Lean of Peak

[N395V]

designs their cylinder bores with a taper

CHTs hover around 280-290F

My concern is the traper issue.

Long ago I remember removing the thermostat from my cars in the summer to improve cooling. Occasionally I (as many others) eventually never put the thermostat back in when winter came. Someone recently told me that the decreased winter CHTs reduced engine life significantly due to increased wear.

After 2 years of fighting high CHTs I added some ramps to the front of my baffles and was rewarded with better than expected results.

When running ROP my CHT spread is between 310 and 355 LOP it is 290 to 320. 290 to 320 concerns me as to low. I am comfortable at 320-360 but 290- 320 seems inordinately low.

Any comment or thoughts????????????????????????????????????

 

[fodrv7]

Lycoming Min CHT

Milt,
I have a straight valve from the same manufacturer as Dan and see similar figures as Dan, thought I can not go as high, as I have no Oxy. and the ANOs in Aus. limit flight to 10,000' without it. But there are no hills in Aus anyway.

More importantly, Page 3-15 of my Lycoming manual states: " For maximum service life of the engine maintain cylinder head temperature between 150? F (65?C) and 400?F (204?C)

Additionally Page 3-6 "....... CHTs should be maintained below 435?F (224?C) during high performance cruise and below 400?F (205?C) for economy cruise."

Be careful NOT to interpret these as limits. They are figures Lycoming recommend for longevity.

Good to see you looking after your aircraft's heart.

Pete.

 

[osxuser]

Looks like I've got my head in the sand as far as effiency of the RV's baffles and cowls are concerned. For my money, if My CHT's are that low, and never get about 360 or so in the climb, i'd start shrinking down my inlet size a bit to get an extra knot or two, but I'm nutty like that. Make it so the CHT's top out a 380 in a normal climb, and squeeze every last knot from that cowl by reducing frontal area.

 

[dan]

Looks like I've got my head in the sand as far as effiency of the RV's baffles and cowls are concerned. For my money, if My CHT's are that low, and never get about 360 or so in the climb, i'd start shrinking down my inlet size a bit to get an extra knot or two, but I'm nutty like that. Make it so the CHT's top out a 380 in a normal climb, and squeeze every last knot from that cowl by reducing frontal area.

I would if I always ran LOP. I run ROP in the climb, I run ROP when in formation as wingman. I do not want to create heat problems for ROP by accommodating only LOP.

 

[vlittle]

practice vs. theory

I've digested all of the theory and recommendations on leaning, but my real-world experience is different.

I have an Aerosport/Superior O-320 A1AC2, with ECI cerminil cylinders, conventional mags, roller lifters. Fixed pitch Sensenich.

I think the fundamental problem is that fixed-pitch props vary rpm & power as you lean, so it's difficult to use EGT/CHT as an independent measurement by fixing HP and varying mixture. I've taken to using rpm as the measurment of leanness (peak rpm being easier to determine than peak EGT)

When I lean, I see the rpm drop, but no increase in roughness. On the lean side of peak, the mixture control works as a throttle for me, with smooth running right to near cut-off.

This is probably attributed to Bart's engine assembly and the Superior sump giving me even fuel mixtures.

My CHT's on 1, 2, and 4 are all within 2 degrees (360-380F at cruise), and #3 is about 10 degrees cooler. About 1/2 of my oil cooler is blocked off, and the cabin heater bleed is off the rear baffle, down low near #3. I have a 1" riser on #1 to even things out. I've tried to increase #3 temps by blocking off the cabin air bleed by 40%, which has helped (counter-intuitive, but effective).

I saw one posting, and the Lycoming articles on leaning, but they all assume that over-leaning will give rough operation, and to richen from that point.

Should I just count my blessings or am I doing something wrong? Anyone with a FP experience the same thing?

One more thing... until I got the cylinder temps evened out, I could not use full power for more than a few minutes after takeoff from sea level. I'd see CHT on at least one cylinder spike over 435F. Even now, if I park the airplane for an hour then take-off again, I'll see higher than normal CHTs for take-off and have to reduce power and climb rate. %power on take-off is about 92%.

I suspect this is normal behaviour for the RV's.... is that true?

Vern

 

[Yukon]

Percent of power

Vern,

A very interesting insight here! I think this confirms Lycoming's contention
that LOP operation only facilitates lower percent of power operation and accomplishes little else. The constant-speed prop allows the engine to maintain cruise rpm, and therefore approx cruise thrust, and the aerodynamic cleanliness of the RV permits efficient reduced power cruise. The fixed-pitch prop immediately looses rpm when power is lost due to fuel starvation of LOP, the angle of attack increases to mailntain altitude and the airplane falls off step.

If I understand it correctly, Dan's engine, in it's tricked out configuration produceds around 210 HP. If he operates it at 33 percent power, by way of the LOP techniques, he is producing about 70 HP. This is about the same amout of power that an 0-320 makes at 55%, and close to the same fuel consumption and TAS. No free lunch in aviation.

John

RV-9 QB

 

[dan]

If I understand it correctly, Dan's engine, in it's tricked out configuration produceds around 210 HP. If he operates it at 33 percent power, by way of the LOP techniques, he is producing about 70 HP. This is about the same amout of power that an 0-320 makes at 55%, and close to the same fuel consumption and TAS. No free lunch in aviation.

Sure, if all you're looking at is power output and fuel burn, you are absolutely RIGHT!!!

However...what should not be overlooked about LOP:
- lower ICP (internal combustion pressure)...less wear & tear
- engine runs cleaner...considerably less in the way of carbon deposits
- engine runs cooler...less wear & tear
- much less CO (carbon monoxide) in the exhaust
- more miles per gallon per horsepower (higher efficiency at any HP output)

 

[Yukon]

Fuel = Horsepower

Dan,

I love physics! Now we are getting somewhere! Fuel=HP / HP=thrust / thrust = speed.

I wholeheartedly agree, less power equates to less wear and tear, less heat, less CO, less carbon, less vibration, fewer oil changes, fewer greenhouse gases, less noise, Democrats take over the Senate / return to the Whitehouse......................


John

RV-9 QB

Sure, if all you're looking at is power output and fuel burn, you are absolutely RIGHT!!!

However...what should not be overlooked about LOP:
- lower ICP (internal combustion pressure)...less wear & tear
- engine runs cleaner...considerably less in the way of carbon deposits
- engine runs cooler...less wear & tear
- much less CO (carbon monoxide) in the exhaust
- more miles per gallon per horsepower (higher efficiency at any HP output)

 

[vlittle]

LOP Sided

My AME (A&P in the USA) has always taught aggressive leaning (for O-320 150/160 HP):

1. lean on the ground for taxi (keeps the plugs from fouling)
2. aggressively lean at any power setting less than 75% as long as the engine runs smoothly.

When leaning on the ground, pull the mixture out enough so the engine will sputter when you apply take-off power. This prevents you from taking off with the mixture lean.

Now, at 8500', the mixture control is effective for me as a throttle (see previous post). Not true for every engine, but I'm lucky. As soon as I'm LOP, %HP drops, so I'm below 75% (55-65%) and in economy cruise. I can lean to ridiculously low power without roughness, but the engine RPM becomes sensitive to minor variations in airspeed or air temperature (air density).

At some point as the plugs and mags wear, I probably won't see this performance. I've prewired for e/pmags so at that point maybe I'll upgrade my ignition.

If anyone else sees this behaviour, please let me know. I want to know if it's due to the sump design, roller lifters, Bart's assembly or just luck.

Vern

 

[Yukon]

LOP with Fixed Pitch

Vern,

I'm no expert on this LOP stuff, but I'm sure we will hear from one soon......... I think what you are seeing is the normal effects of excess leaning on horsepower production. Due to the better flow characteristics of the Superior composite sump, your cylinders are leaning out evenly. As you pull the mixture past peak, your engine losses horsepower due to decreased fuel flow. Without a constant speed prop to mask the horsepower loss, you are unable to realize these phantom benefits of LOP that everyone talks about.

You don't mention any speeds or fuel flows? Could you do so for our benefit?

John

RV-9 QB

 

[vlittle]

Vern,

I'm no expert on this LOP stuff, but I'm sure we will hear from one soon......... I think what you are seeing is the normal effects of excess leaning on horsepower production. Due to the better flow characteristics of the Superior composite sump, your cylinders are leaning out evenly. As you pull the mixture past peak, your engine losses horsepower due to decreased fuel flow. Without a constant speed prop to mask the horsepower loss, you are unable to realize these phantom benefits of LOP that everyone talks about.

You don't mention any speeds or fuel flows? Could you do so for our benefit?

John

RV-9 QB

Hi John

I'll make some measurements and post them, but I expect that fuel flow will probably track horsepower for 'best economy' settings.

As I recall, I was seeing 6-7 gph with an *INDICATED* HP of 55% (on my Micromonitor). Since indicated HP uses RPM, MAP and fuel flow to compute HP, it may not be accurate when running LOP. I think the HP computation assumes best power mixture.

I need to record FF, DA, RPM and MAP and work out the actual percent HP when running LOP.

My gut feel is that FF will track 'best economy fuel flow' for the resultant HP within a reasonable range. Using the mixture control to control horsepower is a bit unconventional, but my engine seems ok with it.

Fixed pitch props are great, but they sure complicate engine managment!

I think there was a recent Kitplanes article that discussed %HP computations. As I recall, it provided updated Lycoming data (that is more current than their manuals) and simplified the computations using Density Altitude rather than Pressure Altitude in the charts. Since most EFIS systems will give a direct reading of DA, this makes in flight estimations easier than using the published Lycoming eye-charts.

Perhaps Kevin Horton can provide us with a formula that we can program into a calculator that will directly provide us with %HP from RPM, MAP, DA and perhaps fuel flow. It only needs to be accurate in the 50-80% range, I think.

Vern

 

[Yukon]

LOP Challenge!

Dan,

I think we can settle the efficiency aspects of this LOP thing, once and for all. Fill up your plane with 100LL and launch for Falcon Field on your next day off. Take that video camera of yours and train it on that engine monitor, filming it the entire flight. When you land here in Mesa, I'll pay to have your tank topped, as well as your return fuel, and we will review the tape over lunch! What do you say????

John

RV-9 QB

 

[dan]

I think we can settle the efficiency aspects of this LOP thing, once and for all. Fill up your plane with 100LL and launch for Falcon Field on your next day off. Take that video camera of yours and train it on that engine monitor, filming it the entire flight. When you land here in Mesa, I'll pay to have your tank topped, as well as your return fuel, and we will review the tape over lunch! What do you say????

The video camera would be a pain in the butt. How about instead we review the engine monitor data in Excel?

What exactly would you be looking for? All you're gonna see are straight lines for the duration of cruise, other than fuel quantity going down slowly.

 

[Yukon]

LOP Challenge

Don't you have a mount you use for filming aerobatics??? I would like to see what the engine/prop combination's reaction is to turbulence/up and downdrafts, and how long the airplane remains on step.

Excel would be ok to, I guess, if you can't work out the video.

John

 

[dan]

Don't you have a mount you use for filming aerobatics??? I would like to see what the engine/prop combination's reaction is to turbulence/up and downdrafts, and how long the airplane remains on step.

Not sure what any of this has to do with LOP...but anyway... The camera mount I have is crude & fixed...not designed to allow the camera to be aimed.

You won't see any change in any of the engine parameters in turbulence or convection. Why would you?

Not sure what you mean by on step, but that sounds like you want to know how the plane handles. How well it holds altitude or level wings or something. Sounds like a new thread to me.

 

[Yukon]

LOP Challenge

That's funny Dan......Shows our generation gap! 20 years ago, before we had LOP to argue about, guys would sit around and debate the "step controversy". That's the 5 kt or so advantage you get when the airplane is trimmed just perfect and flying at optimal angle of attack in cruise. Descending air will upset the balance, and before long you are slogging along at normal cruise speed, a little slower than step speed. Bottom line, step speed gain is real, just hard to maintain in turbulent air.

When your airplane encounters descending air, the autopilot will pitch the nose up and the prop governor will command a lower prop pitch. I want to see what the percent of power and fuel flow is under these conditions.

I find it hard to believe a man of your many talents can't find away to video his instrument panel! Tell me it ain't true!

John

 

[dan]

I'm familiar with the concept of the step. Just don't know what it has to do with LOP, or how engine parameters would be affected in the least. Ok, I'm done with this silly thread.

 

[BOBM]

My experience with the carb O320 F/P is that it runs very well LOP & the fixed pitch prop makes it easy to achieve LOP since it acts like a torque meter to give a direct reading of horsepower. Just set the RPM to the setting for a power level about 10% above that which you want to use for cruise at the existing density altitude, then lean the mixture to achieve the appropriate RPM. I normally cruise at no more than 65% in accordance with Lycoming recommendations, so set the power by the chart for 75%, then lean until I achieve the RPM for 65% ( usually a drop of about 100 RPM). It works the same way if you desire a lower cruise % of power. As stated in a previous post, I see a drop in airspeed of 5-8 kts (3-5%) & a drop in gph of about 20% vs running ROP. You know you have it right when you see the dramatic drop in cht & lower oil temp with this technique. The decreased fuel burn & resulting extended range of at least 15% is icing on the cake! This is a simple procedure that can be done precisely with a F/P prop, you don't even need an egt. With a constant speed, it would be a little more complicated since you don't have the RPM drop to show the amount of decrease in power. As someone stated in a previous post, leaning too much will result in an increase in SFC (higher fuel burn from less HP). You would have to go by egt (about 50 degree drop) & cht. I wonder if the engine monitors can see this, or do they just look at mp & RPM? Maybe someone who has a monitor that reads % of power could do a simple test. Just establish cruise at 75% with best power mixture, then, without changing anything but mixture, lean to 50 degrees LOP. Does the monitor show the reduction in HP or is it still reading 75%? Dan?

 

[Yukon]

LOP Challenge

Dan,
So what day are you coming over? Free gas is harder to find than a free lunch, silly thread or not! And I offering both to the first RV-7 that shows me 4.8 gph!

John

 

[vlittle]

LOP sided again

My experience with the carb O320 F/P is that it runs very well LOP & the fixed pitch prop makes it easy to achieve LOP since it acts like a torque meter to give a direct reading of horsepower. Just set the RPM to the setting for a power level about 10% above that which you want to use for cruise at the existing density altitude, then lean the mixture to achieve the appropriate RPM. I normally cruise at no more than 65% in accordance with Lycoming recommendations, so set the power by the chart for 75%, then lean until I achieve the RPM for 65% ( usually a drop of about 100 RPM). It works the same way if you desire a lower cruise % of power. As stated in a previous post, I see a drop in airspeed of 5-8 kts (3-5%) & a drop in gph of about 20% vs running ROP. You know you have it right when you see the dramatic drop in cht & lower oil temp with this technique. The decreased fuel burn & resulting extended range of at least 15% is icing on the cake! This is a simple procedure that can be done precisely with a F/P prop, you don't even need an egt. With a constant speed, it would be a little more complicated since you don't have the RPM drop to show the amount of decrease in power. As someone stated in a previous post, leaning too much will result in an increase in SFC (higher fuel burn from less HP). You would have to go by egt (about 50 degree drop) & cht. I wonder if the engine monitors can see this, or do they just look at mp & RPM? Maybe someone who has a monitor that reads % of power could do a simple test. Just establish cruise at 75% with best power mixture, then, without changing anything but mixture, lean to 50 degrees LOP. Does the monitor show the reduction in HP or is it still reading 75%? Dan?

Bob, you are a voice of clarity in the electron jungle. Set to 75% HP, lean to 65% or 100 RPM drop, check CHTs and look out the window for traffic.

The only caveat I would make: don't try to get to 75% starting with 85% because there is a danger of passing through the 'red zone' (detonation). Lycoming says one can lean anywhere below 75% HP.

I'll try it. Makes me happy to have a FP prop after all.

Vern

 

[N395V]

Here is a graph from one of John Deakins articles. Now whether you like him or not he presents some compelling actual data that suggests that LOP under controlled conditions may provide more benefit than harm and more opportunity than risk.

[/URL][/IMG]

I read the article relative to when LOP goes wrong and I think he is clearly correct. The Aussie Board was smoking dope when they published their findings.

Clearly the crew was not practicing LOP they were leaning the **** out of an engine not tuned nor instrumented for it. This may or may not have led to the disaster.

Now if you want to talk about smoke, mirrors and voodoo start a thread about flying "on the step". Airplanes should be flown in perfect trim if that is possible but from my generational learning, over 35 years ago, "the step" is that magical place where the plane enters the twilight zone and violates the laws of physics, that place where there is no drag or gravity only thrust and lift.

I have yet to see any scientific data that suggests that the step exists nor any data on how to get there.

Maybe next time I am at Falcon Field someone can show me a video of their aircraft instrument panel entering the step? We can watch the video over lunch(my treat) What will I see?
A magical 10Kt increase? Drastic reduction in BSFC?
Will flying "on the step" increase TBO?
Show me some data that the step even exists. The data above suggests that LOP works.

Why is it that most autos run LOP? Does GM want to shorten engine life or increase fuel consumption.
You really do not need a video of an engine monitor. The downloaded data tells you what you need to know about temps. Dans verbal reports of MP/RPM/TAS/GPH round out the info of importance unless of course you are suggesting that Dan and others who report their data are less than honest.

Dans experience matches mine and others and his numbers appear accurate to me.

You can argue over LOP all you want. I use it. It works for me. Far better than trying to find the "step"

 

[BOBM]

The only caveat I would make: don't try to get to 75% starting with 85% because there is a danger of passing through the 'red zone' (detonation). Lycoming says one can lean anywhere below 75% HP.


If you want 75%, do the procedure, then advance the throttle back to the 75% setting (assuming you have that much throttle left, depends on altitude). That way you never go peak or LOP above 75%. I have the low comp. 150 hp engine. I don't think it would be possible to detonate this engine on 100 oct at any power setting if temps are normal. That's probably true for the 160 hp as well, since it was designed for 91/96 fuel.

 

[osxuser]

I agree with being able to lean anywhere under 75% power won't damage the engine. When I'm flying the Cardinal I get it up to 10K feet in cruise, go to WOT prop sets my power, and I lean 'till it won't run smooth anymore (be that LOP or at peak, O-360A1A so it's usually right at peak) and it slogs right along. Pulled the engine for overhaul after 300Hr's of flying that way with no apparent damage. The crank, case, and all associated parts are still in fine shape. The cylinder were all 75/80 or higher when the engine was removed.

Yukon, it's silly to call anyone (even more so Dan, the king of documentation) out on something like this. I've personally flown with Dan (he gave me my "$60,000 ride") and I have seen how he leans, and the GPH his engine burns when just buzzing around locally. There is NO reason to doubt any claims he makes, and in his shoes, I wouldn't waste my time on a flight like you propose either. If you can't take his word for it, that would be your problem. It can be debated all day, but it is really simple:

ROP is cooling with fuel
LOP is cooling with air

Fuel = $4/gal
Air = Free

Debate all you want, but these are the facts. You argue that the gains that are made are simple a matter of running lower power settings. As mentioned above, our Cardinal with 180HP O-360A1A can be run at Peak running lower than 18" MP and 2500 RPM, but still the best FF's I can get out of it are about 7.5GPH. If Dan can run his bigger engine, at the same power settings LOP and get lower FF's, LOP has benefits over even running at peak. So simple an effective test would be this. Take another 200HP angle valve RV-7 with similer performance as Dan, and fly side by side on a short trip, one at peak or as close as it can be ROP at 55% power, and dan LOP at 55% and see who burns more. Much simpler than your proposed flight, and would prove much more.

But in the long run, whose out to prove anything? Obviously you don't believe it, and I've seen it with my two pairs of eyes and I believe it. GAMI/TATI swears by it, most of the Cardinal RG guys use it, and I run as lean as I can in the Carb'ed airplanes I fly. I believe in LOP, YMMV.

As with Dan, i'm done with this thread.

 

[Yukon]

LOP Challenge

Stephen,

Good for you! I remember the guy that gave me my first RV ride, and I'd back him word-for-word too when he talked about RV's. No doubt Dan is a good man, and I really like him too, but just as you "called out" Mr Brown on
his backfiring statement in the Ryton sump thread, I have issues with LOP.

So I renew my challenge, this time to the entire LOP RV community. Bring me proof to Phoenix, Arizona that Dan's claim of 35 mpg at 170 MPH is sustainable in an 0-360, and I will buy your gas and your lunch.

John

RV-9 QB / O-235

 

[Yukon]

Smoking Dope

Milt,
See, that's what really bothers me. You accuse the Austrailian Board of Transportation of "Smoking Dope" when they find against aggressive leaning,
as does Deakins. Lycoming, of course has to be nuts too, according to all accounts here on the forum. Even Flying Magazine is tainted, if you listen to Deakins.

Have you ever heard of a fixed-pitch airplane achieving these incredible claims? Sure, 15% is easily achievable by normal leaning techniques, but 35
MPG???? Doesn't that make you wonder, Milt? What is your theory on this?

Call it what you want, but when a FP airplane starts to loose RPM from fuel starvation during aggressive leaning, it is a fast, obvious process of increasing angle of attact and slower rpm. "Step" is what a well-trimed, balanced cruise was called at one time, and I think you know that.

I find this topic very interesting, and I think it is worth our time to quantify the gains of LOP. What's your best MPG????

John

RV-9

 

[dan]

So I renew my challenge, this time to the entire LOP RV community. Bring me proof to Phoenix, Arizona that Dan's claim of 35 mpg at 170 MPH is sustainable in an 0-360, and I will buy your gas and your lunch.

I'm not interested in lunch, and I don't have an O-360 anyway. http://www.rvproject.com/20060419.html If the photos aren't proof enough (I don't blame anybody for doubting the integrity of "an instant in time" photos from some unknown individual on the web), then ok, no big deal. Don't believe the hype.

Yukon, there's no pleasing you. You argue with everything, both here and on the SoCal list. I don't remember seeing much of a positive "contribution" from you on any of these forums other than doubt and contradiction, coming from a perspective of NOT having had experience with these domains. Maybe I missed it or your tone of doubt overshadows whatever nuggets of wisdom you may have shelled out. The question you need to ask yourself is: "How am I helping?"

 

[Yukon]

LOP Challenge

Dan,
I'll ignore the personal attacks, and ask again......

Where's the Beef?????

John

 

[N395V]

Where's the Beef?????[/

Ok let's try one more time. My theory on this is>>>>>>>>>>>>>>>>>>>>


Agressive leaning does not equate to LOP

The purpose of LOP is not solely to increase MPG although that is a nice result.

If you look at the earlier graph you will see that there is a point on the lean side where BSFC peaks. At that same point the down slope of the CHT and the Down slope of the ICP is significantly steeper than the down slope of horsepower.

No body is claiming magical numbers that equate to a free lunch. What we are suggesting, based on proven fact is that there is a confluence of the performance curves on the lean side of peak that:

#1 decreases Intra cylinder pressures in greater than linear proportion than it decreases available horsepower thus suggesting prolonged engine life.

#2 decreases CHTs and EGTs in greater than linear proportion than it decreases available horsepower thus suggesting prolonged engine life.

#3 decreases fuel consumption per horsepower produced in greater than linear proportion to a decrease in available horsepower thus decreasing fuel consumption or increasing MPG.

At this same horsepower setting on the ROP side the CHTs ICPs EGTs are all significantly greater as is fuel flow.


No one is suggesting that you lean so aggressively that the engine is on the verge of stopping., or that you have decreased horsepower to the point that a fart in the cockpit stuns your fixed pitch prop into silence.

LOP operation is a process of fine tuning your engine so that all cylinders are operating on nearly the same curves for CHT EGT ICP and then finding a spot on that curve that decreases the stresses inherent in internal combustion engines, while providing acceptable power to perform the task at hand.

If you are leaning a fixed pitch prop to the point that the plane destabilizes in minor air currents you are not running LOP you are leaning too aggressively.

No one who investigates the subject is saying Lyc or Cont are stupid. Both organizations have recognized that their engines run just fine on the lean side.
Lyc and Cont rec ROP because they realize that most pilots will not properly tune their engines nor instrument them to find the proper point on the lean side of peak safely.

As far as being a Deakin fan I admit I am unabashadly a big time Deakin fan, primarily because he is usually right and backs up his conjecture with documented fact or experimental data which is more than can be said for the Aussie investigatory board who present no solid evidence to support their conclusions. Yet many blindly accept their finding as fact. I would not accept outrageous theories even from Deakin if they were just speculation, innuendo, or a continued propagation of OWTs.

The following is a quote from Bob Nuckolls that I find particularly suitable to the discussion of LOP. The words in red are mine.

< What is so wonderful about scientific truth...is that >
< the authority which determines whether there can be >
< debate or not does not reside in some fraternity of >
< scientists;nor does it reside in some fraternity of the uninformed purveyors of old wives tales, nor is it divine. The authority rests >
< with experiment. >
< --Lawrence M. Krauss >

 

[Yukon]

Fixed Pitch LOP

Milt,

Appreciate the civilized post, and I agree with alot of what you are saying.
Now........please address my question. Why are fixed pitch installations not able to benefit from LOP, beyond typical leaning gains? Have you noticed that nobody has responded to the Canadian gentlemen in this regard?

John

RV-9 QB

 

[hevansrv7a]

Ok let's try one more time. My theory on this i

#1 decreases Intra cylinder pressures in greater than linear proportion than it decreases available horsepower thus suggesting prolonged engine life.

#

Horsepower is a function of BMEP - Brake Mean Effective Pressure, displacement, and RPM. MEP = 150.8 x (Torque / CID). Is there something about the difference between peak pressures and MEP that is caused by LOP?
If not, #1 cannot be true, by definition. Otherwise, an excellent post IMHO.
h

 

[dan]

Where's the Beef?????

The "beef" is currently up in NorCal. Flew up here yesterday, LOP. Flew today, LOP. The beef is flying around putting theory into practice, visiting family and traversing the continent in a very economical mode.

If I had all the time in the world, I might consider humoring your request and flying to AZ to prove things to you, the one person (at least one of the few really vocal ones) who thinks the claims are just claims. But I don't have all the time in the world. Got stuff to do, places to fly for FUN and not just to prove somebody right or wrong.

On a slightly related note, about a year ago I wanted to get together with Robert Paisley and do some side-by-side performance tests. Not to see who is faster (he's got that one covered), but to build a spreadsheet with lots of data on real-world fuel burn at a few different airspeeds & climbs/descents to compare our setups...for builders to make an educated decision about which "profile" serves their mission best.

Robert and I planned on doing it, but it never transpired. Know why? Because we're so darn busy enjoying what we're doing. There are too many fun things to do in every day and just not enough time. And it comes down to: "how would it be helping?" I no longer feel compelled to do this "challenge" thing. Even though I didn't choose to put a Subaru up front on my RV-7, I have the utmost respect for people like Robert who are honestly, truly, tangibly contributing to the sport. Putting his own time and effort into making other people's lives easier. Adding options, not narrowing them down. And the last thing I want to do is pressure Robert into taking time away from what he's doing (developing new engine adaptations!) just so we can have this little spreadsheet thing. In the grand scheme it just doesn't "help" enough to bother doing it.

I see this "LOP challenge" as very similar, but I see it as serving even less purpose for the community. It's not like we took a vote and hundreds of people want to see this data and are hinging major powerplant decisions on the results. I understand where Yukon is coming from. He doesn't believe the claims. He is skeptical that LOP is not detrimental to our engines. I don't blame him! You can't believe everything you read, especially on the internet. Healthy skepticism is a good thing. I don't know if I necessarily would have believed it until I did it, either!!

 

[Yukon]

No Time

Dan,

Don't get me going! You know and I know that there will never be a Subaru flyoff. Van has asked them numerous times and nobody seems to show up at the factory with one. Sure, I'm busy too, but if I had a clearly superior aircraft, I would make time to show it off. The 4 cyl doesn't make rated power, the 6 runs hot as a pistol, and the new gearbox has 12 bearings!!!As you know, this is my other "hot button". A great example of why I become aggrevated on the forums.

Glad you are having a good time with your airplane. Got my panel in from Affordable Panels. I'll send you a picture this week.

John

RV-9 QB

 

[Yukon]

No Free Lunch

Horsepower is a function of BMEP - Brake Mean Effective Pressure, displacement, and RPM. MEP = 150.8 x (Torque / CID). Is there something about the difference between peak pressures and MEP that is caused by LOP?
If not, #1 cannot be true, by definition. Otherwise, an excellent post IMHO.
h

Good job! This is the mathmatical model of my "There is no free lunch in Aviation" assumption. It also explains why a fixed pitch engine rolls back when leaned to LOP.

John

RV-9 QB

 

[Captain Avgas]

Happy hour

Good job! This is the mathmatical model of my "There is no free lunch in Aviation" assumption. It also explains why a fixed pitch engine rolls back when leaned to LOP.
John
RV-9 QB

There may be no free lunch but there's definitely a happy hour.... and after all, it's cheap juice we're after.

But, on a serious note. Charles Lindbergh employed LOP technique to navigate the Atlantic. Towards the end of the propellor airliner era LOP operations were standard corporate practice on the large supercharged and turbocharged radial engines such as the Lockheed Constellation and the Douglas DC-7. Were these people all misguided fools. Are you suggesting that on all of those long trans Atlantic flights no-one ever bothered to calculate whether they were actually getting better fuel consumption by running LOP.

The Brake Specific Fuel Consumption (BSFC) on the rich side of peak will always be higher because that's the side where you're pissing out the unburnt fuel through the exhaust....it's too rich to be fully converted into energy. Now is that so hard to understand.

 

[N395V]

Horsepower is a function of BMEP - Brake Mean Effective Pressure, displacement, and RPM. MEP = 150.8 x (Torque / CID). Is there something about the difference between peak pressures and MEP that is caused by LOP?
If not, #1 cannot be true, by definition.

Thank God civil discourse backed up by fact and logic.

Your math and logic are correct and impeccable however unless I am mistaken the formula yields a straight or nearly straight line. If the actual pressure curves were pyramidal or trapezoidal mean effective pressure would have a direct relationship to peak. However these curves are more parabolic and require (I think) a derivative to relate peak to mean. Now I am no mathemetician and may be wrong.

The curves I reference are actual pressure, temp measurements taken from an engine on a test stand, the bsfc is a calculated wave form derived from measured fuel flow and massaged with measured BHP (If I remember the Church of ADA seminar correctly) So I think my difference between theory #1 and your calculation rests in the precision of relating peak to mean using derivatives as opposed to what appears to me to be a linear formula. With the added effects of actual measurement as opposed to calculation.



It is refreshing to have a response in this discussion supported by fact, science and thought. It gives me something to consider and think about and certainly helps others in the understanding (or lack of understanding) LOP.

Thanks

 

[N395V]

Good job! This is the mathmatical model of my "There is no free lunch in Aviation" assumption. It also explains why a fixed pitch engine rolls back when leaned to LOP.

John

RV-9 QB

Actually John,

That is HEVANSRV7A's mathematical model for why a portion of the theory behind LOP doesn't provide a lunch. And I must say it gives pause for thought and requires more discussion as to why than I have given it above. However as mentioned above over and over and more succinctly in a recent post there does appear to be "happy hour".

As someone else mentioned the engine does not know it is a 4 or 6 cylinder and does not know what kind of prop it has.

You seem to think in extremes, black and white, full rich or idle cutoff. This is a discussion of the subtleties of the in between.

Clearly no one can convince you of the benefits of LOP. What separeates you from those of us who believe in LOP is that when presented with fact rather than bluster we can be persuaded that we might be wrong.

You have done nothing to weaken my belief in LOP. HEVANSRV7A has given us something to think about.

I do not recall seeing many posts by you on the matronics rv forum, there are many there that share your thoughts and style I am sure you would be welcomed as a regular contributor.

 

[rvatornate]

Dan,

Don't get me going! You know and I know that there will never be a Subaru flyoff. Van has asked them numerous times and nobody seems to show up at the factory with one. Sure, I'm busy too, but if I had a clearly superior aircraft, I would make time to show it off. The 4 cyl doesn't make rated power, the 6 runs hot as a pistol, and the new gearbox has 12 bearings!!!As you know, this is my other "hot button". A great example of why I become aggrevated on the forums.

Glad you are having a good time with your airplane. Got my panel in from Affordable Panels. I'll send you a picture this week.

John

RV-9 QB

Perhaps you should stay aware of what is happening before making sweeping statements like " There will never be a Subaru flyoff" One was just done at Van's in the past couple of days with one of Eggenfellner's older 2.5 supercharged. Check out Egg's Yahoo group, or I'm sure someone will post it here shortly.

 

[RVbySDI]

Perhaps you should stay aware of what is happening before making sweeping statements like " There will never be a Subaru flyoff" One was just done at Van's in the past couple of days with one of Eggenfellner's older 2.5 supercharged. Check out Egg's Yahoo group, or I'm sure someone will post it here shortly.

Duely posted. http://www.vansairforce.com/community/showthread.php?t=7796

 

[Yukon]

Actually John,

That is HEVANSRV7A's mathematical model for why a portion of the theory behind LOP doesn't provide a lunch. And I must say it gives pause for thought and requires more discussion as to why than I have given it above. However as mentioned above over and over and more succinctly in a recent post there does appear to be "happy hour".

As someone else mentioned the engine does not know it is a 4 or 6 cylinder and does not know what kind of prop it has.

You seem to think in extremes, black and white, full rich or idle cutoff. This is a discussion of the subtleties of the in between.

Clearly no one can convince you of the benefits of LOP. What separeates you from those of us who believe in LOP is that when presented with fact rather than bluster we can be persuaded that we might be wrong.

You have done nothing to weaken my belief in LOP. HEVANSRV7A has given us something to think about.

I do not recall seeing many posts by you on the matronics rv forum, there are many there that share your thoughts and style I am sure you would be welcomed as a regular contributor.

Milt,

You know Milt, even as your theories are crumbling, you continue to attack me personally, although in a more muted tone. Heavansrv7 's mathematical
representation of my fixed pitch propeller question will only be understood by engineering types such as yourself. The other 95 percent of this forum will read my posts and think. "hmmm, I wonder why a fixed pitch prop won't maintain rpm in LOP" It might strike them 2 weeks later, but sooner or later they will get the insight that gasoline is the root of all horsepower.

Your contention that "the engine doesn't know hat kind of a prop it has " is simply rediculous! Who "knows better" than the machine exerting the rotational energy that the prop is not changing to a lower pitch?

Yes Milt, my tone can be a little abrupt, but certainly no more so than your's or Dan's when you guys start hurling insults. Give heavansrv7 the credit if you must, because its good enough for me just to be in the same room when Milt catches a clue!


John
RV-9 QB

 

[Yukon]

Subaru Smack Down

Perhaps you should stay aware of what is happening before making sweeping statements like " There will never be a Subaru flyoff" One was just done at Van's in the past couple of days with one of Eggenfellner's older 2.5 supercharged. Check out Egg's Yahoo group, or I'm sure someone will post it here shortly.

Guilty as charged! Isn't that just the way things go??? I beg for Subaru performance numbers for the two years it takes me to make my engine choice, and the day I make a post like that the flyoff happens! True it's a supercharged motor, true it weighs 105 lbs more, but at least we finally have some numbers.

Nathan, I don't want to detract one small bit from the happiness you get from your airplane, because I know you guys love that little Subie! Everybody has the right to install exactly what they want on their airplane. But had I bought that engine like I almost did, and achieved that kind of performance,
with that much weight ,complexity, and temperature issues, I would be absolutely furious with Jan and all of the people that have conspired to conceal it's performance shortfalls from the buying public. I believe that engine first flew in 1997. It has taken 9 years to get that installation to the point it can be out-performed by a non-supercharged Lycoming RV-9. It has actually taken so long to mature the concept, the engine is no longer being offered by Eggenfellner! There is an enviable product cycle! It even looks like the gearbox is about to be replaced by a belt drive model.

Having said all that, I do respect Jan for being innovative in a very structured and stodgy industry. However, he is finding out first hand why Lycoming has stuck with what appears at first glance to be antiquated technology.
IT"S LIGHT! IT"S RELIABLE! IT'S EFFICIENT! Not as smooth a a car engine, but then again, it's not a car engine........

John
RV-9 QB

 

[jcoloccia]

Wasn't the 2.5L Subie in question rated at 165HP vs 160HP for the Lyc? The performance numbers for both aircraft were very similar, differences in climb performance can be easily attributable to weight/flying skill/propellor, and the different speeds can easily be attributable to flying skill, propellor, construction etc. I'm not trying to be argumentative but if I look at the results objectively (as opposed to seeing what I want to see) I would have to admit that they seem well matched. Another way of saying it is that the results are inconclusive in terms of which engine performs better (although they are clearly conclusive in terms of which aircraft performs better...this is different).

It's not unheard of for a well built lower horsepower RV to outperform a similarly equiped higher horsepower RV of the same model.

 

[Yukon]

Subie Numbers

John,

I believe the Eggenfellner Subaru 2.5 is (was) marketed at 165 horsepower without a blower. The blower provides 34" of MP up to 14000 feet (approx).
The test Subaru plane had a blower, and to the best of my knowledge was said to produce 190 hp, up to and beyond 8000 feet. At 8000' Vans airplane
was only producing 120 hp, but outperformed the supercharged Subaru.

I know none of this makes sense, but the Subaru installation seems to suffer from severe cooling drag issues related to the poor placement of automotive
radiators in a stock RV cowling. Reduction gear losses appear to substantial also. There is a lot of friction generated when you spin an engine at 5000 rpm and it has to be paid for somewhere. Also remember that this is only a 150 cu inch engine, so where the expectation of 165 hp came from is beyond me. Had this little engine been marketed at 110 hp, like it really is, there would be alot more satisfied customers, and it might still be in production.

John
RV-9 QB

 

[pierre smith]

Subie no

Guys,
I've watched a close friend of mine complete his RV7 over the last year and a half with Jan's supercharged Subie 2.5. Granted we have a 180 Lyc but we also have a nosewheel and even without landing gear fairings or wheelpants, were 20 MPH faster than he was, side by side. Now with all the fairings, the difference is even greater.

He also told me recently that he only burned 7 GPH on a return flight from Memphis. My reply was that has to be because he's not making the horsepower. It takes a given amount of fuel per horsepower/hour but he's happy going along at 160 something. Furthermore, he NEVER pulls the throttle back from 34" but adjusts the prop to 2500 or whatever he wants to. Just how long will an engine last at WOT at all altitudes? I agree with an earlier post that the Subie installation has a tremendous amount of cooling drag, and the fact that it's rated horsepower must be lower than we think.

 

[Yukon]

Subie,NO

Pierre,

I am really astounded by the incredible bulk of intellectual dishonesty that comes out of the alternative engine community. By all means, install what you want, but don't compell others to do so under false assumptions. I came so close to powering my airplane with one, I shudder to think.

Thanks for sharing your speed and efficiency comparisons with the forum. There has been a sort of "performance black out" on this engine since I bought my kit. Speeds, weights and specific fuel consumption were virtually impossible to obtain. Now that it is out in the open, builders can make an informed choice on what they want to power their RV.

John
RV-9 QB LYC 0-235

 

[N395V]

your theories are crumbling

Not hardly

by engineering types

While I am not an engineering type I did recently stay at a Holiday Inn express. Now in all fairness to you, you would have had to go through the time consuming and difficult task of viewing my public profile to know that. I will however accept the compliment that you think I may be smart enough to be an engineer

when Milt catches a clue!

Yes when that happens it is a site to behold. I almost came in my pants when the light turned on and I realized that LOP offered some merit for consideration.

Who "knows better" than the machine

Reminds me of three elderly rednecks taking a test for their high school equivalency diploma.

They were asked by the examiner to name the invention that has had the most profound effect on society and why they think that.

Bubba stated penicillin and justified this based upon the lives it has saved over the last 60+ years.

Cooter listed the personal computer describing its impact on the efficiencies of our daily lives and its role in education, science and research.

Boo simply wrote the thermos bottle. The examiner somewhat perplexed asked him to explain his answer.

Boo said wellll duhhhh everyone knows you put in iced tea it stays cold, you put in coffee it stays hot. The examiner even more perplexed says so what is so special about that?
Boo now really agitated says to the examiner boy you be the dumbest person I ever did meet. The thermos just gots to be the smartest thing around to know when to keep stuff cold and when to keep stuff hot.

Cooter and Bubba paid attention to the 99% of people willing to engage in discussion and learned collectively.

Boo just clung to his old wives tales and chose to believe that which was convenient and agreed with his view of the world. When things didn't agree rather than gain knowledge and respond with reason he just continues to respond with a blustery negativism typical of the uninformed

continued to attack

Not even close. I have just been toying with you. While I am not an engineer I am a former Marine and if I ever elect to attack there will be no doubt in your mind or anyones that it is occuring and unlike watching me "get a clue" you will not want to be in the room.

 

[Yukon]

Now I Understand

AHHH, a Marine.......

You know what you call a Marine fighter pilot with an IQ of 160?????

 

[N395V]

AHHH, a Marine.......

You know what you call a Marine fighter pilot with an IQ of 160?????

Gifted

 

[Yukon]

Nope!

A Flight of Four!

 

[Ironflight]

Yukon,

Might I suggest that it is time for you to go back and read the rules of these forums, and then ask yourself if you are adhering to their spirit? Just a suggestion...

 

[Yukon]

Jokes are OK!

Just finished reviewing them. Thanks for the heads up!

John