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Lean of Peak

Thanks, Milt

N395V said:
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. I think you are right - h.

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.
Click to expand...
Thanks, Milt.
As you point out, BMEP can either be measured or calculated. I did not realize (sorry) that you had actual measurements. In either case, MEP or BMEP is an average or "mean". But you are right that not all curves are equal and that is what I was asking. So, your #1 means that the curve is flatter (more area under it) right? For the HP to be better while the pressure peak is lower can only happen if the curve is flatter. Now, correct me (anyone) if I'm wrong, but doesn't that implicitly mean a nice, even, long-lasting burn? That's exactly what I would expect from LOP, too. Because..

If you run LOP in a hypothetical perfect engine, you are assured that all the fuel will be consumed. (BTW - diesel engines use WOT and control power only with control of the amount of fuel injected.) That is clearly not true of ROP. When a given amount of fuel is burned, it requires a given amount of oxygen, which is present in air in a constant percentage. When you have that you have stoichiometric conditions which are fixed by chemistry and physics. In ROP there is wasted fuel. I will take a guess that best power and peak EGT will coincide closely, since it takes temperature to expand the gasses that drive the piston down and greater power thus requires greater temperatures if all else is equal.

LOP is not maximum power, since it must mean that for a given cylinder's volume and volumetric efficiency, extra air displaces some fuel, so you can't get maximum power from that cylinder while LOP. I believe, however, that for a given HP less than maximum, LOP is going to be more efficient in most cases.

BTW - some experts say that the rich mixture we use for operations >75% is not really cooling the engine, but retarding the timing. The math they present suggests that they are right in that there isn't enough wasted fuel to account for the cooling effect. I'm convinced, anyhow. That does lead to some interesting questions for the guys with electronic ignitions, though.

Yours for helping each other learn,
h
 
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Slow Burn

My turn to weigh in. I think the combustion engineers believe that the rich mixture (unburned fuel molecules running interferance or such) slows down the rate of combustion, rather than changing the timing. That, in turn, reduces peak pressures and temps to tolerable levels for our fuel. Why is that significant? The same result is obtained lean of peak - without the wasted fuel.

By the way, my company operates large (500 to 3000 horsepower) natural gas fired compressors, both 2 stroke and four stroke, and the most efficient, longest lasting engines run lean of peak. Turbo superchargers 3 feet across.
 
WOW! What a thread.

There is a fair amount of misinformation and confusion covering several topics in this thread covering carbureted operation LOP, Detonation and Pre-ignition, CHT targets, EGT limits, GAMI spread and it's effect on Hp and smoothness and effects of mixture on effective timing. There is no way to address all of those topics in one message, so I'm going to start new threads on each as a single topic so each topic can be specifically addressed.

If any of you are interested in one of those topics, please look for those individual threads in this same section. Thank you.

Walter Atkinson
Advanced Pilot Seminars
 
Walter Atkinson said:
WOW! What a thread.

There is a fair amount of misinformation and confusion covering several topics in this thread so I'm going to start new threads on each as a single topic so each topic can be specifically addressed.

If any of you are interested in one of those topics, please look for those individual threads in this same section. Thank you.

Walter Atkinson
Advanced Pilot Seminars
Click to expand...


It's about time you showed up Walter.

If you get a chance can you also offer some insight re pressure carbs and LOP?
 
Milt:

Pressure carbs tend to do a teeny bit better--maybe. It depends on the installation. They still have the vaporiation issue to contend with.

Walter
 
Risk / Reward

Hey Guys,

Here's some more food for thought. The upside of LOP according to GAMI is .9 to 1.5 GPH. About 3.75 to 6 bucks per hour savings. That's without considering the time and the cost of modifications.

The downside, no matter how small you or Walter estimate the chance, is quite steep. Detonation will ruin your day. Don't let anyone tell you different.
Whethter it comes as a result of miscalibrated instruments, broken spark plug insulators or just pilot inattention, bad auto gas, detonation is a bad deal.

John
 
Pressure carbs. I run 'em LOP all the time. Depends on the physical setup, I guess.

I have a Twin Bonanza, so I run two pressure carbs (GO-480 Lycomings) LOP, and it runs very smoothly.
 
Tom Gresham said:
Pressure carbs. I run 'em LOP all the time. Depends on the physical setup, I guess.

I have a Twin Bonanza, so I run two pressure carbs (GO-480 Lycomings) LOP, and it runs very smoothly.
Click to expand...

Pressure carbs are an enigma to me. Had an old old Twin Commander with GO480s that I would lean the **** out of and they ran fine. I am now putting an M14PF on a plane and it doesn't have a mixture control.

Seems dumping the carb output into the supercharger is a great setup for LOP.

Can I just put a valve on the carb fuel inlet and use it like a mixture control?
 
"Seems dumping the carb output into the supercharger is a great setup for LOP."


The original intent of the supercharger on the first radial engines in the 1920's was to provide even mixture distribution to all cylinders, not really for increasing power.
 
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Headwinds

It's a nod to the fact that LOP produces less power and less TAS, which becomes harder to accept when coping with low groundspeeds.

John
 
Prior to 1992 stomach ulcers were a leading cause of morbidity and death in most of the industrialzed countries in the world. It was also the single most frequent cause for surgery.

Everybody (especially physicians) knew ulcers were caused by stomach acid, worry,and spicy food. These were rock solid "FACTS" known to all through the ages.

In 1982 an Australian gastroenterologist noticed little pinhead sized black specs in the stomachs of ulcer patients
and suspected they were bacteria. He indeed proved they were bacteria and presented a paper at an international conference suggesting they caused ulcers. He was jeered and derided by his peers and was written off as a quack.


He went home and removed the bacteria from one of his patients and ingested them. He promptly got an ulcer. Instead of surgery he took antibiotics and the ulcer went away. He published this in a journal. The result was he lost his medical license for "practicing quackery"

12 years later he was proven correct and awarded a Nobel Prize for his discovery. Ulcer surgery is now a thing of the past.

In those 12 years tens of thousands died from ulcers and the complications of surgery, millions more suffered horribly.

If only physicians would have listened with open minds how much suffering could have been avoided.

Somethings are hogwash some are propwash. An open mind causes no harm. It pays to listen to fact rather than conventional wisdom. This applies to medicine, RVs and LOP.

History of Ulcers
 
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Facts

N395V said:
...

In 1982 an Australian gastroenterologist noticed little pinhead sized black specs in the stomachs of ulcer patients
and suspected they were bacteria. He indeed proved they were bacteria and presented a paper at an international conference suggesting they caused ulcers. He was jeered and derided by his peers and was written off as a quack.


He went home and removed the bacteria from one of his patients and ingested them. He promptly got an ulcer. Instead of surgery he took antibiotics and the ulcer went away. He published this in a journal. The result was he lost his medical license for "practicing quackery"

12 years later he was proven correct and awarded a Nobel Prize for his discovery. Ulcer surgery is now a thing of the past. ...
Click to expand...
Fascinating! I didn't know any of this. Thanks for sharing it!

Perhaps one day Dr. Hulda Clark's theories on the causes and treatments for cancer will be as accepted as the treatment for ulcers. http://www.drclark.net/

Back to LOP in a headwind - I can't quite figure out why LOP would not be ok in a strong headwind, unless it is as John suggested, that you want to run at max power in a strong headwind to get those last few knots.
 
"It's a nod to the fact that LOP produces less power and less TAS, which becomes harder to accept when coping with low groundspeeds."

Absolutely true, as it relates to normally-aspirated engines. The difference between running ROP and LOP is usually about five knots. LOP is slower. I have run very LOP in my Baron (now sold) and the T-Bone. I give up about 7 knots in them.

The difference in fuel burn depends on the size of the engine, of course, and can be 1 to 5 gallons per hour (per engine). Assuming 3 gph, at $4 per gallon, that's $12 an hour saved. What is given up is getting to the destination about 5 minutes later per hour traveled. Each pilot must balance the equation for him or herself.

It changes with turbocharged and turbonormalized engines. With those, you can get back the power lost through LOP operation (by adding back manifold pressure), and can, with proper equipment and knowledge, actually run the engine at higher power, with cooler CHTs and lower internal cylinder pressure than the oft-recommended ROP settings.

Specifically, I can fly much faster LOP than I can ROP behind my turbonormalized engine. All while burning less fuel.

It seems like magic to me. But then, science has always seemed like magic to the ignorant, and I'm definitely in that category on science stuff.
 
To prove that Rick Durden is a bozo and clueless on almost everything worldly, he has two friends, Walter and Tom. That oughta just about count him out of anything serious, intellectually. That and the fact that he's a U of Mich grad and that I'm an LSU alum. (And, they think they play football in the Big Ten! HA!! <g>)

Rick is a very accomplished pilot. He and I did our DC-3 training together. The man is good. We teach float-flying together every summer in Cubs on floats. He knows what he's talking about. He's a skilled writer and drinks single malt Scotch. I've tried to convert him to a good Southern mash wiskey, but he's a resistant yankee. <oh, well, he still thinks the North won the War of Northern Aggression.>

As for the headwind issue, he was making tongue-in-cheek giggles. That's ONLY true if you are already starting out at max range airspeed. If you are starting out faster than max range airspeed, you can extend range by slowing down--even into a headwind. If you are short on fuel reserve to the destination in normal cruise, speeding up will shorten your range! You need to slow down.

Max Range can be achieved by setting the engine up at BSFC(min) where it produces the most Hp per pound of fuel burned and then slow the airplane to max range airspeed. No one really wants to go that slow, so "speed up into a headwind, slow down in a tailwind" is seldom actually correct. It is true IF you start out at max range airspeed.

Basically, about 10-15dF LOP and the minimal MP/RPM needed to maintain max range speed is the answer to max range. Man, is it ever S L O W.

Repeated testing in numerous NA aircraft has shown that the difference in Best Power mixture and BSFC(min) above about 8000 feet is 3 knots airspeed for about a 3gph fuel savings. In the RV, it will be a little less fuel savings since most are using 360s. If one is losing more than about 3 knots, they are leaning further LOP than optimal. It doesn't hurt anything, it's just giving up performance.

Walter
 
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Helicobacter Pylori

Milt,
I'm impressed! The next thing you are going to tell me is we are going to stop using leeches!!!

John


N395V said:
Prior to 1992 stomach ulcers were a leading cause of morbidity and death in most of the industrialzed countries in the world. It was also the single most frequent cause for surgery.

Everybody (especially physicians) knew ulcers were caused by stomach acid, worry,and spicy food. These were rock solid "FACTS" known to all through the ages.

In 1982 an Australian gastroenterologist noticed little pinhead sized black specs in the stomachs of ulcer patients
and suspected they were bacteria. He indeed proved they were bacteria and presented a paper at an international conference suggesting they caused ulcers. He was jeered and derided by his peers and was written off as a quack.


He went home and removed the bacteria from one of his patients and ingested them. He promptly got an ulcer. Instead of surgery he took antibiotics and the ulcer went away. He published this in a journal. The result was he lost his medical license for "practicing quackery"

12 years later he was proven correct and awarded a Nobel Prize for his discovery. Ulcer surgery is now a thing of the past.

In those 12 years tens of thousands died from ulcers and the complications of surgery, millions more suffered horribly.

If only physicians would have listened with open minds how much suffering could have been avoided.

Somethings are hogwash some are propwash. An open mind causes no harm. It pays to listen to fact rather than conventional wisdom. This applies to medicine, RVs and LOP.

History of Ulcers
Click to expand...
 
Walter Atkinson said:
Basically, about 10-15dF LOP and the minimal MP/RPM needed to maintain max range speed is the answer to max range. Man, is it ever S L O W.
Click to expand...
Now that engine monitors (such as the AF-2500) snag GPS data and display MPG (or KPG), it's easier than ever to tweak your power setting for max range. No more mental math. Just reduce power until the MPG reading peaks.

About it being S L O W, sorta. In my airplane it's about a 20 knot reduction in true airspeed from WOT economy cruise to max range cruise. But that still translates to 140 KTAS or better...which ain't bad! :D
 
Dan:

If you discount engine efficiency, your method is correct. It can be exptended further by attaining BSFC(min) mixture, THEN reducing power. Try it.

I'm surprised that an RV has such a high max range airspeed. That's unusual. Do you have a number?

Walter
 
Walter Atkinson said:
If you discount engine efficiency, your method is correct. It can be exptended further by attaining BSFC(min) mixture, THEN reducing power. Try it.

I'm surprised that an RV has such a high max range airspeed. That's unusual. Do you have a number?
Click to expand...
The last "max MPG" test I did a month ago or so was at about 75F LOP, so I wansn't at BSFC(min) mixture according to what you're saying.

As far as numbers are concerned, I didn't get too specific with my testing -- I should have. In any case, here are the "results" of my testing: http://www.rvproject.com/20060419.html

Peak MPG was achieved at 15.0" @ 2250 RPM @ 75F LOP, 4.8 gph, 148 knots groundspeed (light & variable/quartering headwinds), 35.4 MPG. I have an Aerosport Power IO-360-A1B6 with a Slick mag timed at 21 BTDC and Lightspeed Plasma II ignition, Airflow Performance injection, Vetterman exhaust, and ram air.

I didn't test at any other altitudes (just 10,500' MSL, OAT 37F)

Next time I'll try 10-15dF LOP as you mentioned, and I'll do some 3-vector TAS stuff to nail down the no-wind TAS & MPG.

My RV-7 is straight and relatively clean. It is a slick airframe and the powerplant kicks butt.
 
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Dan:

Nothing like a little DATA, is there? <g>

My supposition is that as you leaned past BSFC(min) and lost power you slowed toward the precise max range airspeed. That would give you the result you observed. The result would be a tiny bit off of true max range. You could milk a bit more at BSFC(min) and lower the airspeed with rpm. That improves prop efficiency and is essentially free Hp. Max range:

1) BSFC(min) on the engine.
2) Optimum prop efficiency RPM.
3) minimum MP to achieve max range.

Shucks, we could drive! <VBG>

Walter
 
A little more data

Walter,
I'm really getting wrapped up in this stuff! I'm learning alot! Hope everybody will read this 2003 article on GAMI injectors from AVWEB. A very intersting piece about the virtues of Continentals and GAMI's, and what they do for 4 cylinder Lycomings.

http://avweb.com/news/reviews/182501-1.html

"As we reported in the November 1998 issue of Aviation Consumer, we also installed GAMIjectors in the IO-360-equipped Mooney 201 we owned. Although this smoothed the engine out a bit and made leaning less fussy, the normally aspirated Lyc didn't always run leak of peak smoothly. And even when it did, the airspeed loss was too great a tradeoff for under a gallon an hour of fuel savings. "

John
 
the airspeed loss was too great a tradeoff for under a gallon an hour of fuel savings.
Click to expand...
Nice find, a very informative article. I read it in its entirety and indeed found that your quote above is a true and correct quote directly from the article.
However....

The article is not an AvWeb article it is a reprint from the consumer and has an error or 2 which I consider insignificant. Your isolated quote suggests that the authors consider LOP of no value especially for the 4 cylinder Lycs.

Let me add some quotes from the article you left out. Remember these are quotes from an article YOU put forth to justify" your attitudes toward LOP.

even for a small-displacement, low-horsepower engine, the fuel savings are hardly trivial. Rich of peak, in mid-teens at 65 percent power, were truing 155 and 160 knots at between 11.3 and 11.8 GPH before we installed the GAMIjectors. CHTs occasionally high enough to require either slight richening or cowl flaps.

With the GAMIs installed, could lean to 9.5 GPH for true speeds in the 153- to 158-knot range, with significantly cooler CHTs and EGTs no need to open the cowl flap

Leaning further, cools the cylinders but also costs power and airspeed. further, we found we could run the engine at 8.8 GPH, yielding airspeeds in the mid-140s and an endurance of nearly 8 hours. With a stiff tailwind, that makes 1200-mile nonstop trips possible.

Besides lower fuel flow and cooling, we think the additional benefit of GAMIs is this greater endurance and range. Over the course of a five-hour flight, the lower flow yields 10 or 11 gallons of gas that otherwise wouldn't be available in exchange for 3 to 4 knots slower cruise speed. (That's less than 10 minutes over the course of a five-hour trip.)

On many of our flights, this eliminates a fuel stop and the tedium of a 45-minute climb to altitude and descent at the fuel stop, this can shave a couple of hours off a long trip. Owners of large-displacement engines enjoy even more fuel savings and endurance benefits because they're starting out at higher fuel burns and carry more fuel than an aircraft with a smaller engine.

So are GAMIjectors must-have mods? For all Continental fuel-injected engines, we think the argument for installing them is compelling, especially for turbocharged models. GAMI's claims are clear and actually somewhat modest: With GAMIjectors, says the company, the fuel/air ratios will be balanced and your engine will run better. Other benefits accrue to include more consistent leaning and thus fuel savings.

We think the product delivers on this claim. However, results will be most dramatic in turbocharged and even some of these will respond better than others. GAMI tells us because of airflow shortcomings in the IO-520?WB TCM engines used in some Baron and the ?NB models found in some Cessna twins, lean- of-peak operation isn't always doable in these engines. They still benefit from smoother running and more efficient leaning on the rich side of peak, however.

We think seizing on whether the engine manufacturers approve lean-of-peak or not misses the point, for neither Lycoming nor Continental have published convincing recent research on this subject. GAMI has done the research, extensively, but in our view, the proof is in the operational experience.

Lean of peak is undeniably a fuel saver, EGTs, CHTs and **** are cooler and there's simply no engineering data to support the claim by many that lean of peak operations -- if done correctly -- will damage engines. There is, on the other hand, growing anecdotal evidence that engines run lean of peak show less valve and cylinder wear than those run rich of peak.

We are convinced that if done properly, there's no conceivable way that running an engine lean of peak can cause damage. The data simply doesn't support that lean of peak is, of itself, damaging
 
Lycoming VS Continental

No Milt, I left out nothing. If you will read my post again I acknowledged the significant gains on the (Continental IO-360) in the article ( although only accomplished after a trip to the GAMI headquarters in Ardmore, OK). For those of you unfamiliar, it is a tubocharged, injected, 6 cylinder Continental.

My quote was specificly in regards to Lycoming 4 cylinder engines, as tested on a Mooney 201, the one that 98% of us install in our RV's, and supports my origonal contention of minimal gains for this group.

Seems Milt that these mods were developed for the 6 cylinder Continental to correct the fuel flow imbalance inherent to a runner-type injector system, and only specific models of Continental. If you will read the website, you will see there are even some models of Continentals that won't support LOP operations effectively (some IO-520's)

Thanks for your participating though Milt!

John
 
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Walter Atkinson said:
My supposition is that as you leaned past BSFC(min) and lost power you slowed toward the precise max range airspeed. That would give you the result you observed. The result would be a tiny bit off of true max range. You could milk a bit more at BSFC(min) and lower the airspeed with rpm. That improves prop efficiency and is essentially free Hp.
Click to expand...
As of today I'm working with Don Rivera from AFP to experiment with my injector nozzle restrictors a bit. Everything is pretty much dialed in already from my perspective (sync'd EGT curves for LOP and very smooth, balanced, economical operation), but Don believes there's even more economy to be had -- by using smaller restrictors, which should improve atomization.

I was hesitant at first to mess with a Very Good Thing(tm), but I think I'll tinker a bit as my schedule allows. I'm running the stock .028" restrictors at the moment. Once I get the new restrictors, it may take a round or two to get it balanced again, but as time & schedule permits I'll play with it.

You can be sure I'll post my findings if anything significant happens.

In the meantime, Walter, maybe you can enlighten me as to how I can determine if I'm running in the following configuration:
1) BSFC(min) on the engine.
2) Optimum prop efficiency RPM.
3) minimum MP to achieve max range.
Click to expand...

Last time I just picked an RPM (about 2250-2270), leaned it about 75F LOP and went from there. You mentioned 10-15F LOP would be more efficient, so I can try that. Is there an easy way to determine optimum prop efficiency RPM in flight? I assume there's a relationship of some prop blade constant(s) to CAS or TAS and air density or some such? Most of this type of thing is over my head.
 
Dan:

Nozzle restriction is not the optimum answer to better atomization. Increasing the upper deck pressure to the injector is the answer. It's easy on a TC'd engine and not so easy to do on a NA engine. THAT will make the fuel come out in a fine mist fog... very "atomized!" Call me if you want to discuss options on achieving this.

The goal of F:A balance is not even EGTS. It is having all of the cylinders reach peak EGT at the same FF.

The BSFC curve peak shifts toward and away from peak EGT based on the power setting. At low power settings, it is around 15dF LOP. Set that FIRST.

The optimum RPM for prop efficiency can be attained from the prop manufacturer.

Walter
 
Walter Atkinson said:
Nozzle restriction is not the optimum answer to better atomization. Increasing the upper deck pressure to the injector is the answer. It's easy on a TC'd engine and not so easy to do on a NA engine. THAT will make the fuel come out in a fine mist fog... very "atomized!" Call me if you want to discuss options on achieving this.
Click to expand...
Right. The goal by reducing the restrictor orifice is to increase pressure at the injectors, thus improving atomization. We're saying the same thing using different words, I guess.

The goal of F:A balance is not even EGTS. It is having all of the cylinders reach peak EGT at the same FF.
Click to expand...
Trust me, you're preaching to the choir. Terminology is the enemy here. I don't use the term "EGT spread" because that implies a numeric delta among the cylinders' EGT *values*. I haven't come up with a term that I'm happy with to express what we're both saying. I guess we have to spell it out every time. Somebody please invent a term for this...does "balanced injectors" convey the concept properly?
 
RE: The article on Avweb, from Aviation Consumer. Note that it was in 2003.

Berto was so unhappy with Gamijectors that he gave the company the Gear of the Year Award in 2004.

Applicable copy follows:

--------

COMPANY OF THE YEAR: GAMI/TAT/APS
From time to time, our top editorial award goes not just to a product but to a company which we think best represents the ideal way of doing business in the rough-and-tumble world of general aviation, where making a buck is sometimes like squeezing water out of a rock. It?s difficult to do it at all, never mind do it well.


George Braly, left, at the Carl Goulet engine test facility in Ada, Oklahoma; sophisticated research available to aircraft owners.
One organization that we think sets a laudable standard is really two companies under the same roof: General Aviation Modifications, Inc. and Tornado Alley Turbo. GAMI, of course, is best known for its line of balanced fuel injectors (GAMIjectors) which tame the rumbles and burps in fuel-injected engines and pay for themselves by making workaday aircraft powerplants smoother and more economical.

As we reported in the April, 2004 issue of Aviation Consumer, Tornado Alley Turbo, which shares the same Ada, Oklahoma hangar with GAMI, builds well-engineered turbonomalization systems that we consider state-of-art. Although expensive, TAT?s products deliver impressive performance and customers rave about them.

But that?s not the driving reason we have picked GAMI/TAT as our company of the year. Knowledge is the real reason. George Braly, the engineering prime mover at GAMI/TAT, has done more to advance the understanding of how aircraft engines convert fuel into power than anyone we know. Heretofore, that knowledge either didn?t exist or was too closely held by the engine manufactuters to be of use to pilots and owners.

Through the Advanced Pilots Seminar programs, another GAMI-allied organization formed along with John Deakin and Walter Atkinson, this knowledge has now been placed on the table for all to see; think of it as direct pipeline into one of the most sophisticated engine research facilities on the planet.

Although not everyone agrees with GAMI?s engine operating doctrine, we think that?s really beside the point. The company?s research has made the information plainly available without prejudice; anyone can judge its merit. And in our view, that merit is considerable and well deserving of our company of the year award.
 
Hmmmmm....

COMPANY of the Year :

GAMI/TAT/APS.........Hmmmmmm


Tom,

Have you noticed, that with one notable exception, all the GAMI testimonials are coming from turbocharged 6 cylinder Continentals???? Have you noticed that none of these engines are used in (most) RV's. GAMI themselves have
ackowledged that gains are minimal for our engine. I'm loosing the plot here.

John
 
"I'm loosing the plot here."

Could be.

Some quiet time spent on the GAMI site will reveal (TADA!) that they say that some engines respond better than others to using Gamijectors.

And . . . they offer a money-back guarantee. Don't like the performance? Send 'em back.

Even after they tweak the nozzles and work with you on getting the adjustments right, you can return them.

Also, GAMI is known to tell airplane owners they don't need the injectors. If you send them a GAMI test with your current engine, and the data shows that your engine already has good fuel distribution, the folks in Ada will tell you to save your money. Not uncommon at all.

But, back to your question. The thread is in exploring. Experimenting, if you will. Learning. The knowledge is worthwhile and useful. The techniques may or may not be useful to each pilot.

The thread is that much of what has been taught and learned over the last 40 years is just flat wrong, or at least, it is incomplete. Probably two generations of pilots have been taught that there is only one half of the mixgtujre sweep chart. For them, the chart starts at peak EGT and goes to rich. So, for them, when they say they are running lean, they are just running on the lean side of RICH of peak. They are not running lean, at all, but only on the lean side of the Rich side of the chart.

If you reveal the other side of the chart -- the part that shows LOP operations, you realize that all that noise about how running lean burns up valves, engines, buildings, forests, etc., is really about running at high power, on the rich side, but not rich enough.

What I don't understand, after talking to many pilots about this for several years, is why some of them feel so threatened by this information. That part is a mystery to me.
 
RV functionality

"Some quiet time spent on the GAMI site will reveal [snip] that they say that some engines respond better than others to using Gamijectors."


[snipped by dr] Will somebody please present some evidence of it's functionality in RV aircraft???



John
 
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Real World Rv

"You've told us over and over how well LOP works for Turbo Bonanzas. Will somebody please present some evidence of it's functionality in RV aircraft???"

Stock O-320 in RV6 burns at least 1.5 GPH less fuel with 30-50F lower CHT & loss of 3-5KTS
 
John:

[snipped by dr]

Why do you think that an aircraft engine in an RV is different from an aircraft engine in another airframe?

Surely the cylinders, pistons, etc., don't know the difference.

I might be able to craft my answers better if I knew what it is about this data that troubles you so.

Tom Gresham
 
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Will somebody please present some evidence of it's functionality in RV aircraft???
Click to expand...

Well John,
It appears Dan has applied it fairly well to his 4 banger 360 and Bob M has done it with his 4 banger 320. I believe you have said that covers 95% of the RVs. That of course leaves out the RV 10s that use the same engine I have, a 6 banger 540. I do pay attention to everybodys posts that have something positive to contribute. I have had a helluva time getting my 540 to behave LOP. Much more so than with my Cont 520Ks, so I pay a lot of attention to the posts that have ,as you put it, the beef.

Below are my latest results (the beef) from a trip to Harlingen Texas recently.


Running my normal cruise settings at altitude of WOT and 2100RPM doing the GAMI spread I obtained the following information.

lopvaf3br.jpg


Now I shouuld have made .2GPH reductions but I am rather impatient so I did .5gph reductions.

The table suggests I am not quite there and my spread at peak is approx 0.7 GPH. I have gotten this far without GAMIs or tuned nozzles, just from reading and listening to Walter and others and swapping around stock injectors.

My HP and %HP may not seem to box and if so it is because at and below peak they are FFx14.9 and above peak they were done on a Lycoming whiz wheel. Even though the engine gets rough at 8.2 GPH with a big hit in TAS I can still run at 8.5 GPH, be within Lycomings acceptable limits for this power setting, and save 2.5 GPH from where I would run ROP, while sacrificing only 7 KTS TAS. I expect 1 more iteration on the nozzles will give me a 3gph saving at a 7-8 Kt loss. This with CHTs in the 330 or less range.

Now for the flight I made, this represents a trip time of 2hrs and 42 minutes LOP 2hrs 37 minutes ROP. A whole loss of 5 minutes. On the other hand at a 2.5gal per hr saving it gave me an extra 6.25 gal at trips end. Thats an extra 45 minutes of safety margin should weather close or winds increase.

And fuel savings are not the only reason we do it.

Now there you have it Lyc 320s, 360s' and 540s. All RV engines. I believe we have shown you in actual practice the functionality of LOP in RVs and similiar aircraft.

Now if it seems we do not lend credence to your thoughts and comments it is because you continue to try and convince, us and others, that we cannot possibly do what we are doing , yet we are doing it and our findings are consistent with each other and with what Walter and GAMI espouse.

Now of course we all could be fabricating our findings and lieing through our teeth but I for one have no intention of filming my next flight free lunch or not. Take it or leave it.

Walter and others comments or recommendations are welcome.
 
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As an aside to the above post I used to have terrible CHT problems in my Rocket. 400deg+ in climb 380deg+ at cruise. Had to run 13.5 GPH just to keep #5 and #6 below 390 in cruise.

Based on a lot of input, posts, and PMs from VAF forum members I have made some significant changes to my baffling and with LOP now climb well below 370deg and cruise with all cylinders below 360 at significantly reduced fuel flow. Most of this improvement was from baffling but I am crossing the finish line with LOP. So thanks for all the help.
 
Milt said: "Thats an extra 45 minutes of safety margin should weather close or winds increase."

Excellent point. More important than the dollars saved, in many cases, is stretching the range, or building more cushion for unexpected weather changes.

It's a good feeling to have extra fuel when you need it.
 
4 cylinder Lycoming

Tom Gresham said:
John:

Why do you think that an aircraft engine in an RV is different from an aircraft engine in another airframe?

Surely the cylinders, pistons, etc., don't know the difference.

I might be able to craft my answers better if I knew what it is about this data that troubles you so.

Tom Gresham
Click to expand...
[snipped by dr] Curious is the word that comes to my mind.

Data, what data? 99% of the discussion here centers around turbocharged Continental engines. Bob's figures are great, haven't had time to study Milt's numbers, but I will. And like I told Dan, show me you can sustain 35 mpg and I will sell my engine and buy one like his.

4 cylinder data is what I am looking for. Be it a Mooney 201, a Cherokee 140 or what have you. No more turbocharged Continentals, that's all I ask.

John
 
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Rv Lop

I run LOP when appropriate for the following reasons:

Less plug fouling, less frequent cleaning
Cleaner belly
Less stress on bottom end due to lower peak pressures
Cleaner oil
Lower cumulative time at high CHT (reducing loss of aluminum temper)
Lower fuel consumption (I know, its not much on a lowly O-320!)
Greater range
Smoother operation - both high and low frequency vibrations
Simpler operation.

Based on everything I've read, that last point might be questioned. I've developed a somewhat unconventional means of operating. At least for non-TAT Bonanzas. I have established a fuel flow that is guaranteed to be rich of peak for takeoff and high rates of climb (9.5 gph) at my typical runway DA (7000 summer) and another that is guaranteed to be lean of peak at 8000 feet in cruise (7.5 gph). Both WOT numbers. Guaranteed by documenting fuel flows over a range of mixtures and operating conditions. Note that I cannot simply shove the mixture in for takeoff around here - rich to the point that I loose power.

On take off I set up the 9.5 gph fuel flow and I'm set. No need to wait for EGTs to stabilize, no need to fiddle. I know it will work and I won't run there long enough to burn a lot of gas or foul plugs. If I have long steep climb, I adjust for altitude every few thousand feet as described by my .2 rule below without worrying about hitting any particular ROP egt number. I just glance occasionally to make sure they are all running equalized and not out of range. Eyes on the road and ears on the radio.

Once away from the airport and ready to set cruise climb or cruise, but still in the busy or crowded part of the flight, I pull back to 7.5 gph. I add about 0.2 gph for every 1000 feet below 8000 feet and subtract .2 for every 1000 feet above 8000. I know it works, takes no time to set up, and keeps attention where it belongs.

I leave it like that until out of traffic and ready to establish cruise. I then get to play with the mixture and really tune things up to exactly 10, 50, or whatever LOP suits the flight, find a vibration free sweet spot, document fuel flows, basically play.

On descent I crank the mixture in to compensate for altitude as described above. The landing checklist includes a short burst of full throttle to set the mixture to 9.5 gph.

(As a side note, I've discovered a couple of instances of fuel delivery problems just before landing by this method. Could not get 9.5 gph. I would not have noticed it if I used the leaning methods at partial throttle taught by my CFI.)

Another indirect advantage of LOP operations is it forces you to balance fuel flows. For some reason, folks that typically run ROP don't bother. It offers a lot of advantages even if you never run LOP.

In aggregate, the little effort to balance fuel flows and run LOP seems worthwhile to me on an RV.

Maybe this is an argument that good instrumentation enhances safe operation rather than LOP but that is where it has taken me.

Duane Zavadil
RV6A
EIO-320
 
540 troubles

Milt,

Very interesting post. I know you don't put much stock in what I have to say, but since nobody else has chimed in, here goes!

Where do you get your expectation that a 6 cylinder Lycoming should run on
8.2 gph? At .5 fuel per horsepower per hour, 122 hp should be consuming no less than 10 gph. I flew 540's for years on various spam cans, and seems to me 10-12 gph is what I was burning. Seems my 250 Commanche did about 175 mph on 12 gph.

I'm no Rocket expert, so feel free to tell me how wrong I am, but the cowling I see in those beautiful pictures you posted today has about the same size inlets as the cowling on my O-235 cowl. Why does anyone have the expectation that a 6 cylinder high compression engine will function properly with such small inlets? I would think baffleing would be very critical.

What is your oil temperature in climb and cruise?

Did you build this airplane or buy it? Beautiful airplane!

John
 
Dan:

Reducing the nozzle orafice size and increasing the fuel pressue is NOT what I'm talking about. I'm talking about the upper deck reference AIR pressure that goes into the nozzle. Based on our experiences, that is what has a very large effect on atomization.

Walter
 
Walter Atkinson said:
Reducing the nozzle orafice size and increasing the fuel pressue is NOT what I'm talking about. I'm talking about the upper deck reference AIR pressure that goes into the nozzle. Based on our experiences, that is what has a very large effect on atomization.
Click to expand...
Gotcha. Well, since air pressure at the nozzles is something that I cannot easily control in my NA engine, I can at least attempt to control the other parameter (FUEL pressure at the nozzles). Don is interested in seeing if there's an improvement, and I don't mind experimenting a bit.
 
John:

**And even when it did, the airspeed loss was too great a tradeoff for under a gallon an hour of fuel savings. "**

The airspedd loss from Best Power to BSFC(min) above 8000 feet will be 3 knots for a gain of about 2 gph. This has been confirmed repeatedly in all kinds of aircraft and is compatible with the predicted results from calculations.

If one is losing more airspeed than that they are not leaning optimally. This is a common problem.

Walter
 
Yukon said:
I'm no Rocket expert, so feel free to tell me how wrong I am, but the cowling I see in those beautiful pictures you posted today has about the same size inlets as the cowling on my O-235 cowl. Why does anyone have the expectation that a 6 cylinder high compression engine will function properly with such small inlets? I would think baffleing would be very critical.

What is your oil temperature in climb and cruise?

Did you build this airplane or buy it? Beautiful airplane!

John
Click to expand...

John, opening sizes in cowlings are *way* more complicated than just allowing incoming airflow. In fact, there are some High Power applications that have very small openings. It's a tradeoff of cooling vs. cooling drag. Ever notice how small the openings are in the Reno racer - Nemisis NXT's. They run Turbocharged IO-540's.

Also, people who run "plenums" traditionally can decrease the size of the inlets due to the efficiency of their cooling. This in turn decreases the cooling drag and allows for 2-5kts faster speeds.

Least we get *way* off topic, cowlings, plenums, and inlet/outlet sizes are all about fluid dynamics, and are an entirely different science.

Oh, and yes, btw, Milt's F1 is a beaut! But I know what he's doing to replace it, and it will be an awesome machine as well..... but I aint telling... :)
 
Mechanism for getting to LOP?

Walter,

Thanks for dropping by. I always enjoy reading about this topic.

I've seen, but can't lay my hands on, a pretty simply method for getting to LOP. Sorta a "close your eyes" method.... I think it's called the "big pull". Last time I read about it, it seemed most who tried it, could repeat their results quite nicely vs. the labor intensive way of watching the engine monitor like a hawk.

I'm sure you've described it a million times, so you must have some "boiler plate" somewhere that you can cut and paste and save your fingers.

For those of us, just getting used to the concepts. Maybe a quick primer is in order? If you feel so inclinded, perhaps, this is justification for a "new thread"?

Anyway, if my memory serves me, you set up from climb to cruise, let your airspeed build, then you "pull the red knob, until you feel a slowdown (using your most sensative instrument in the airplane, your butt :)), and basically you are LOP"? Can't be that easy can it? I'll assume it means you have worked to get to a balanced F:A ratio prior?

Thanks in advance,
 
Dan:

Definitions:
The *DIF* number refers to the difference between the hottest and coldest raw EGT value.
The *GAMI-spread* refers to the difference in FF between the first and last to reach peak EGT during leaning.

Milt:

It appears that you have a left-right GAMI split. That is frequently solved by finding the induction leak that is the common cause. The process is invloved and includes a HiLO GAMIlean test. If you need help with that, let me know by private e-mail or call me and I'll be happy to help.

John:

The vast bulk of the research I have been involved with at the Carl Goulet Memorial Engine Test Facility has been done on Lycoming engines--not Continentals. The info we're discussing is more based on the LYCOMINGS. It aplies eqaully to the TCM engines.

All of the combustion technology I am discussing applies to only the following engines:

Briggs & Stratton
Chrysler
Ford
Franklin
General Motors
Harley-Davidson
Honda
Jacobs
Lycoming
Pratt & Whitney
Superior
Teledyne Continental
Wright Aircraft

The similarities FAR out weigh any of the very minor differences. That is a critical concept to appreciate.

Walter
 
Duane:

Well, your engine management method is just too simple and logical not to mention compatible with the laws of physics! How in the world do you expect anyone to follow your lead? <VBG> (It needs to be complicated and hard to understand and accomplish or it can't be good, right?)

Good on ya!

Nothing like success.

Walter
 
Racing machines

"John, opening sizes in cowlings are *way* more complicated than just allowing incoming airflow. In fact, there are some High Power applications that have very small openings. It's a tradeoff of cooling vs. cooling drag. Ever notice how small the openings are in the Reno racer - Nemisis NXT's. They run Turbocharged IO-540's."


Allan,

Not a great example here. Air racing engines blow up with startling regularity.
I'm very sure high temps are definitely part of the reason for this. We are talking about airplanes that are expected to transport people safely for the TBO life of the engine. Adequate cooling is a must.

Rv-8's have had temperature problems with 200 hp since day one. Manageable, but problemmatic. No doubt plenums and good baffleing play a role, as does inlet and outlet size.

John
 
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