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  #11  
Old 01-28-2020, 08:03 AM
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Low Pass Low Pass is offline
 
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Originally Posted by Dave12 View Post
Read any articles you can find written by Walt Atkinson, George Braly or John Deakins . These guys are the gurus of lop operations. They have done years of research on the subject. There are many good articles on AvWeb. I lean as soon as the engine is running, enriched a little for the run-up, full rich for takeoff. When I go to 25/25 for climb, I’ll start leaning. You have to have the means of closely monitoring each cylinder and a well balanced injection system to get full benefits from lop operations. When I level out at altitude, I’ll do the big pull back to 20-30 lop. The bottom line, watch those cht’s. They will tell the story. I’m running dual pmags and Precision Silverhawk Injection and this combination is very efficient for lop operations. It saves a lot of $.
Same equipment, same procedures, very closely balanced injectors, same results. Watch the temps and lean away.
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  #12  
Old 01-28-2020, 08:04 AM
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FWIW, the FF x 14.9 = HP rule of thumb only works when LOP, as that?s the only time you know that all (well, most) of the fuel is being turned into work. Once you?re in the ROP area, unburnt fuel is going out the exhaust and the rule no longer applies.
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  #13  
Old 01-28-2020, 08:21 AM
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Originally Posted by svyolo View Post
Mike Busch also has a bunch of very long youtube videos. Several involve LOP. His claim, that makes sense to me, is that when LOP you can calculate hp by just multiplying the FF by a fixed multiplier. The multiplier changes a little because of compression ratio, which makes sense to me.

For "normal" NA Lycoming (8.5-1) he uses 14.9 X FF (in lbs per hour) equals hp. If running lower or higher compression pistons it would change the same percentage as the C.R., at least theoretically.

There is a very simple formula that calculates HP for an engine, and it varies linearly with C.R.
I believe the rule of thumb uses gal/hr, not lbs/hr (unless my IO-360 is producing 500+ hp in cruise )

Mark
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  #14  
Old 06-29-2020, 11:21 AM
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sglynn sglynn is offline
 
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Default lean of peak

Thanks for this thread on running LOP. So is running 25F LOP a good spot?

My RV-7A has IO360-M1B with regular mags, no tuned nozzles. Just stock Lycoming from Van's catalog and I'm flying behind Dynon's HDX. I tried the big pull recently and was pleased to see Dynon HDX tells me when you move from ROP to LOP. Its pretty cool. Plus the engine doesn't stumble. I thought it would if I pulled mixture too far past peak. But engine seems fine. Fuel Flow decreases a lot - a good thing. Percent power drops.

So for en-route cruise is it okay to do "big pull" to LOP and then screw the mixture while watching EGTs to get them 25F LOP? And should this be the baseline setting for en-route cruise especially at altitude when endurance is important? Should I write it into the POH?

thanks
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  #15  
Old 06-29-2020, 11:52 AM
sailvi767 sailvi767 is online now
 
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If you are going to do a rapid pull to LOP leave the HDX in the normal mode. Do the pull and then select lean mode on the HDX. Slowly richen the mixture until you reach peak on the HDX then lean back to 25 LOP. If you do the big pull in lean mode you won’t get a accurate peak value.
George
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  #16  
Old 06-29-2020, 01:32 PM
Dave12 Dave12 is offline
 
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Quote:
Originally Posted by sglynn View Post
Thanks for this thread on running LOP. So is running 25F LOP a good spot?

My RV-7A has IO360-M1B with regular mags, no tuned nozzles. Just stock Lycoming from Van's catalog and I'm flying behind Dynon's HDX. I tried the big pull recently and was pleased to see Dynon HDX tells me when you move from ROP to LOP. Its pretty cool. Plus the engine doesn't stumble. I thought it would if I pulled mixture too far past peak. But engine seems fine. Fuel Flow decreases a lot - a good thing. Percent power drops.

So for en-route cruise is it okay to do "big pull" to LOP and then screw the mixture while watching EGTs to get them 25F LOP? And should this be the baseline setting for en-route cruise especially at altitude when endurance is important? Should I write it into the POH?

thanks
How is your fuel flow spread aka GAMI spread?
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  #17  
Old 06-29-2020, 09:35 PM
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RV10inOz RV10inOz is offline
 
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You can run LOP happily well above 75% power....no problem.

80% and above 60-80dF LOP
75% about 40dF LOP
70% about 25dF LOP
65% or less 10-15dF LOP

IMPORTANT NOTE: Do not use Lean Find functions as a normal operational tool. Great educational tool, but they all wind you up further LOP than you think.
Work out your richest cylinder and use it as your reference.

Next trap most people fall into. If you are 80% power when ROP, and you lean to an appropriate LOP power, that should be a 10% BMEP drop, like the big old radial days. That means you will end up at 72% power, which serendipitously is going to be around 25-30dF LOP.

If you are at 72% power and ROP, you will end up 65% power when LOP, and that will be around 10-15dF LOP.

The simple answer is read all John Deakins articles carefully, they are sticked somewhere here on VAF.
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  #18  
Old 06-30-2020, 10:41 AM
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sglynn sglynn is offline
 
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Default LOP with Dynon

David and others
Thanks for this data on running LOP with Dynon HDX. I'll go fly, try and post any significant tidbits. thanks
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