W

Walter Atkinson

Well Known Member
There is much confusion over these two phenomena. They are not the same and do not always go together.

First, Detonation is the explosive auto-ignition of the end gasses AFTER the planned spark ignition event. Small pockets of F:A charge auto ignite ahead of the flame front and create a shock wave in the combustion chamber which travels at the speed of sound in that medium. The shock wave bounces back and forth at the specific frequency that matches that speed.

The cause of detonation is the combination of IAT, CHT, and pressure within the combustion chamber. When those factors combine to initate combustion above the retarding effects of the latency period of the fuel, detonation is the result. Contolling CHTs and pressure are the BIG factors in NA engines. Contolling IAT in a TC'd engine thru the use of intercoolers is a major factor in widening the detonation margin. Also, the octane of the fuel and the presence of lead is a major factor.

Surprisingly, detonation, in and of itself, is not terribly destructive. We have run an engine for 30 HOURS of light detonation, 3-4 hours of medium detonation and 30 minutes of heavy detonation with NO ill effects whatsoever. As a matter of fact, the engine was sent to be inspected by an independent third party and the response was, "Why did you want a tear-down inspection, this looks like a normal, healthy engine."

As it turns out, a little, occasional light detonation can actually be good for an engine as it tends to clean out the debries and carbon build up!

The issue is the effect that detonation has on spark plug ceramic integrity.

That leads us to pre-ignition. Pre-ignition is the initiation of the flame front BEFORE the planned spark ignition event. It is a normal flame front, just started too soon. As opposed to detonation where EGT is little changed, pre-ignition results in rapidly falling EGTs and rapidly rising CHTs. The Peak Internal Cylinder Pressures can get very high, very quickly and this can destroy an engine in seconds.

The most common casues of pre-ignition are a failed spark plug ceramic which over heats and acts like a glow plug, a helicoil tang sticking in tothe combustion chamber and on very. very rare occasions, a particle of glowing carbon deposit. The later is exceedingly rare, but is the source most often cited! Go figure?

The most common progression is for a detonation event (from inadequate octane or high CHT or high IAT) to progress to the point where a spark plug ceramic is damaged resulting in pre-ignition which destoys the engine. Detonation is frequently mis-identified as the cause of the destruction.

The comments above are a sumary of the information learned from detonation studies at the most advanced engine test facility in the world, The Carl Goulet Memorial engine Test Facility. FAA experts have come to see this first hand and are adjusting their understanding of these events as a result.

Walter Atkinson
Advanced Pilot Seminars
 
In response to Walters post, I strongly encourage folks to attend Walter, George and Johns Advance Pilot Seminar. It is a very interestng course held a couple of times a year and you will definitly learn a ton of useful information on engine operating techniques. Plus, if you attend the seminar in Ada, Ok., they feed you like KINGS. Some of the best Bar-B-Que around.

Allen
 
Detonation is good? (not that bad)

Walter Atkinson said:
"The cause of detonation is the combination of IAT, CHT, and pressure within the combustion chamber..............................Also, the octane of the fuel and the presence of lead is a major factor."

"Surprisingly, detonation, in and of itself, is not terribly destructive. We have run an engine for 30 HOURS of light detonation, 3-4 hours of medium detonation and 30 minutes of heavy detonation with NO ill effects whatsoever." (how did you cause detonation and how did you tell how much detonation was occurring?)

"As it turns out, a little, occasional light detonation can actually be good for
an engine as it tends to clean out the debris and carbon build up! Walter Atkinson"
Click to expand...
Thanks Walter, another interesting provocitive post. Detonation and Pre-
ignition are indeed two different animals, but related. Just there names say it
all, pre ignition is just that, early ignition, detonation is abrupt uncontrolled
instantaneous ignition.

A big reason for detonation you did not mention is TOO LEAN OF A
MIXTURE! You mention CHT or IAT(Intake Air Temperature ?) and fuel
octane causing detonation, which is also true.

I disagree with, "detonation is not terribly destructive". I beg to differ with all
do respect, not withstanding you "test". I would love to hear how you did
this test, what engine and how you determined it was light, medium or heavy
detonation. My question is why would you do this? For what reason?


From John Schwaner at Sacramento Sky Ranch:
Pre ignition - "heat" and "meltdown"
Detonation - "violence, explosiveness and destruction"

Detonation (can) causes pre ignition
"A dangerously lean air/fuel mixture burns with most efficiency, so much that
the insulating boundary layer also gets consumed and the flame front touches
the metal walls. At those locations, there is a dramatic rise in temperature,
high enough to cause subsequent charges of air and fuel to spontaneously
ignite resulting in multiple flame fronts. This is pre-ignition;"
John Schwaner, Sacramento Sky Ranch.

(Ref: http://www.sacskyranch.com/deton.htm)


If you are going to be a proponent of LOP (lean of peak) operations I think its
important to mention this.

You are a proponent of using Carb heat to "help" carburated engines uneven
fuel distribution. Carb heat affects (IAT) and can cause detonation.
Therefore engine manufactures advise not to use carb heat at high power.
From what you are saying you agree.

Detonation (if left alone) will cause piston and ring damage, top
ring groove wear, scoring, sticking rings, piston hole to complete engine
failure. It can cause rod bearing failure leading to lubrication failure. The
damage can be hidden.

(picture of detonation pistons damage: http://www.hastingsmfg.com/Service Tips/images/p25b.gif)

You MIGHT get away with a little, but to say it is beneficial, I don't get,
especially for an air cooled aircraft engine.

Detonation is OK, not that bad? Could you explain that. Why would you
want to even play around with this? What agenda does that serve. I know
your opinion is to lean aggressively. Pilot's following your procedures of
aggressive leaning and LOP operations, should know too lean causes
detonation!

Under 75% power detonation margins increase, but many are running high
Comp pistons and electronic ignition with 42 degrees BTDC timing. I would
caution anyone taking your advice and comments about an engine test
detonation test to be careful how that relates to them. A Lycoming with HC
pistons and EI may not be happy with lean mixtures. Your test (on a
Continental IO520?) may not relate. It's our engine and soft fleshy hind-end,
so I just suggest caution and conservatism in pursuit of a better gas milage.

Thanks George
 
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gmcjetpilot said:
A big reason for detonation you did not mention is TOO LEAN OF A MIXTURE!
Click to expand...
I don't speak for Mr. Atkinson, but he probably didn't mention it because it isn't true. When operating lean of peak EGT, the detonation margin increases as the mixture is leaned.

I think the notion that detonation is caused by too lean of a mixture stems from when we couldn't really operate lean of peak EGT, therefore peak EGT was widely considered our lean limit. The range between peak EGT and about 30-40 degrees rich of peak provide the least amount of detonation margin, leading to the popular notion that the more you lean, the closer you are to detonation. The truth of the matter is as you lean towards peak, you do get closer to detonation, BUT if you continue to lean past peak your risk starts heading back down again.

I also agree with Mr. Atkinson that pre-ignition is worse. It can move your point of peak cylinder pressure from its ideal location of around 15 degrees ATDC back to around TDC, causing damage that many people would diagnose as detonation.

Not that he needs me to agree with him, of course. But I am becoming a fan based on what I hear of the Advanced Pilot seminars.
 
Not my point but thank you

Joey said:
I don't speak for Mr. Atkinson, but he probably didn't mention it (lean mixture correlation to detonation) because it isn't true.

The truth of the matter is as you lean towards peak, you do get closer to detonation, BUT if you continue to lean past peak your risk starts heading back down again.
Click to expand...
You seem to contradict your self? If you read my post and Sacramento Sky Ranch refrence I think it says it all. My question was rhetorical, but thank you. From you quote you do agree and the "TRUTH IS" leaning toward peak EGT (rich side) can cause detonation. There was no mention of LOP operations in his post. I thought it important to point it out.

I understand if you (can) get an over lean condition the temperatures are lowered, as well detonation is not possible or likely. There is just not enough fuel. More important is if you are below 75% power the pressures are lowered, which also gives more detonation margin.

This thread was put forth as a general discussion of detonation/pre-igntion, but now I see the agenda is promotion of LOP operations. Dumb me :rolleyes:

My main concern was the "spin" on how detonation is not bad. IN FACT you agree with me, mixture can cause detonation from your quote. Walter did not mention this. It should be clear. A poorly done LOP operation can result in peak or near peak operations on the rich side. Seems obvious but to make it sound like you can't cause detonation with the mixture is of course wrong. The other part where detonation is OK, is just well, I disagree with.

I am not arguing with LOP operations at all and never said other wise. Walter does think wide spread LOP operations is possible with any carburetor 4-cylinder Lycs. It's not a matter should you, it's a matter of can you? (and still have smooth operations.) If you can than great, just so long all cylinders are on the LOP side with some delta from peak.

Again Detonation = Good, is not in my dictionary.

Thanks for the input, I think we agree, really; my poor wording may have messed you up. I AM NOT ANTI LOP! I am just saying its NOT practical for ALL, and if done poorly you can screw yourself and engine. Will Advanced Pilot seminars replace your engine if you blow a hole in your piston? I blew a hole in a piston, in an airplane over water. The metal goes into the crankcase and makes a mess. I was successful making a forced landing on a grass strip, thankfully. Stuff happens.

To say you did a 5 hour test and how detonation is OK, is misleading and could be dangerous if misunderstood. Also almost all Walters examples are on large Continental or radial engines; they do NOT relate to a small 4-banger Lycoming's. An engine is an engine, but be careful before you assume too much, that's all. A big lumbering radial can blow a JUG clean off the plane and keep running pretty smoothly. Go up in a 4-banger lyc and shut the ignition off to one cylinder. If you have glasses and fillings in your mouth, you will loose them. The airplane will shake violently.

I am very conservative and tend to stay with established procedures that have been laid down for 50 years, but again I GET LOP. That is not my point. KNOW WHAT you are getting into, you better, because operations on the edge has draw backs. Draw backs are much higher pilot attention, knowledge and more instrumentation. Any one can be trained to do it, but you know some pilots are lucky to remember the cowl flap and lean at ALL. I know I was and am still a CFI with lots of dual given.

Cheers George

PS Important document: http://www.lycoming.textron.com/support/engineOperationTips/SSP700A.pdf.
 
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Other combustion studies carried out by Tim White, University of New South Wales in 1999 found that mixtures around 5% rich of stoichiometric caused the highest incidence of knock and that leaner mixtures than stoich (peak EGT) lessened knock. Detonation is highly unlikely at power settings corresponding to 75% or less unless ridiculous amounts of ignition advance are used.

While I agree that detonation CAN cause less serious damage than pre-ignition, this depends entirely on the magnitude of detonation present. Certainly many engines have operated for hundreds of hours in light detonation with little or no ill effects. Severe detonation where PCP exceeds 2500 psi will break rings and ring lands within a few seconds irregardless of the quality of the components. Detonation brings a reduction in power and is an abnomal state of engine operation. There is no good reason to operate the engine here.

Both detonation and pre-ignition are to be avoided if engine life is an important consideration and both can exist simultaneously. One can instigate the other under certain conditions. Pre-ignition will damage or destroy most engines in only a few seconds when operating at high rpm/ high power settings and is potentially more destructive than detonation.

As a builder of turbocharged racing engines for over 25 years, I have seen many instances of the damage caused by both phenomena.
 
gmcjetpilot said:
I think we agree, really; my poor wording may have messed you up.
Click to expand...
Yes, I do think the confusion was in the wording. If I should interpret you as meaning "Detonation may be caused by improper leaning" then I can certainly agree.

I don't envision a "stop" at peak EGT, so when you say "too lean" I assume you are at the point where the engine is about to quit, not peak EGT. Hence the confusion.
 
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I am willing to believe that "light" detonation for a limited time is not harmful. My high mileage Chev PU V8 pings going up hills if I burn cheap gas, to which I have reverted because of high prices. I can control the detonation to "light" levels because I can hear it and back off the throttle, downshift, or both. But you can't hear detonation in an airplane - too much noise - so how would you know? We need detonation detectors such as are found on cars. I understand that our air-cooled engines with their generous clearances between moving parts make too much of a racket for these sonic detectors to work. On the window sill in my shop is a piston from a P&W 1830 (DC-3) that suffered detonation and/or preignition. It looks just like the piston pictured in George's post, with melted ring lands and smeared skirts. It wasn't my doing but I understand it was caused by high power settings, low (climb) airspeed, and auto lean when they should have been running auto rich. This engine flew home but the same level of damage to a 4 cyl. Lyc would probably make it quit running. Something to think about when twiddling the red knob. Comments? Steve
 
GAMI Man

This thread was put forth as a general discussion of detonation/pre-igntion, but now I see the agenda is promotion of LOP operations. Dumb me :rolleyes:

Cheers George

PS Important document: http://www.lycoming.textron.com/support/engineOperationTips/SSP700A.pdf.[/QUOTE]

George,
I think you hit the nail right on the head. Advocacy of LOP is what all these threads are about. That becomes pretty obvious when GAMI sends one of their guys over to post on our forum.

You know what though, they are only claiming .9 gph to 1.5 gph savings from their injectors utilizing LOP. That's not unreasonable, and a far cry from some of the claims heard here on the forum.

Your right, though, one of the mod guys with 40 degree advance and 10 to 1 pistons is going to blow a piston clear into next Wednesday, and wonder why it happened. Good thing these engine monitors are download capable,
so we can all see why it happened.

John
 
Set the record straight

Go back and look at Walter's original post. The words "lean of peak" were not used once. Then take a look at Georges's response. I don't see the basis for asserting that GAMI sent someone over to advocate their product. I was looking forward to the dialog that could be provided in this forum by real experts but I'm sure they, and others like them, will opt out.

I'm done with this business.

Duane Zavadil
N678BT
RV6A
 
Good Technical Information.

I have to support Duane.
Unfortunately posts on this site are frequently opinion or anecdote served up as Technical Information. As technical fact.
Walter has provided what is easily recognised as GOOD TECHNICAL information.

I no longer bother to replies to posts with technical information such as , ?"A dangerously lean air/fuel mixture?. Dangerously? Any document containing such emotive language should be treated as suspect. And TOO LEAN OF A MIXTURE! Technical documents should clear and unambiguous. Too lean?? From what datum??? A richer mixture??

So here we had a good bit of technical input with none of the usual provocative issues,??? but they still get dragged in.

Walter, I wish to thank you for clarifying the detonation/pre-ignition events for me.
To suggest you had an ulterior motive in your post is reprehensible.
Reading some of the insulting responses to your brief, unfortunately leads me to doubt you will bother enlightening us again.

Oh, the Luddites?

Regards,
Pete.
 
BING-GO ding ding ding, or I mean ping ping ping

:rolleyes:
Stephen Lindberg said:
I am willing to believe that "light" detonation for a limited time is not harmful. My high mileage Chev PU V8 pings going up hills if I burn cheap gas, to which I have reverted because of high prices. Comments? Steve
Click to expand...
Steve my man, BING GO. First the looseness of the definition is of concern. If your Lyc is at 45% power, you can't hurt it. However above 65%, may be, 75% heck yes, 100% for sure. As you say what if you get BAD FUEL? Where is your margin.

How about after you do all that fancy leaning, you forget to enrichen and shove the throttle forward! OUCH!

Also as Yukon stated you have to define the engine. How do you really know you are detonating! YOU DON'T! At Lycoming they have test cells with very sensitive instruments to determine detonation. (I know, I asked them). In a car engine with water jackets and quite exhaust you can hear the detonation kicking your engines guts. Is it a nice sound? We need some "margin" unless you have the wherewithal to do testing. What works on a Bonanza's Continental may not work in a RV.

If some one says, oh I know when it is detonating by the EGT going down and CHT going up, I say how do you really know? How much DOWN UP are we talking about? You can pull the throttle back, go into a climb and decrease EGT and rise CHT! RIGHT? Detonation is insidious.

Steve, also I am a gear head from way back in high school and built many a small block Chevy. There is a big difference in detonation of a water cooled engine with a piston 1/2 the diameter. Just the word DETONATION makes you think, hummmm, that is bad. May be they should call it "murder death kill ". :D

Light detonation is like a little pregnant. Any detonation is damage, a little at a time. Even Walter admits it can damage plug ceramics, which in turn causes a hot spot and thus pre-ignition. There is nothing good about it.

When Walter says he went 5 hours detonating "an engine", it means nothing to an engineer. There is a BIG hole in the info. At 45% power, sure you'll do no harm. In fact you can't detonate. How do they know they where detonating? It takes sensitive instruments. There is just too much noise with an air cooled aircraft engine to hear the "PING" by ear or regular piezo transducer, but its there, knock-knock-rattle-ping-ping. Each time a hammer is slamming the piston and the connecting rod. It may not kill the engine all at once but can if the power (pressures) are high.

You don't know you are detonating with an aircraft engine, and those who swear they know for sure by an engine monitor are not being realistic. Are you going to stare at it. Do you have the patients to watch it. Who is looking for traffic? If you are below 65% power and have a parallel valve Lyc you will likely do no harm. Also remember in he old days the big engines that ran LOP had flight engineers that did that as a full time job. As a pilot do you have the time? May be.

LOP is not an across the board panacea. The trick is to get to 55% power not 75% power. If you want to save fuel throttle back. At 75%-100ROP, 65%-50ROP and at 55%-Peak, as base line targets, plus/minus. Any engine and pilot can do this and have margin with good economy.

LOP cost power and speed. Throttling back will also be slower, but it saves fuel also. To be honest I am not aware of any one who has flown a plane lean of peak, than flown at lower power with the same FF but ROP, measuring the speed difference. That would be a good data point.

Just want people to be safe George :D

Again read this document: http://www.lycoming.textron.com/support/engineOperationTips/SSP700A.pdf. As Clint Eastwood might say, A man's got to know his engines limitations.
 
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Facts nothing but facts

fodrv7 said:
Walter has provided what is easily recognised as GOOD TECHNICAL information.

I no longer bother to replies to posts with technical information such as , ?"A dangerously lean air/fuel mixture?. Dangerously? Any document containing such emotive language should be treated as suspect. And TOO LEAN OF A MIXTURE! Technical documents should clear and unambiguous. Too lean?? From what datum??? A richer mixture??
Pete.
Click to expand...
Pete if that's true, than you would hold Walter to the same standard. So ask Walter to give you some facts?

Reading Walters, first there are a 1000 pilots flying LOP? Than its two RV's, but he does not know the secret "CARB TEMP" (other thread on LOP with Carb engines). Than the 5 hours light / medium / heavy detonation engine test run? That means nothing to an engineer. Where are the facts, data numbers.

I submitted a Lycoming document and a Sky Ranch link to provide the data. I do have an engineering degree and have talked to Lycoming engineering about this, and the engineer I talked to attended one of Walters seminars. He said it was a good show. LOP, can be done. However comments like detonation is not a big deal, providing no details (facts as you say) is "dangerous". Aggressive leaning in climb at high power is another popular procedure de jour Avweb suggest.

According to Walter anything goes at any power setting? Well no, he did not say that exactly, but he just does not say. TRUST ME, you can kill your engine dead by leaning too much at high power. IT HAS BEEN DONE. Walter works for GAMI and they sell fuel injectors, and the sales pitch is LOP operations are good and GAMI injectors help. You decide but we need both sides of the story.

Cheers George
 
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Nobody Knows

Joey,

That's exactly the point. Nobody knows EXACTLY when detonotion will occur.
Nobody knows if your egt probes are EXACTLY in the right place, or if it's properly calibrated. Nobody knows when a cracked electrode or helicoil tang will prompt preignition/detonation. Nobody knows when you will forget to enrichen for the descent, and are too lean in the pattern on a go-around.

Conservative procedures cover all the "nobody knows". That's why Lycoming
makes conhservative policy for the masses. Because they have to show up it court to explain why their engine self-destructed. It's not always their fault.

John
 
Real Experts

zav6a said:
Go back and look at Walter's original post. The words "lean of peak" were not used once. Then take a look at Georges's response. I don't see the basis for asserting that GAMI sent someone over to advocate their product. I was looking forward to the dialog that could be provided in this forum by real experts but I'm sure they, and others like them, will opt out.

I'm done with this business.

Duane Zavadil
N678BT
RV6A
Click to expand...

Call me a skeptic, but I think you have heard the end of the free expert advise. For $395.00 I'll bet you call hear all you want. Here's the link:

http://www.advancedpilot.com/store.html

John - Just finished installing my Truetrak pitch servo
 
Yukon said:
That's exactly the point. Nobody knows EXACTLY when detonotion will occur.
Nobody knows if your egt probes are EXACTLY in the right place, or if it's properly calibrated. Nobody knows when a cracked electrode or helicoil tang will prompt preignition/detonation.
Click to expand...
That's a very good point. Given these shortcomings, I think we can both agree that it's important to give ourselves a healthy margin of error when it comes to detonation.

What range of mixtures gives us a healthy margin of error when it comes to detonation, John?
 
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Your good judgement

Joey,
That's up to the good judgement of every pilot. How much crosswind is too much for landing? How much fuel remaining do you feel comfortable with on arrival?

John
 
It isn't black magic

George,
Thanks for your response.
I think you make some good points.
I do respect your approach to offer of a word of caution to those contemplating LOP ops.

A LITTLE BIT OF KNOWLEDGE IS A DANGEROUS THING!

But all I saw in Walters post was raw information about Detonation and Pre-ignition. No comment on what to do with it. Definitely not LOP or buy GAMIs.

George, you and I have similar experience having been through the GA mill and onto heavy metal and we are cautious through experience. I don't mean experience as in, "We are smarter" but rather we have had the exposure and seen how you can be bitten by the unexpected.

For that reason, I am very cautious about LOP and have decided to take a very conservative approach until I know more. I only use LOP when I need the range, as I did yesterday during 5hrs 20min non-stop from Brisbane to Melbourne and then ONLY at 65% or less.

And that is why I appreciate Walter?s recent input. I want to know more.

But John, I don't accept that nobody knows. The whole Carnot Cycle http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/carnot.html was qualified and quantified 100 years ago by mathematicians and physicists. Today, the technology exists to measure every conceivable pressure, temperature, flame front velocity, fuel/air ratio and any other significant event within an engine, on a test bed. If anyone is doing that and willing to share the information then bring it on. The RED BOX is real and NOW defined, albeit, as you say, who knows if your plugs are damaged.

But I do agree with you that the conservative approach brings LESS risks. And ROP may provide that. But more knowledge will bring even less risk to ROP as well. Maybe Walter and John Deakin are flogging (Australian for peddling) GAMI injectors, I don?t know and don?t need to and don?t think it is relevant.
Why?
Because Walter & Deakin (of APS) publish data (free) that is clearly not selling LOP. They have a diagram of the Detonation zone which, besides showing where to operate LOP, shows you where to operate ROP.

So let's encourage research into piston engine combustion events. And if the people doing the research are financing the research by marketing a product, whether it be hardware (which I don?t think it is) of information in the form of Pilots Seminars, then let?s encourage them. Unless you can get Congress to fund it.

Cheers,
Pete.
Now. Excuse me. I'm going flying.
 
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A.p.s.

Yukon said:
Call me a skeptic, but I think you have heard the end of the free expert advise. For $395.00 I'll bet you call hear all you want. Here's the link:

http://www.advancedpilot.com/store.html
Click to expand...
Sounds like a great deal, and based on what I've read the class is outstanding. One day when I get the time I'll be there. I didn't actually expect APS to come here and dump their entire course here on these forum, and hang around for several weeks sharing all their research and experience for free.
 
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Here is a photo of a P&W 1830 piston that suffered detonation/preignition. There is damage to the rings lands all around the circumference; this is the worst spot. The top of the piston is marked by pieces of rings flying about. The underside of the piston dome is heavily coked from what I assume were very high piston temperatures. I cleaned this up with a bead blaster. I picked this up in 1993 while getting typed in the DC-3. As I recall, a mechanic told me it was due to a prolonged climb while in auto lean. I don't think the engine ran badly, only that it wouldn't make a power check pre-takeoff. Any insights/comments? http://img204.imageshack.us/img204/8711/img15220uc.jpg
 
Detonation

I have a piston just like that, but maybe a little worse. It came out of my Long-EZE when it detonated on auto gas. Pretty much ruined the whole engine.

John
 
Just Thanks

I just want to make a gratuitous post, I really like you guys. It is a pleasure chatting with intelligent gentleman. I am amazed at the depth of experience and knowledge on the list. Oh by the way can you spot me a $20. :D

Thanks for the input, Cheers George
 
George and John:

You two seem confused. For your clarification:

1) I do not nor have I ever worked for GAMI or TAT turbo in Ada, OK.

2) The light, medium and heavy detonation I referred to in the original post was in accordance with the FAA and engineering definitions of same. They were measured on the most advanced, computerized engine test facility in the world. The measuremetns were extremely accurate at sample rates of 50,000 samples per second.

3) As a result of these studies, the true understanding of these phenonmena are changing.

No one sent me here. You guys may feel quite comfortbale in ignoring my posts as others seem interested.

Thank you.

Walter
 
Yukon said:
Give us some credit, Walter.
John
Click to expand...
The above comment is snide and has offensive innuendo. And I am greatly concerned that it might completely drive away the one person who has brought any real science to the table in the course of this thread.
 
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What's your point?

Yukon said:
Give us some credit, Walter.
John
Click to expand...
Hi John, I'm not sure I understand your point here. Walter is coming over and providing us the benefit of his knowledge and experience, and is not asking anything in return.

He is affiliated with a company that is focused on researching aircraft engines in the exact environment we are discussing.

It seems like his group are the leading experts on this subject on the planet. They are teaching things that will help us operate these engines better.

If people read Walter's messages, and agree with my assessment that his knowledge is valuable, then they may want to learn more by attending one of his seminars. Great! If people don't want to go to his seminar, they were able to get some free information that can help them. Also great!

If you don't agree with the ideas being put forth please feel free to discuss the ideas, but please, let's leave the ad hominem attacks for talk radio.
 
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John:

**To what do we owe this honor?**

That's a very reasonable question.

1) I was asked by one of your members to join this forum in an effort to clarify some of the engine management misinformation that he perceived is spread here.

2) In one short, 24 hours I have discovered that he was right, there is a little disinformation closely held here that is not supported by any data.

and, more importantly,

3) in that short time, the [snip] have identified themselves.

Walter Atkinson
Advanced Pilot Seminars
 
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Thanks Walter

I for one appreciate your willingness to spread a little science here. I'm a scientist by temperment, if not by profession. I also appreciate opinion on this board, since many of the decisions I'm making don't have a scientific answer (tip-up vs. slider, etc.). Sometimes, however, it takes a little while to seperate the opinion from the science. And bullying seems to be an unfortunate consequence of these types of forums.
 
Don:

Thank you. Noted.

Let me comment on one thing that I noticed earlier in this thread. Someone suggested that John Deakin got a free set of GAMIjectors and wrote an article about them, implying a dishonesty to the report. Nothing could be farther from the truth. John bought the very FIRST set of GAMIjectors, serial number 1--and paid, full retail. He refused even a discount. He then paid FULL retail for his turbo installation--no discount. He is a gentleman of impectable honesty and will not be swayed from writing exactly what he thinks of any product based ont he science.

He and I both have been offered numerous products for free to evaluate and report on. Neither of us has ever accepted ANY product for free or even at a discount. We pay full retail and then we are free to report on the product as we see it. We can only maintain our objectivity and reputation for honest evaluation through that approach.

Also, as for the "Experts are Everywhere" document by Lycoming. It was written as a direct answer to George Braly. He is the target of that document. One day, Lycoming is going to be very embarrassed by that document as in part, its comments do not even agree with Lycoming's own data. Basically, if one reads it with a critical eye, it says that LOP ops are OK and that they work fine----but that pilots are too stupid to do it right.

I disagree that the pilots are too stupid. Others may disagree with me.

Walter
 
From Downunder

John,
I realise making a dollar is the perceived modus operandi of USA business, but you ought to make an effort to give consideration to the possibility that the odd businessman in the USA may have a touch of altruistic streak.

We in Australia do not make the claim of being a Christian Country as you are wont to do, but I have read enough to know, ?Let he who is without sin cast the first stone?, ??.to give and not ask for any reward? and ?It is more blessed to give than to receive? (Shakespeare actually.)

Maybe you might just offer Walter the benefit of the doubt here.

Pete.
 
Advertising

fodrv7 said:
John,
I realise making a dollar is the perceived modus operandi of USA business, but you ought to make an effort to give consideration to the possibility that the odd businessman in the USA may have a touch of altruistic streak.

We in Australia do not make the claim of being a Christian Country as you are wont to do, but I have read enough to know, ?Let he who is without sin cast the first stone?, ??.to give and not ask for any reward? and ?It is more blessed to give than to receive? (Shakespeare actually.)

Maybe you might just offer Walter the benefit of the doubt here.

Pete.
Click to expand...

Peter,

Here in America, when a business wants to advertise it's product, they buy a display ad and interested parties call for information.

Imagine what this forum would look like if Lightspeed posted two page forum messages telling of how undesirable mags are? Or Electronics International lectured about the evils of a direct reading oil pressure guage? What if Eggenfellner came on the forum and dumped on Lycosauruses, day after day?
What kind of forum would we have?

John
 
Hi, John. I'm new here, so cut me a little slack if I'm not up to speed on the culture of this forum. I have been participating in online aviation forums (fora?) for about 20 years, and every forum has a culture.

Here's Walter, who is a partner in a business that sells education. They teach engine management, do deep research, and charge people to come to the class.

So, he is here, giving away his product.

I guess it could be argued that in doing so, he hopes that someone will sign up for the class, but it seems to me that, in general, his time and his knowledge are being given, which would be a benefit to the pilots here.

I don't see how the "advertisement" slam/slur you offer is justified.

(DISCLAIMER: I have attended the Advanced Pilot Seminars class. I learned much, and it was also fun. I have no financial nor business arrangement with APS. I'm just a satisfied customer and a fan.)

Tom Gresham
 
Yukon said:
What kind of forum would we have?
Click to expand...

Many respected members of VAF that post regularly own businesses that cater to the aviation industry (Mahlon, Stein, Jay Pratt and even Doug come to mind). They regularly 'give away' their time to answer questions. Many people feel they provide usefull information. I'm sure many have purchased services from these guys based on getting 'to know' them here. Maybe thier motives are not altruistic may they are. Who cares? Unhappy customers have a way with getting the information back out (BMA everything, early dynon problems, late PMags, cracked backing plates on Whirlwind, broken cranks, cracked ryton sumps, crummy Vans fiberglass on and on)

I would be VERY interested in hearing input to those who *have* been to Walter's classes who disagree with him. After seeing the data believe what they teach is unsafe or have managed engines according to what they teach and found different or unsafe results. If 1000's (even 100's) of people have been to the classes and their methods are unsafe or bs certainly there must be an extrovert in the bunch that would call them on it and post here.

Most of us are grownups and can judge informaiton and motives without (repeated) help.
 
Chuck:

We have been offering a reward of $1000 to anyone who can provide any data-backed information which is at odds with our statements about the beneifits of our operating techniques. Why would we do that? Well, WE want to know where we are wrong more than anyone else.

So far, in seven years, no data has been offered. So far no one has taken issue with ANYTHING we have proposed with any repeatable, observable scientific data to the contrary--including Lycoming.

I've seen two [edited by dr for civility: members who disagree] show up in this thread. Neither has offered any data to support their opinions. If they have any, I would like to see it more than anyone else.

This thread was started to discuss one topic--detonation and pre-ignition. Let's get back to that. Let's leave personalities and supposed hidden agendas out of the discussion. Science only. My next post will do so.

Walter
 
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Good point Chuck

chuck said:
Many respected members of VAF that post regularly own businesses that cater to the aviation industry (Mahlon, Stein, Jay Pratt and even Doug come to mind). They regularly 'give away' their time to answer questions. Many people feel they provide usefull information. I'm sure many have purchased services from these guys based on getting 'to know' them here. Maybe thier motives are not altruistic may they are. Who cares? Unhappy customers have a way with getting the information back out (BMA everything, early dynon problems, late PMags, cracked backing plates on Whirlwind, broken cranks, cracked ryton sumps, crummy Vans fiberglass on and on)

I would be VERY interested in hearing input to those who *have* been to Walter's classes who disagree with him. After seeing the data believe what they teach is unsafe or have managed engines according to what they teach and found different or unsafe results. If 1000's (even 100's) of people have been to the classes and their methods are unsafe or bs certainly there must be an extrovert in the bunch that would call them on it and post here.

Most of us are grownups and can judge informaiton and motives without (repeated) help.
Click to expand...


Chuck,

You left out ECI rods and cylinders from your list!

And you make a good point. I don't hear Mahlon impuning Lycoming's judgement like Walter and Deakins do with regularity. Jay Pratt doesn't call out other assistance centers, and Doug is neutral on all topics.

Walter does a serious disservice to the sport when he criticizes Lycoming the way he does. GAMI will fall when they have to fight just one lawsuit of the magnitude Lycoming faces every day. This is a litigious business, and there's more to consider than just saving 9/10's of a gallon per hour.

Now I have said all I have to say on this topic. Walter, bring on your opinions if you have any left to share. I'm going back to work on my instrument panel! Thanks Affordable, you're the best!

John
 
Please Read...(from Doug Reeves - Forum Owner)

Walter,

Thank you for your post and welcome to the forums! It was educational and very much appreciated by me.

About some of the replies:
They have taken a tone that I do not approve of and will not let stand. A few posters are now 'under my microscope' and could very easily be banned in the near (and I do mean near) future. The time for testing the waters on 'where the line is' is over. Please don't push me on this - and rest assured you will lose if you do.

Doug Reeves
VAF Forums Owner
 
I have a .jpeg file which is the mathematical calculation for the official detonation index. I could not get it to upload to the forum. If someone who knows how to do that on this forum and is willing to help, I will be happy to e-mail them the file so it can be posted.

Using the FAA definitions, the knock index for light medium and heavy detonation is as follows:
Light: 21 bars
Medium: 74 bars
Heavy: 244 bars

I use the terms light, medium and heavy detonation specifically according to the above FAA definitions. That way there is no question as to what I mean.

There has been one Lycoming engine tested which will routinely experience light detonation on every takeoff if the FF is set even slightly below the max. This is not harmful and it is really interesting that these engines seem to run quite clean. The light knock acts to scrub the combusiton chamber and is not severe enough (see above definitions) to cause damage.

We demonstrate this on a live-running Lycoming engine approximately every 60-90 days to a classroom full of pilots and mechanics. The FAA has come to the facilty and attended the APS class to be educated on the topic as this is the factility with more experience and knowledge in this area than any other.

Earlier, someone posted a picture of a piston with edge damage, suggesting that it was from detonation. Extensive reasearch in this area has led us to conclude that that type of damage is, in fact, not from detonation, but from pre-ignition. We have watched a lot of detonation that has ranged from light to heavy (and recorded it into the computer for analysis) and as long as it was not allowed to progress into pre-ignition, no damage to the engine has been noted. That's the observation in a controlled environment. We do realize that this is counter to much of the conventional wisdom on the subject but is tempered with the reality that the conventional wisdom did not have the advantage of detailed recorded analysis. It is amazing how much of what I *knew* to be true, simply isn't when you look at the data with an open mind.

(FYI: Spark plugs begin to be blown out of the cylinders at around 1200psi. We know this from empirical data collect as the ICP rises above that and the plugs are blown out of the cylinders and onto the ramp.)

Someone referenced Lycoming's recommendations. Let me say that as a regular practice, base on MEASURED data, some Lycoming engines (at the T.O. and climb Fuel Flows recommended by Lycoming) experience ICPs of above 1100 psi as a matter of routine. This means there is not much margin for error.

(cont'd)
 
(cont'd from above post)

Quoting written Lycoming recommendations from their engineers.
From Textron Lycoming, Key Reprints from the Lycoming Flyer

1) Page 37. A chart of four of the five Landmark graphs of EGT, CHT, Hp and BSFC is labled clearly that Best Economy is found at approximately 40dF LOP. (the range, based on power, is from about 100dF LOP to about Peak EGT.) Lycoming either does not have ICP data, or does not publish it. Bottom Line? Best Economy is defined by Lycoming's engineers as 40dF LOP. That's in harmony with all of the known data.

2) Page 38. "Once cruise power has been set, leaning to Best Economy should be standard procedure as damage to the engine will not occur from leaning at cruise power settings."
It continues that leaning to best economy, " saves dollars and aids in safe flight."

Sounds suspiciously like Lycoming's engineers understood things pretty well.
Best economy should be SOP and is desirable.
Best economy is found at a LOP mixture.
Best economy is safer.

I'm finding no confusion on the issue according to Lycoming's engineers or the data they publish.

This Lycoming publication goes on to explain that they recommend Peak EGT as best economy because it is near the start of best economy and "it is our only practical point of reference." That means that if their F:A ratios are not adequately balanced to allow for smooth operation LOP, that peak is OK and the best they can do!

Now, what does this have to do with detonation?
A) Lycoming recognizes the safety aspects of being LOP.
Why?
B) They KNOW, as we do, that you simply cannot make these engines detonate when LOP in the normal operating cruise power ranges. We have tried diligently to force them to detonate when LOP and we have been miserable failures in that attempt.

THE most detonation-prone mixture setting is 40dF ROP. This is why Lycoming properly admonishes leaning at high power settings. They properly do not want the mixture anywhere near 40dF ROP like many pilots might do if they leaned to a mixture not rich enough or not lean enough!

Lycoming's DATA and their engineering is solid. Their marketing and legal department's writings are not so scientifically oriented.

I realize that any time new information takes one out of their comfort zone of what they THINK is true, it can make one uneasy. If anyone has any DATA that can be examined which is counter to that I have observed and reported, I very much would like to see it.

Please keep comments ON TOPIC. Detonation and Pre-ignition.

Thank you,

Walter Atkinson
Advanced Pilot Seminars
 
Walter Atkinson said:
I have a .jpeg file which is the mathematical calculation for the official detonation index. I could not get it to upload to the forum. If someone who knows how to do that on this forum and is willing to help, I will be happy to e-mail them the file so it can be posted. (snip)
Click to expand...
Walter, here are instructions for inserting images:
http://www.vansairforce.net/articles/ImagesInForums/images.htm

B,
D
 
Doug:

Thank you. Since I visit eight forums daily to answer engine management questions, I really don't have the time to do that.

Thank you anyway.

Walter
 
I will be happy to do it

Walter Atkinson said:
Doug:

Thank you. Since I visit eight forums daily to answer engine management questions, I really don't have the time to do that.

Thank you anyway.

Walter
Click to expand...
Walter: send it to my email and I will post it.
h
 
Thanks!

WALTER

I would like to express my thanks for you taking the time to post your data and experiences on this forum. This kind of open information is what I think is best about the internet.

We have had a couple of people stop contributing because of the actions of a small minority. I hope you will not be deterred and will continue to visit and contribute.
 
Further literature

Walter, I find this whole engine management thing most fascinating and I would like to take the opportunity to ask a couple of questions.


1. Why does mixture at approx 40 degrees ROP produces the fastest flame front, the hottest CHTs, and the highest ICPs.... but not max HP.

2. Why is mixture at approx 80 degrees ROP the mixture that produces max HP.

3 Why does a chemically correct mixture (stoichiometric) coincide with maximum heat being lost through the exhaust (max EGT).

4. For those who are based overseas and have no chance to attend your seminars can you recommend any literature (especially on-line) that might be enlightening. I've read all the Pelican's Perch articles.
 
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Bob Barrow said:
Walter, I find this whole engine management thing most fascinating and I would like to take the opportunity [snip] to ask a couple of questions.
1. Why does mixture at approx 40 degrees ROP produces the fastest flame front, the hottest CHTs, and the highest ICPs.... but not max HP.
2. Why is mixture at approx 80 degrees ROP the mixture that produces max HP.
3 Why does a chemically correct mixture (stoichiometric) coincide with maximum heat being lost through the exhaust (max EGT).
4. For those who are based overseas and have no chance to attend your seminars can you recommend any literature (especially on-line) that might be enlightening. I've read all the Pelican's Perch articles.
Click to expand...
Bob,

#1 Great questions

#2 Walter has had to deal with know it alls on every website he visits. He does so with a style and Grace of which I am jealous. I do not expect he will cut and run.
 
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Underated

Milt,
You do your self an injustice.
You too have a style to be admired.
Pete.
 
Pre-ignition

"Earlier, someone posted a picture of a piston with edge damage, suggesting that it was from detonation. Extensive reasearch in this area has led us to conclude that that type of damage is, in fact, not from detonation, but from pre-ignition. We have watched a lot of detonation that has ranged from light to heavy (and recorded it into the computer for analysis) and as long as it was not allowed to progress into pre-ignition, no damage to the engine has been noted. That's the observation in a controlled environment. We do realize that this is counter to much of the conventional wisdom on the subject but is tempered with the reality that the conventional wisdom did not have the advantage of detailed recorded analysis. It is amazing how much of what I *knew* to be true, simply isn't when you look at the data with an open mind."

Walter,

Assuming pre-ignition is the cause of the piston damage in that photo, how does one benefit from that knowledge? If you just blow-torched a piston and rings due to aggressive leaning, how does semantics make it any different?

In your estimation, what caused that kind of damage? How can it be avoided?

John
 
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Bob:

**1. Why does mixture at approx 40 degrees ROP produces the fastest flame front, the hottest CHTs, and the highest ICPs.... but not max HP.**

Flame front speed is a function of primarily three factors. The temperature and pressure of the combustion gasses are two. This mixture is where the combination of those two factors is the highest. The last factor is the over abundance of either air or fuel. Being very rich or leaner than about peak, results in a slowing of the flame front as the molecules try to find one another to react.

**2. Why is mixture at approx 80 degrees ROP the mixture that produces max HP.**

Maximum Hp is realized when all of the fuel is used up and the crank-conrod geometry is at it's most efficient. While Stoichiometric mixtures are defined as the mixture where all of the fuel and all of the air is consumed, in reality it is not quite true. Some of the molecules of oxygen and fuel never find each other to react at the stoichiomtric mixture and as a result there is a slight inefficincy. At about 80dF ROP, there is just enough extra O2 that all of the fuel molecules find some O2 to react with. It is also not so rich that the flame front is slowed down or that there is a huge over abundance of non-reactive air.

**3 Why does a chemically correct mixture (stoichiometric) coincide with maximum heat being lost through the exhaust (max EGT).**

The EGT is NOT a measure of the heat being lost. Many think that this *lost heat* is giving up Hp. It is not. EGT is NOT a measure of the heat of combustion. The heat of combusiton is fairly steady across the mixture spectrum. EGT is a measure of the exansion of the gasses from TDC to the point at which the exhaust valve opens and releases that gasseous pressure. Remember, from high school chemistry, PV = nRT. As the volume is changed, the temperature is changed. This is why high CR engines have lower EGTs and low compression engines have higher EGTs. It is also why timing and the thetaPP alters the raw EGT values. It's all in the expansion that takes place as the piston moves down.

Peak EGT occurs where it does because there is no extra air taking up volume that is not used in combustion. Same for excess fuel.

**3. For those who are based overseas and have no chance to attend your seminars can you recommend any literature (especially on-line) that might be enlightening. I've read all the Pelican's Perch articles.**

We recommned the Pelican's Perch articles as a prep for the APS class. While we've had a fair number of folks from overseas come to the class, we recently put the course on the internet so fewer would have to travel. The online course content is the same as the live class. You can get more info on the Online Course at <http://www.advancedpilot.com>. The Online Course requires a high speed connection to see the videos, the engine runs and high-res pictures.

I hope my answers helped. If I was not clear, let me know.

Walter
 
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