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  #31  
Old 08-04-2011, 11:37 AM
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rv6ejguy rv6ejguy is offline
 
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Originally Posted by allbee View Post
I want to throw a wrench into the equation here. Lets look at an automobile. In the old days we use to set the engine up with carbs for best idle. That's turning in the mixture(carb) until it stumbled, than back out until the highest rpm. That's what we did. Than came the emissions standards, they set the carb at the factory and put those covers over that gave a little adjustment but not much, than they eventually sealed the mixtures, which I would just drill out and do over anyway. But the factory setting was always in about 1/4 turn from the highest rpm. Which in my book is a lean of peak senerio. Than altimately came fuel injection, which is set by the computer for 12:1 burn. We only have computers to maintain 12:1 fuel burn, there is no other reason for the technology. So If an automobile 4stroke engine can run LOP or 12:1 air fuel ratio, than why can't our 4stroke aircraft engines do it.

Oh and if you do LOP your doing the green thing, better on emissions. Your not stinking up the air and creating harmfull gasses. So not only are you saving money in your pocket, your helping out the air we breath.
Actually modern car ECUs are set to run AFRs at 14.7 (stoich and peak EGT) or even leaner (up to 17 to 1) with targeted AFRs using wideband sensor feedback during light load cruising. The new cats are capable of cleaning things up even well LOP. Engines will run in the high 11s or low 12s at full load and high rpm for max power and to preserve piston integrity but this is usually only for short durations in automotive use where 95% of the time the engine is at light load and running very lean for mileage and emissions.
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  #32  
Old 08-04-2011, 11:59 AM
RV8R999 RV8R999 is offline
 
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Until the sample size of engines run exclusively LOP to TBO (whatever that number ends up being) becomes sufficiently large it is all just smoke and mirrors....
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  #33  
Old 08-04-2011, 12:37 PM
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Toobuilder Toobuilder is offline
 
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Until the sample size of engines run exclusively LOP to TBO (whatever that number ends up being) becomes sufficiently large it is all just smoke and mirrors....
...The physics of LOP are not new - running big MP/low RPM and LOP was promoted heavily by Lindbergh back in the P-38 days as a way to stretch range. The thing that?s new is the ability to really get in and monitor the engine effectively. Back when it was rare to have an engine with even a single EGT probe, it?s no surprise that navigating the danger zone of detonation was risky ? you?re blind. Relate this to the navigation aids we have today ? after flying with GPS and on board XM weather, would anyone ever really try fly an approach to minimums with only an ADF?

The fact that Lycoming itself recommends peak EGT - the most potentially damaging condition short of detonation ? for economy cruise provides all the endorsement I need to run LOP. LOP simply ?takes it down a notch? (temp and pressure).

I think comprehensive engine monitors are a game changer, just like GPS and XM weather... It will just take a while to embrace the tools we have available.
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  #34  
Old 08-04-2011, 04:22 PM
jrovey jrovey is offline
 
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Originally Posted by Phlyan Pan View Post
I find it interesting that the line for specific fuel consumption is flat through the best economy range, the top of which is at peak. That suggests to me that jrovey's point is pretty correct in saying that his specific fuel consumption is best at peak. I'm assuming your speed at that point is slightly better than where you would be at lean of peak as well. So to me, that says that running at peak is the fastest economy speed you can go.
My Superior BSFC chart is not flat and it is lowest at peak EGT. I would post the graph but don't have permission yet. I agree the specific fuel consumption does not increase much and fuel savings is small when running a little on the LOP side but I like peak. Fastest way to get there for the least amount of fuel at a given power setting. I also agree with the cooling concern comments but my baffling works well and CHT's are in the 320 to 350 range.

My typical long distance flight starts with takeoff and climbout at 100 ROP and constantly pull on the mixture to keep it at 100 ROP. Once I get below about 70% I pull mixture back to peak. The entire flight except for decent is with the throttle all the way in. Assuming wind is not against me I climb to the percent power I want to cruise at which is usually about 65% and somewhere around 11-12,000 feet.
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  #35  
Old 08-04-2011, 05:01 PM
RV8R999 RV8R999 is offline
 
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I just don't believe it is as simple as lower pressure and temp when LOP.

Based upon the chart for the 0-360, running LOP results in lower power. If you run LOP and accept lower power (slower A/S) to save fuel that is great but why not run ROP and throttle back to the same power you had at LOP which also lowers pressure, temps.

The throttle is the most efficient fuel control we have.

The real test is to fly two runs at the same DA both at WOT (altitude sufficient to fly LOP at WOT of course)

Run 1: lean to whatever LOP setting you think is good noting FF, A/S, CHT, EGT, etc.. while maintaining alt

Run 2: lean to 100 deg ROP, then throttle back to the FF noted during the LOP test and note the A/S, CHTs, EGT and see how they compare.

Honestly I have not done this test and I'm very curious so I'll fly it tomorrow and tell you what happens.
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  #36  
Old 08-04-2011, 05:02 PM
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Ironflight Ironflight is offline
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I get just a little worried when I read of folks being happy LOP because of the "precision" of our available instrumentation these days. Oh, I'm not really worried (I don't think anyone is going to get in trouble....maybe "amused" is a better word. I say this because I can lean using time/temp EGT graphs, fuel flow, bar graphs, "Lean Prompt" functions....or leaning until things get rough, then smoothing it out - and I always end up in the same place.

it's just not as much as a rocket science as some might lead you to believe. The four-cylinder Lycs are just not the same as the turbo-charged big engines in the Bonanzas and 210's (the real target audience for Deakin and GAMA). I DO agree with Deakin on most all points, but I am just not that worried about the O-360's we fly normally aspirated. Peak, LOP, ROP - if it is smooth, it runs pretty well.

I personally run as lean as I can, and that is a good 1.0 gph below the "best power" line on Lycoming's "%HP vs. Fuel Flow" graph most of the time. That is generally LOP, and CHT's are always nice and coo. the absolute value of EGT doesn't mean a thing (depends on where you put your probes), so i don't worry about them. 1350 hours on the Valkyrie's engine running this way so far, with no issues.

Now one thing that I do pay attention to is that if you are deep LOP, you are going t go slower - by a measurable amount. But having the current mpg displayed on the EFIS has shown me that once you get close to peak on the Rich side, the mpg really doesn't change much you just get there slower if you go leaner.

Fly the way that you are comfortable, for sure! I like having an 800 mile range, so I lean it until it squawks, then smooth it out a little. The graphs are happy, as the engine appears to be. I haven't seen much evidence that running this way hurts the powerplant - so long as I don't lean above 75% HP (as recomended by Lyc), and am reasonable between 65-75%. Below that, you can't hurt a thing!
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  #37  
Old 08-04-2011, 05:33 PM
Sig600 Sig600 is offline
 
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Originally Posted by RV8R999 View Post
Until the sample size of engines run exclusively LOP to TBO (whatever that number ends up being) becomes sufficiently large it is all just smoke and mirrors....
Shack.......
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  #38  
Old 08-04-2011, 08:53 PM
DENMACRES DENMACRES is offline
 
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Smile LOP -50-60*

IO-360, HI COMP. AFP BALANCED INJECTION, JAMES COWL-PLENUM, IN A -6 IT's FAST AND COOL. 298-306 CHTS AT 8000' CRUISE, OVER 700hrs. A LOT OF THIS AT 75%. YES I GET MORE POWER ROP, JUST CAN NOT PAY THE FUEL BILL.
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  #39  
Old 08-04-2011, 11:33 PM
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allbee
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I also don't believe in peak operation for that is the hottest temps on the EGT which can kill your exhaust valves. Now if you let things go without monitoring than yes you can have an egt go high on lop and that would be desasterous.
While reading about your method of operation I was pleased you are doing many things right for the right reasons, but this statement above has me worried. It is plain wrong to say the higher EGT will kill your exhaust valves. That is simply not true, do the research and you will see why.

If you are motoring along all nice fat and happy, LOP and you see on your dynon EMS with its EGT display start flashing a rising and falling EGT, what would that mean to you? A disaster? Lets ask the question with more details to help, the EGT starts rising and stays up, maybe the odd retraction but its fluctuating above 1500F, and likely the CHT is dropping a bit. What does that tell you?

Also, fly along at 20-40 LOP and turn one mag/ignition off for 10-20 seconds, what happens? EGT's all go over 1500 +, speed drops off a bit and CHT's do what?

You are operating your engine nicely but it seems not fully understanding why you are doing a good job. And maybe not appreciating the fault finding value of all the science and information you have at your finger tips.

RV8R99
Quote:
I just don't believe it is as simple as lower pressure and temp when LOP.

Based upon the chart for the 0-360, running LOP results in lower power. If you run LOP and accept lower power (slower A/S) to save fuel that is great but why not run ROP and throttle back to the same power you had at LOP which also lowers pressure, temps.

The throttle is the most efficient fuel control we have.

The real test is to fly two runs at the same DA both at WOT (altitude sufficient to fly LOP at WOT of course)

Run 1: lean to whatever LOP setting you think is good noting FF, A/S, CHT, EGT, etc.. while maintaining alt

Run 2: lean to 100 deg ROP, then throttle back to the FF noted during the LOP test and note the A/S, CHTs, EGT and see how they compare.

Honestly I have not done this test and I'm very curious so I'll fly it tomorrow and tell you what happens.
You should do the test, and then you will see exactly what we are all on about. At the same %HP and in the safe detonation margin area, you will get the same speed however your Fuel Flow will be greatly more ROP. I do not recall the numbers now, but for me it was around 35-40% more fuel. Look at the charts you can work it out for yourself.


As for the LOP guys getting better life out of there engines, mate the data is in, it was in back in the 50's and 60's. ANd its back again now. The data and knowledge is here now, just some folk take a long time believing something different to what they were taught and practised for so long.

Here is a little story......., What colour is a Swan? Ask your child to draw a picture of a swan. I bet it is White in colour. Go back a couple of hundred years.....ask the question and all the scientists of the time would swear on a stack of bibles ALL Swans are white. end of argument. Well the British or the Dutch (cant recall who it was) sailed into Western Australia and they saw all these Swans, and they were jet Black. So if you ask me what colour is a Swan, I say it depends. But ask most people 200 years ago they would continue to swear balck and blue they are all white. And take some convincing too!

Have I ever mentioned attending an APS seminar......

And Paul Dye's comments for lower HP Lycomings operated as he suggests. Simple as that but it pays to understand exactly why. It also pays to know what your monitor is telling you. It will save you money longer term and may save your life.

DB
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  #40  
Old 08-05-2011, 06:11 AM
sailvi767 sailvi767 is offline
 
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Originally Posted by DENMACRES View Post
IO-360, HI COMP. AFP BALANCED INJECTION, JAMES COWL-PLENUM, IN A -6 IT's FAST AND COOL. 298-306 CHTS AT 8000' CRUISE, OVER 700hrs. A LOT OF THIS AT 75%. YES I GET MORE POWER ROP, JUST CAN NOT PAY THE FUEL BILL.
What compression are your pistons?

George
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