JonJay

JonJay

Well Known Member
I know this subject has been beat to death, but in all the discussions and wonderful reference to articles discussing LOP/ROP and techniques (not to be argued here please), I would like to know your basic leaning procedure.
How long into cruise do you wait before you lean? Immediatley? at any altitude?
My engine monitor (EDM930) has a lean find feature that I think I have figured out. However, I see a lot of folks refering to running 100deg LOP or some such figure. On what cylinder? My richest will be at peak, my leanest might be at -60deg LOP. Is that running at -60deg LOP?
If I pre-lean (IO-360) by leaning to slight loss of power, then enrichen slightly, things seem to be right at the above figures, leaving me no room to lean more agressively, like to -100 LOP. I understand this might be typical unless you put it Gammi Injectors?
When I cross check my fuel flow with Lyco. manual, they are exactly inline with the charts. So why not lean to fuel flow at a given power setting and let the EGT's fall in line, which they seem to do.
I think I am suffering from too much technology. If I fall back to my old training days, lean to roughness, enrich slightly, fly on, things seem to be set.
Thoughts?
 
First of all, balance your injectors. Give Don Rivera at Airflow Performance a call and he'll help you out. You don't have to blow big buck$ on gami$. Work with AFP to get your "gami spread" (delta in fuel flow between EGT peaks across all cyls) down as low as you can. Then you won't have to worry (as much) about one cyl being ROP and the other being LOP.

100 LOP is unnecessary imho. You don't need to go so lean. Read up on Deakin's "Pelican's Perch" columns on Avweb and you'll see that you don't have to go so far LOP to reach the sweet spot. http://www.avweb.com/news/pelican/182583-1.html

Anyway, get your gami spread tightened up (and again, I'm talking fuel flow delta here, not EGT delta), and then you can really take control of your economy.
 
Recall Message

Upon further reading of several articles, posts, etc... I have determined that this subject has far to many variables to answer simply. I will continue to educate myself. Thanks.
 
You are right about all the instructions and options. I've tried to simplify it. My GRT calculates percent power. When ever I am at 75% or above, I keep the mixture at least at 100 dF rich of peak to avoid detontation.

As long as I am under 75% power, I am free to lean to anywhere I want. I run at peak or just LOP, wherever my engine will run smooth. I have tuned AFP injectors so all my cylinders peak at the same fuel flow. However in the Rockets, we get some backflow from the flow divider at low fuel flows so sometimes I can run 50 dF LOP and other times, it stumbles.
 
It should be that simple, and I think it is. Per Dan's suggestion, I was able to get ahold of Don at AFP and have a simple procedure to get my spread on each cylinder, so I am hopeful that I will be able to get my cylinders matched up soon. According to my JPI, if I am using it correctly, my current spread is 1.0. I dont stand a chance at operating LOP effectively with that kind of spread.

Thanks.
 
Nope, you sure won't although that really isn't too bad, but it can be much better. You want to avoid situations where some cylinders are LOP but others are running in the detonation zone.
 
n714b said:
For another perspective, check out what the guys at Advanced Pilot Seminars have to say about running LOP or ROP. John or Walter are experts on the subject.

http://www.advancedpilot.com/
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They certainly are. Although the science and logic I am sure remains the same for our smaller bore engines, they seem to relate all of their stuff to big bore sixes and "cruising to destination" at thousands and thousands of feet in a Bonanza. Most of my flying is under 4000ft and sight seeing or just pounding about with no specific purpose but to have fun. I have learned a lot by reading the articles and agree that our traditional methods of operating these engines is far from ideal. I just need to take what I have learned and apply it to my missions and engine. Never had, or needed, mixture control in my Aeronca, and my Bucker has only one EGT/CHT. This is all new to me, along with my CS prop, and oh ya, flaps! Like the saying goes, I have a licence to learn.
 
One quick way

Which I discovered during my IFR training is to yank the red knob until the motor just quits or stumbles.

Then feed it forward until it just runs smooth...Ya I know this sounds like "lean to roughness" and it is except that I know my rougness is at about 100F LOP on the richest cylinder.

Saves a lot f faffing around trying to get it just right, but of course this is not the most efficient place to run the motor either as you want between 25 and 50F LOP for that...But its the method I've settled on.

Frank
 
f1rocket said:
As long as I am under 75% power, I am free to lean to anywhere I want.
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I've always found it interesting that some pilots are content to take the "cliff" approach with that magic 75% number. In other words, if you're running at 75% power, you're sorta conservative about leaning. But at 74% power, run the mixture anywhere. What happens at that magic 74.99999% cliff that makes it OK to lean more aggressively? DON'T ANSWER THAT. I'm just playing devil's advocate.

Another way to think about it is that the "red zone" or the "bad box" or whatever contemporary vocabulary may be...well, that caution zone shrinks as % power is reduced. So why rely on the hard edged "cliff" when you can take a slightly more linear approach?
 
Well, that's an interesting question and the obvious answer is "Nothing happens.". This is more a factor of where I run my engine at cruise. I think that with the 4-banger, you tend to run above 75% power more often in cruise than I do with the 6-banger. I tend to run under 75% power in cruise nearly exclusively since the additional power doesn't gain me significant speed versus the increased fuel flow.

My explanation was more black and white than the reality of how I apply it. At times when I am over 75% power, I do lean to 50dF LOP since I have that capability, so I employ my logic in a more linear fashion.

Another factor is altitude. I like it smooth so I tend to cruise at higher altitudes. Over about 6500 MSL, WOT gets me 75% power anyway. So my flying just happens to cause me to spend a majority of the time under 75% power. Besides, with the cost of fuel, I can't afford too many cruises at 17-24 GPH when I can go 10 kts slower and burn just 10 GPH.
 
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