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  #11  
Old 10-22-2018, 07:02 AM
togaflyer togaflyer is offline
 
Join Date: Apr 2013
Location: Cleveland Ga
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I have an IO 540 with 9:1 jugs. The plane is unpainted so that may account for the loss of a few knots. I have a Garmin G3X system and used the lean assist. My cylinders run 360 to 390 ROP. I showed -43 LOP on the last cylinder to peak, as my LOP setting. OAT was 10c at 9,500.


Question, how LOP do you go, -20, -30, -40 or ?. What power setting do you see. Are you looking for any particular numbers when setting to LOP. I was at 58 percent, is that about right or should it be set higher.

Last edited by togaflyer : 10-22-2018 at 07:12 AM.
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  #12  
Old 10-22-2018, 07:59 AM
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DanH DanH is offline
 
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Quote:
Originally Posted by togaflyer View Post
Altitude was 9,500, speed at 150 true, 9.9 GPH, 58 percent, manafold at 19.8 percent, prop at 2390, CHTs between 331 and 364, EGTs between 1325 to 1360, LOP was -43 to -64 degrees. Engine felt good.
Quote:
Originally Posted by togaflyer View Post
I have an IO 540 with 9:1 jugs. The plane is unpainted so that may account for the loss of a few knots. I have a Garmin G3X system and used the lean assist. My cylinders run 360 to 390 ROP. I showed -43 LOP on the last cylinder to peak, as my LOP setting. OAT was 10c at 9,500.

Question, how LOP do you go, -20, -30, -40 or ?. What power setting do you see. Are you looking for any particular numbers when setting to LOP. I was at 58 percent, is that about right or should it be set higher.
Let's tidy up a few fundamentals before moving forward.

Manifold pressure units are not a percentage. It is expressed in inches of mercury (abbreviated ""Hg"), typically measured at the intake port of the right rear cylinder.

You did not mention throttle position. We would generally assume you were at wide open throttle at this altitude. However, 19.8" Hg is a little low as compared to some other Vans examples. Could you confirm throttle setting?

Your exhaust gas temperatures do not matter in absolute terms, so knowing they were between 1325 and 1360 is useless information. Here the only EGT information of note is where you are relative to peak, and you've noted -43 to -64 degrees. As others have commented, there is nothing wrong with being that lean, but it puts you pretty far down on power, so airspeed will be reduced as compared to what most RV-10 owners post as normal LOP cruise.

Which brings us to your "How far to lean?" question. The answer is "As lean as you wish", the limits being (a) unacceptable loss of airspeed, or (b) engine roughness. What is practical? Lycoming has always suggested peak EGT as the economy cruise setting. Despite much rock throwing (at Lycoming), you'll note that LOP devotees very often suggest something like a whopping 10 degrees LOP at altitude. Neither is wrong.

At 9500 feet you should be at wide open throttle, and if so, the only way to increase indicated percent power (you reported 58%) would be to increase RPM. Again, there is no "wrong" RPM within the practical range one might select for cruise. More will require higher fuel flow, less will require less. You'll go faster or you'll go slower. Almost everyone has a favorite setting, usually based on comfort (like perceived vibration) or old belief (the way they always did it). Others enjoy mapping every possible combination, then developing an operating guide based on reams of data. That's cool too.
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Last edited by DanH : 10-22-2018 at 08:02 AM.
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  #13  
Old 10-22-2018, 08:12 AM
togaflyer togaflyer is offline
 
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Dan, I was not at WOT. I pulled back to 60 percent before doing a slow lean to peak. Once LOP I never push it the remaining throttle in I had left. I was a bit Leary of the red box syndrome. So I should be WOT. At 9.5 I was still up around 70 percent engine power, so should I do the big pull down to 10 gph, then enrich to see where peak is at. Sounds like I definitely gave up some speed by not being WOT and maybe too LOP.
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  #14  
Old 10-22-2018, 08:37 AM
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Carl Froehlich Carl Froehlich is offline
 
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It seems you never did a GAMI run to balance injectors. Do that before anything else. It only takes a few minutes and as you do it you will get experience with LOP operations.

On my IO-540 (new from Van’s) the initial GAMI spread was about 1 gph. LOP operation was horrible. It took just three iterations (and change out of four of the six injector nozzles) to get the GAMI spread down to 0.1 gph. Get your replacement injector nozzles from AirFlow Performance (I think $26 each). Don will help you figure out what size to get.

Typical LOP ops at 8K’ is WOT and 2400 RPM for 173kts TAS, 11.5gph. Above 12k’ it is WOT and 2450RPM to get the same 170+ speed but fuel burn is down to a little over 10gph. Drop the RPM and you will save gas at the cost of some airspeed. Have the plane at max weight and you will of course lose some airspeed.

Go out, burn some gas and get some engine data. No better way to spend a weekend.

Carl
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  #15  
Old 10-22-2018, 01:26 PM
rdrcrmatt rdrcrmatt is offline
 
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Location: Milwaukee, WI
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Quote:
Originally Posted by togaflyer View Post
Dan, I was not at WOT. I pulled back to 60 percent before doing a slow lean to peak. Once LOP I never push it the remaining throttle in I had left. I was a bit Leary of the red box syndrome. So I should be WOT. At 9.5 I was still up around 70 percent engine power, so should I do the big pull down to 10 gph, then enrich to see where peak is at. Sounds like I definitely gave up some speed by not being WOT and maybe too LOP.

Until you throughly understand LOP, what's happening, now A/F ratio works, etc, you should not make power changes (throttle or RPM) changes while operating LOP.

Establish your cruise power setting, let your engine cool from the climb while ROP for 1-2 minutes. Then, start leaning to peak and move to LOP. If you need to descent, go ROP. If you want to climb, go back to ROP. Then when established level, repeat the LOP process.

Making power changes wrong can cause major roughness, or possibly wandering your way towards running at peak EGT, possibly above what's considered acceptable for extended periods of time. I'm sure it's a minor concern, but when teaching pilots about LOP operations, I strongly recommend keeping it as simple as possible. LOP for cruise, ROP for everything else.
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Last edited by rdrcrmatt : 10-22-2018 at 01:29 PM.
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  #16  
Old 10-22-2018, 02:34 PM
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DanH DanH is offline
 
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Quote:
Originally Posted by rdrcrmatt View Post
Until you throughly understand LOP, what's happening, now A/F ratio works, etc, you should not make power changes (throttle or RPM) changes while operating LOP.
Yeah, do it wrong and the scary clown pops out of the oil door.



Quote:
If you need to descent, go ROP. If you want to climb, go back to ROP. Then when established level, repeat the LOP process.
Descend LOP for as long it runs smoothly. I mean all the way to pattern altitude if you wish. It will run smooth way LOP when the prop is unloaded. Just go rich before pushing the power back in.

Climb LOP if you wish. Most RV altitude adjustments in cruise merely require raising the nose, no power change. Assuming constant flow injection, it will get richer as you go up. You may need to lean a bit as you go along, just like climbing on the ROP side.

Quote:
Making power changes wrong can cause major roughness, or possibly wandering your way towards running at peak EGT, possibly above what's considered acceptable for extended periods of time.
There is no time limit on peak EGT, only a manufacturer-imposed percent power limit.

You want simple? If it runs well and temperatures are low, it's fine.
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  #17  
Old 10-22-2018, 02:40 PM
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rv6ejguy rv6ejguy is offline
 
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I agree with Dan. We have several users who fly LOP in the climb, descent and even while doing formation work- any time you want to keep CHTs down, save fuel and don't need max power.
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Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW since 2003- 424.4 hrs. on the Hobbs,
RV10 95% built- Sold 2016
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  #18  
Old 10-22-2018, 02:57 PM
rdrcrmatt rdrcrmatt is offline
 
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Quote:
Originally Posted by rv6ejguy View Post
I agree with Dan. We have several users who fly LOP in the climb, descent and even while doing formation work- any time you want to keep CHTs down, save fuel and don't need max power.

I've always wanted to try it in the climb, but the window to hit seems pretty narrow and always moving. Leaving it WOT and using fuel to control power means flying it like a diesel! If only we could actually get a good compression ignition engine.
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  #19  
Old 10-22-2018, 03:17 PM
Mark33 Mark33 is offline
 
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Quote:
Originally Posted by DanH View Post
...
There is no time limit on peak EGT, only a manufacturer-imposed percent power limit....
So is there a rule of thumb for that "percent power setting"? My -4 has an O-320 and F/P Catto three blade prop. I generally cruse at between 62-65% power and a little bit ROP burning about 8.2-8.5 GPH. At 9500' my MAP is indicating about 19.5". I would love to run LOP but my engine starts to spit and sputter if I try to go any leaner than peak. From what I've understood up until this point that running at peak wasn't heathy for the engine. At peak and at those flight parameters I can shave about another 1 GPH off of my fuel consumption. So once again, is there a rule of thumb that should be followed?

Thanks,
Mark
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  #20  
Old 10-22-2018, 03:41 PM
woxofswa woxofswa is offline
 
Join Date: Sep 2007
Location: Mesa Arizona
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I just yesterday finished a rather long Baja trip in my RV10 with BPE IO-540 9.1

I have played around with LOP quite a bit, but the resultant loss of airspeed just doesn’t make the rather slight increase in nm/gal seem worthwhile to me unless specifically needing to extend range. The engine runs smooth enough but I always feel like I’m sitting on eggshells.
The big dog likes to eat. Feed it and it purrs like a kitten. and the few gallons that those precious last 15 knots cost seem well worth the sheer pleasure of passing the other aircraft in the group (210’s, Beech’s, Mooney’s) and really energizes the air to air trash talk.
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Last edited by woxofswa : 10-22-2018 at 03:53 PM.
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