bonal]

I will give this a shot. Our 64 D/C has no engine monitor just the standard gauges for that year model. So based on that I'm trying to figure out how ROP I run. My normal procedure after level is to let airspeed build then reduce rpm to 2400 to 2500 depending on OAT and altitude. Then set MP to desired again depending on OAT and altitude looking to keep CHT as cool as possible usually I can get as low as 360ish and oil temp to come down to around 200 to 205. Once MP is set and things start cooling down I begin to set mixture watching my EGT which of course has no indication but POH indicates 25 degrees for each hatch mark on the gauge. I usually see the needle reach the middle of the range sometimes one or even one point five passed half way before I detect the engine starting to miss. This varies depending on air conditions but I have never seen the EGT drop passed peak as I lean. If I'm at 6500 or above altitude I do the throttle out just enough to see MP move ever so slightly and set RPM to give me Rpm/1000 plus MP equals 47 which based on all I have read is a safe power level.

So, can anyone tell me based on better monitoring equipment how rich of peak I run. I'm going to try adding a little carb heat as others have noted an improvement in fuel/air distribution to all cylinders and see if I can find peak EGT. I understand all our old o360's are going to perform differently but just curious what the collective wisdom of MS might opine on the subject.

thank you in advance for your thoughts.

[Guitarmaster]

Leaning until rough and then enriching until smooth, usually results in a close to peak egt setting. At least it did in my IO360 equipped Mooney. In my carbureted 310, it never gets rough, it simply quits. THAT happens around 40 LOP.
To be brutally honest, you really have no idea what your engine is doing without an engine monitor. If you have no plans to install one, just listen to your motor. It will tell you when it's happy and it will also tell you when it's angry.
Your single-point CHT and EGT are only giving you 1/4 of the story. But at least it's part of the story. Yes, if I remember correctly, those marks are 25 degree marks.
There's really nothing you can do to hurt these engines when you're below 65% power.
I changed the way I operate my engines after going to the lycoming seminar at Oshkosh. 65% and below: peak, above 65%: 100 ROP. This came from a Bonanza owner with 2200 hours on a 520 and never been topped. Either he had the unicorn 520 or he was doing something right.... or both.


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[Jim Peace]

I don't use MP for leaning, using the JPI 900 in a 64c I find that it will show the word LEANEST when it is just beyond running rough.  Before I had the JPI I think I used to see peak temp before it sounded like all hell was breaking loose...with the JPI it gets a bit uncomfortable before it shows the word LEANEST then I make it 100 degrees richer from what it stored peak temp as..

I seem to get book numbers for FF....

I know this probably does not answer your question,,,hopefully convince you to get a good monitor...

get a good monitor and a CO detector...everything else is just fluff......

[Hector]

Your single factory EGT is likely on your #3 cylinder exhaust (unless someone has moved it), however, given that your engine starts to run very rough before reaching peak on #3 I would say one of your other cylinders is peaking way before #3. In your case I would pay attention where the EGT gage is when the engine starts to run rough then enrich to 100 ROP from that point if above 65% power. You will probably still be a bit less than 100 ROP on the leanest cylinder but probably fine if temps are cool. In my C it is not always #3 that peaks first. In fact, I see #4 peak first quite often depending on circumstances. I do have a JPI730 installed.

BTW, I think the magic number for C’s is 46 not 47.

 

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[Cruiser]

You might try going higher altitude and low RPM setup for a very low power, say 55% then try leaning to get the EGT to drop (show peak). If it works you can reference the peak position on the EGT gauge for a comparison. 

Then try the same configuration at lower altitude.

If you can't find PEAK there is no way to know how much LOP/ROP you are on that cylinder.

Maybe someone here can indicate which cylinder is the richest and which is the leanest for your engine model. They normally are all very nearly the same

[PT20J]

In my experience with Lycoming 320/360 series engines, leaning to roughness and the richening to smooth yields 25-40  deg LOP in fuel injected engines and near peak in carbureted engines (except for the PA28-161 which will run smoothly LOP).

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[Shadrach]

13 minutes ago, PT20J said:

In my experience with Lycoming 320/360 series engines, leaning to roughness and the richening to smooth yields 25-40  deg LOP in fuel injected engines and near peak in carbureted engines (except for the PA28-161 which will run smoothly LOP).

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My experience is that it varies with MP available. 1500msl my IOA1A will run smooth to 100LOP. At 12,500 I start to feel the power variance from cylinder to cylinder around 15-20LOP.

[PT20J]

13 minutes ago, Shadrach said:

My experience is that it varies with MP available. 1500msl my IOA1A will run smooth to 100LOP. At 12,500 I start to feel the power variance from cylinder to cylinder around 15-20LOP.

Good point, Ross. I was thinking of cruising around 5000 - 8000 ft.

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[Shadrach]

Just now, PT20J said:

Good point, Ross. I was thinking of cruising around 5000 - 8000 ft.

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In that range mine probably runs smooth up to the lean side of the numbers you’ve posted. My engine runs cool enough that I rarely lean beyond 40 LOP usually much less. I’ve come full circle now and find that leaning to peak or just beyond on my richest cylinder is my GoTo setting in cruise.

[MIm20c]

From the reading I’ve done the o360 can take a lot of abuse. If you use the magic 47 number it will show slightly over 75% in the POH. At that power setting you’ll probably want 75-100 degrees ROP but some just run it slightly ROR and the engines are tolerant. I’ve found the carb cylinder distribution changes as the mixture leans. There is no clear peaking order like you have on an injected engine. The first to peak will not continue leaning in a linear way. Often as another cylinder peaks the first one might inch towards peak again. 

Personally I use a lower magic number setting and run my engine at peak.  

For the JPI users if the unit is in ROP mode it is keeping track of the first cylinder to peak. If it’s in the LOP mode it is tracking the last cylinder to peak. So if you’re in the LOP mode and go to leanest +100 to the rich side you might have the first to peak cylinder running close to peak egt.