No. Degradation of performance tells you, Not Champion. They suffer degradation, and pretend it does not happen. Amazingly it is a direct correlation with a known causation. The fact a competitor has latched onto it does not alter the facts.

They have head buried in the sand on this and some other more serious matters that will not be discussed openly here.

Once discovered, it is obvious. A bit like fairies in your garden, they do not exist. Until you discover they do. Then what?

I would not have believed it several years ago. But data is hard to argue with, especially when a bunch is collected by yourself. I have never found one engine yet that runs smoother with high resistance plugs. Not one.

Interesting comments like you can change any thing, Once again costing into view here as in why did you change that plug for its got plenty of meat on it left. Champion state that when the plug is half worn its U/S. Generally before this you don't have any problems with plugs. Now one thing you half all missed that when a mag fires it has multiple discharge, It is not one spark but several. Also you have positive spark and negative sparks, this means that it fires from and to the centre electrode and this gives different wear patens. 4 cly engines a plug will not change per cylinder. Meaning that #1 cly will be a positive spark and #2 will be a negative. Now a 6Cly each time the plug fires it will be different one fire pos and the next will be neg and this gives a more even wear on the plug.
Next thing is if you follow the manufacture advice and have you mags and plugs change and serviced you really don't have a problem.
As for gapping you can gap both types of plugs period.
Now depending on the operation of the aircraft what engine it is there are variables to everything . The worse plugs for fouling I've found is training aircraft.
As for anyone being able to say that they can feel an engine with high gaps I truly find this hard to believe what was the engine ? The only way I know anyone can do that was on the large radial engine s that had oscilloscopes and the really good flight engines could pick which plug it was on a 28 cly, before my time but can remember story's and reading about it as a an apprentice

I don't think that's correct for most standard ignitions on standard GA piston engines. One spark and that's it. I think I've even seen a video of it. Look at the trace at the link in one of my earlier posts. (Of course, there are usually two plugs, each of which usually sparks at nearly the same time.) Correct. That's why you need to 'rotate' plugs from a positive spark position to a negative spark position. True. It's also true that any manufacturer of any product occasionally has quality control problems and produces bad batches. Yes you can, but you'll likely break iridium fine wires if you do. Ain't no engineer going anywhere near my fine wires with any gapping tool ... That's probably because training aircraft spend a lot of their time in service at low powers and full rich, such as during taxiing. They should be aggressively leaned on the ground, but most instructors learn and pass on ignorance. Magneto check LOP at altitude will usually be the first indication of degradation, but if you're used to the feel of the specific engine and the usual indications on the engine monitor, you can feel and see it as well.

You can do it the other way around: Collect some plugs with magic resistors that measure high or open resistance on a standard low voltage multimeter. Find an engine that's performing well. Change the plugs with the one's you've collected (after cleaning and gapping). Go fly. (Not my engine, please).

Jabba will probably chip in with his experience.

mmmm cream puff.
Ever heard of the hi performance ignition systems used in the aftermarket car industry. Its called MSD do you know why its called that. It multiply spark discharge. Its used to simulate a magneto.
I would have you have a look at the LAME syllabus and do some reading. A magneto has a multiply spark.
Ok the second ignition system is totally independent of each other, and propagates a more compete burn and a more even burn across the piston head. Also a redundant system which is it primary use.
Next thing is also is the mixture in the burn the leaner the mixture the slower the burn, the richer the mixture the faster the burn.
Basic LAME training.
As for breaking a plug well you can break any thing if you wish but you can also not break any thing. It would seam you possibly no more than your LAME may be you should change your profession ?
There are no one answer for any problem the rules are not always universal for any aircraft.
Cheers

How much 'hands on' time do you have on GA piston engines, yr right?

cream puff you say
True. It's also true that any manufacturer of any product occasionally has quality control problems and produces bad batches


Sorry this is totally incorrect.
Aircraft servicing is a preventative engineering process. This means we repair replace etc before it breaks or fails. Hence a in this instance we change plugs a the manufacture's recommendation's and have the magneto serviced at the 500 hrly inspection period as per manufactures service period instuctions.


If there is a bad batch then this is taken up else where, ie SB, MSB. AD etc etc

Cream Puff
Excess of 34 years and your self ?

Me? I'm just a wheel-chair bound geek from Hicksville USA. Flying machines scare me and engines are dirty!

So how many of those "hi performance ignition systems used in the aftermarket car industry" have you seen fitted to GA piston engines during your 34 years of hands-on GA piston engine experience? In round figures.

Well Cream puff
In Australia we would call you a ******** take it which ever way you like. You didn't answer the question so how long have you been in aviation for a start.
As for fitting a MSD unit you really showing your disregard for your own intellicahnce. Like I said it what MSD stands for there was no intent to say it is fitted to aircraft. However there are some units that can now be fitted to home build aircraft which are similar. Although they still use one magneto.
The Porsche engine used in the mooney hover dint use magnetos from memory but had dual independent ignition systems. This was a complex engine management system, Rotax also have a similar system although not as complex.
So as for fitting a MSD no I have not fitted one to any aircraft. But if you can read what I said and what it stands for then do some rescrach into magnetos.
Also the most powerful internal combustion engines a 10000hp top fuel nitro or funny car engine or so use magnetos that are made by guess who MSD

No, that won't do at all, yr right.

It was you who cited "hi performance ignition systems used in the aftermarket car industry" as the basis for your assertion that magnetos fitted to GA piston engines deliver multiple sparks. You could be correct (I very much doubt it), but if you are it won't be on the basis of what aftermarket car ignitions happen to do. Do you have any actual data or credible reference to cast doubt on the veracity of the trace at figure 1.0 at the link in my post at #26?

And you clearly spend very little time, if any, behind a GA piston engine on which your life depends. If you did, you'd know that occasionally manufacturers' commercial interests influence their recommendations and willingness to 'own' problems. (In that regard they are lot like engineers: Problems with engines are always caused by pilot mismanagement and never by poor design, poor manufacture, poor fitment or ham-fisted maintenance. Just ask the manufacturers and the engineers... )

And if you'd spent any real time behind a GA piston engine on which your life depends, you'd also know how plug problems manifest themselves in the air. Most of the plugs I've ditched were ditched due to actual, in-air problems, and those plugs were within manufacturer's specification and tested OK on the bench on the ground.

I'm sure you have many, many years of experience yr right, just like Trent 972. It's just that it's been the same year, over and over again.

Cheers Trent
I not here to peace to anyone just transform my knowledge onto others.
Cheers again
Always happy to share

Cream Puff you are a dill.
As an engineer I cant go above or beyond what the manufacture says. So end story.
They say 1 and I go 2 then you have an accident then you sue me then what grounds do I have,
Industry behind a piston engine, well my dad has over 20000 hours is that enough for you, like I said before I wont place a pilot or anyone I wont fly in my self. Never had a problem with a commercial pilot.
Sorry I guess if you have so much time on your hand you do some research on aircraft ignition systems and then learn a bout "E" gap but I guess you already know about that.

I see your point now.

Because I'm a dill and my brother grows elderberries, that proves there's nothing wrong with some resistors in some spark plugs.

Gotcha! :ok:

Yep, I know nothing about E gaps. I don't own a Unison T150 "E" gap gauge, which isn't part of my T-100 Assembly and Timing Kit and I've never used it in accordance with L-1363. ;)

Cream Puff
Great so please for you. I guess champion etc put them in so that you have some thing to complain about and know other reason spend all that time and energy and money for no reason at all

http://i60.tinypic.com/2cy5heg.jpg

So anyway ...

The little slug on the left is the magic resistor under discussion. The thing in the middle is an old plug.

(And the shiny gadget to the right of the plug is not a Unison T150 "E" gap gauge, which isn't part of my T-100 Assembly and Timing Kit and I've never used it in accordance with L-1363.)

We'll done a pic of a plug with a broken resistor. Only time you see it if you drop and break that plug. Think you will find it's main use is radio surpesion. Not 100% sure on that though. Do remember reading about it some time back. Like I've said earlier if you change your plugs regular they really don't give much trouble.
It's all in the detail.
Btw cream puff I use to sent aircraft in the middle of aust and never had a problem this was we on top of our planes and pilots. Might won't to have a look what's in the middle of aust and see what support is there. See it cost an awful lot to send an engineer on a break down here. It would seam if you are having trouble it may be something else wrong with you machine
Cheers

Whatever experience you may have, you haven't learnt much about bog standard Champion plugs.

You don't have to drop and break one to get the resistor out. You just unscrew the grub screw that holds it in.

The resistor in the picture isn't 'broken' in the physical sense. That's exactly the size and shape they are when they leave the factory. However, the one in the picture has a problem you can't see.

Sorry yes you can unscrew it but like I said only time you see it if you drop a plug other wise you don't see it as you don't unscrew it !!!!

Guys, don't know a lot about exactly what makes what happen with the spark system in exacting scientific detail, although I try to educate myself as much as I can on what makes an engine tick over nicely and what to look for in engine data to try and keep ahead of issues.

However I would like to share from experience in looking after our small fleet doing 3,000 to 4,000 hours a year combined, mostly all LOP and how spark plug health seems to effect our operations.

I read an article (about 5 years ago) on maintaining a good spark it made good sence and straight away I told our engineers to switch all aircraft at their next 100 hrly to all tempest fine wire plugs and every 100 hrly there after every plug was to be resistance checked and to throw away anything over 5,000 oms resistance.

It was an expensive exercise to change all plugs and the engineers thought I had lost it however within 6 months a few things happened that stood out. The aircraft average time of line dropped, our mag issues went away and we could get even lower average fuel burns LOP.

So don't acactly know the science behind why the mags are running happier although I have my suspicions but the bottom line is we seem to have much happier, efficient engines.

Maybe someone can touch on how plug health is related to mag health. The expense of switching to all fine wire and chucking what appears to be perfectly good plugs has been offset by sweet running mags and no more premature mag overhauls.

I maybe wrong but that's just what my data shows.

Mick
well im not quite sure exactly what to say, but when you have a closed fleet and you can manage and use the information that you can get from trending your engines you can make changes and monitor your changes in a positive or a negative. So by changing your plugs what else did you do..
Trending your engine wether turbine or piston is such an important tool. You are able to develop a knowledge of your machine and make changes to your fleet accordingly, use properly you will have a much more reliability.
I will just say well done
cheers.

Yr right, in my early years as a farm boy and fixing engines and pulling them apart just to see what makes them tick and trying always to improve things from trial and error is what I was taught on the farm. I grew up with briggs and Stratton, Holden and land rover motors, the old Cooper stationary engine and lister diesel engines. As a kid I found a glass plug that was used mechanics in go cart racing so they could tune the engines by looking at the color of the spark. I spent hours in the farm workshop playing around with spark timings and mixtures and leads whilst watching what it did to spark color and HP and found in the mag driven big old stationary pump engines that if a good strong spark was present then you could have a mass of problems else were and they would still run smooth.

If I think of the spark as water and apply things learnt about trying to keep pumps and pipelines going and keep a good supply of water up to stock isn't it the basic same principle. Look after the pipeline the pump will keep running smooth. Introduce any type of restriction or hammer in the line your flow slows, the pump, it knocks and hammers and self destructs and the stock fight for water and loose condition.

It maybe a non scientific and basic look at a very complex issue but I feel by taking away the restriction and allowing the mag to provide the spark in a way it is designed and a good even flame in the cylinder provides a nice even burn translates to a nice even power flow even timing and a happy engine.

From my experience I feel spark is the most neglected but most important step on the path to happy engine. At the moment I am looking at the next step and trying to work out the importance plug leads play and how reliable they can be.

I am happy to be corrected and learn more, just my experience and cheque book tells me I have stumbled onto something that works for me out here in the bush. Maybe it might for anyone else who has had problems in the past with premature mag failures and rough running engines.

Mick

It’s pretty simple.

Most of the things that can go wrong with a plug will result in the corresponding magneto having to work harder to make the plug spark. If, for example, the secondary coil voltage has to build to (and these are hypothetical numbers) e.g. 25,000 volts rather than 20,000 volts before the plug sparks, the coil is working harder, the coil is therefore working hotter, and the coil will therefore fail sooner. (By the way, on most standard GA piston engines, the coil is built into the magnetos.)

If you take a bog standard massive electrode plug, the gap is slowly getting bigger and therefore the voltage in the secondary has to build a little more to jump the gap. If left long enough, you can feel it in the engine. That’s why you gap massive electrode plugs.

Swapping to fine wire plugs solves at least the gapping problem, at least for 1,000 hours. (And please: Do yourself a favour and instruct your engineers not to go anywhere the fine wire plugs with a gapping tool unless they check with you first. If you’ve purchased Tempest fine wires, Tempest would rather replace or repair them for you, than have them wrecked by attempted gapping. And no: I have no direct or indirect pecuniary or other interest in Tempest or any seller of Tempest plugs. And yes: Your engineers might have successfully gapped old-style ‘dual fine wire’ plugs in the past, but they ain’t the same as the new iridium and other fine wire plugs.)

The internal resistor issue that is the subject of the discussion (for those capable of intelligent discussion) is the potentially more insidious problem. What’s undeniably happening is that when you measure the resistance of the internal resistor of a certain brand spark plug, using an ordinary, low voltage multimeter, the value becomes higher and higher as the plug gets older.

Now, the manufacturer of that brand plug says that the design and composition of the internal resistor is such that a measurement with an ordinary multimeter is meaningless. The manufacturer says that its internal resistors only work when exposed to the high voltages present in standard ignition systems.

The real world experience is this: When that brand plugs with resistors that measure very high or open circuit on an ordinary multimeter are replaced, the engines to which the new plugs are fitted run better.

Now it may be mere correlation rather than causation, but it’s an amazing correlation: The known symptoms of bad plugs – poorer engine performance and ultimately magneto problems – seem to go away when the plugs with very high or open circuit resistors as measured on an ordinary multimeter are replaced with plugs that maintain a constant resistance below 5,000 Ohms as measured on the same multimeter.

Your first-hand, real-world experience seems to be consistent with everyone else’s! :ok:

Mick
As ive said before its called preventive maintenance. What you say is what we do very well in the bush here in aust. Your thoughts are correct. Trend trend and more trends. If you run the same aircraft it doesn't take long to make a plan. Trends don't just mean engines. It can be every component. If you have a fleet you can work out when they fail and make a plan around that. A failure dose not nessacilly mean before a component is due on an M/M schedule. If you build up your component record you can get extensions although a little harder these days.
Fine wire plugs generally used on lower cylinder's where oil and lead can cause a problems. A little of topic but I just change the plugs on my turbo falcon after 100000k nearly no wear. Champion place a resistor in there plugs for a reason. You will also get longer wear out of a fine wire as oppose to a massive electrode plug.
For the average GA aeroplane there really isn't much gain in either plug. However the more you fly obviously the greater the gain you can have. The thing I transfer to owners is fuel is the cheapest thing you can put into your aircraft.
One place I worked the 500hrly mag inspection was turned into an O/H this was due that the conditions that the aircraft was fly to get the reliability it was required to do.
At the end of the day it all comes down to costs and if you wont to do it.

yr right perhaps you could give us your opinion on lean of peak operations?

More on plugs
 

Mick,
I am not surprised you saw an improvement in performance with fine wire plugs over your old massive electrodes fine wire plugs (regardless of the brand) will produce a hotter spark than massive electrode plugs every time. this is because iridium has a higher melting point than the massive electrode material and so can support a hotter spark without excessive wear. In order to create the greater spark the plug employs a bigger air gap (more resistance hence greater voltage build up to ionize the gap). Also teh smaller electrode does not shield the fuel air mixture from the spark.

As for testing the resistance that's fine, you chose tempest plugs and they require resistance tests, I only have a problem with testing champions which CANNOT be tested in this manner.

Creamie:
I wish you would back your arguments up with some reality, on the one hand you argue that extra voltage due to plug gap wears out the magneto faster on the other you argue that fine wires are better for your engine than masssives. Well guess what: fine wires have a greater gap and a higher discharge voltage than massive electrode plugs.

NGK suggests that excess voltage can damage a coil by overheating but that in order to do this (at least with their coils) they would require an air agp greater than 1 inch which does not occur with plugs.

And when you post the spurious blog post of a man (granted a switched on guy) connecting a TAZER to a plug as proof of your theories perhaps you could include the paragraph where he contacts the plug manufacturer and they say they would consider resistance testing: With a max resistance of 80,000Ohms!!!!!

Yr Right:
There are two reasons for the resistor: To prevent radio interference and to reduce something called capacitance after-firing, a condition where back EMF builds up in the lead shielding and then re-discharges across the spark gap after the firing sequence. The resistor in the plug ensures the back EMF discharges to ground via the shielding (easier path).

C'mon progressive.

You know perfectly well that the difference in gap, standard massive to iridium fine wire, makes a tiny difference to the necessary flashover voltage, all other things being equal.

As to the rest, I will comment after I've had a rest!

Lean of peak yep. DONT
When you lean an engine you slow the speed of the of the fuel burn. This means as the exhaust valve is opening instead of the fuel being completely burnt it is now burn out past the valve. Yes im aware of the article but I've seen the results of over peak leaning as many engineers have. Makes money for us. Simple how much fuel do you have to save to replace a $2500 cylinder. Oh and plus the other 5 cylinder's that have to be changed. Even worse if you try it with a turbo engine, added boost can cause a detonation and complete engine failure. Case in point the PA 31-350 in SA while he had an engine failure on one engine he went to a high power setting and didn't increase the mixture as I recall. Now what that means although he didn't intentionally lean to an over peak the result was the same. He then lost the good engine resulting in the loose of the aircraft and all on-board. Yes there lots of other thing that compounded that accident but engine failure stopped the aircraft fly, Was extremely sad.
At the end of the day the exhaust seat and valve don't lie.


So I guess its the owners choice but at the service its the engineers.
This is my personal view and not to be taken as a recommendation. At the end of the day you have to go by what the aircraft flight manual says.


Look owners says this this that, engineer looks sees that that ,this. The machine doesn't lie. Things don't fix them self's.

As an LAME we looked at indifferently. We cost you money, we are seamed as a nesacarry evil. We not out to cost we not evil.
We do a job which at time can be extremely difficult. The industry is bleeding engineers a greater rate than you all can imagine. GA engineers arnt black box change or open cheque book ex military engines either. Most know there stuff and are there to help.
The difference between an Engineer and a surgeon is that a surgeon burry there mistakes and generally only take out one at a time oh and get paid a **** load more than I do

Yr right.

1. Please explain what happens to exhaust valve and seat temperature as you lean the engine, from rich to peak and beyond.

2. Is the exhaust valve and seat hottest at; A. 150ROP B. 75ROP C.35-50ROP D. 20LOP



Are you sure? Lean operations occur on the LEAN side of Peak EGT. Rich operations occur on the Rich side of Peak EGT.

What you have seen is the results of poor manufacture at the OEM, and at times accelerated by temperature and pressure by operating at a mixture either not rich enough, or not lean enough. But it is not from operating LOP. To say such a thing shows a lack of understanding of the science.

American Airlines had 400,000,000 hours of data in the 60's about why their engines were now lasting to a TBO of 3600 hours when compared to around 700-750 hours when run ROP as you might be suggesting. That is ROP but not rich enough, or lean enough.

The Whyalla engines were run in the climb not rich enough, they were never LEAN operations as chemically they are ROP mixtures. The flaws in those engines were a defect in the crank, accelerated by mag timing advanced causing higher ICP's and CHTs. The other one had been operating in detonation from not rich of peak enough operations. This one failed due to a preignition event.

Detonation. This is something I am heavily involved with, I have seen more aviation gasoline detonation testing than I guess anyone in Australia, so I feel qualified to comment here. Under what circumstances can detonation be invoke?

A:Full Rich-150dF ROP ?
B:40dF LOP - Peak EGT ?
C: 35-50dF ROP?

With a conforming Normally Aspirated engine, on conforming 100LL can detonation be induced?

With a conforming Turbocharged engine, on conforming 100LL can detonation be induced, and if so under what conditions?

If you are interested, the NACA (pre NASA) did studies on valve temperature at varying mixture and other parameters circa WWII and later n the 60's Lycoming did the same, and oddly enough got the same result. In more recent years with far more sophistication the same data was collected and plotted with Internal Cylinder Pressure. The results of this are found in this well known graph.

http://i849.photobucket.com/albums/a...psbfb07cbb.gif

If you are willing to learn some things new, from the 1940's I am happy to help.

All the best. :ok:

Gentlemen, Thanks for a fascinating thread. Ilove how you Aussies can call a spade- a spade without chucking your toys out the pram and storming off...pretty sure this would have died a death if posted in Engineers and Tech, (where it probably belongs)

Right, I'm NOT an aircraft mechanic. I eventually had my own village repair garage, had a Crypton engine-tuner with a 'scope and knew how to read the trace

I grew up with side-valves, copper plug-wires, 6v electrical systems.
Plugs were simply an insulator with an electrode wire down the middle, held into a steel body......you could clean and regap indefinitely, until the ground-electrode was no longer over the end of the centre-one, but pointing at the side.....or the centre was burned away and recessed unto the insulator.
OK it wasn't efficient, but neither was the carb, camshaft, porting etc.

This wasn't good for Champion, the brand-leader, who exhorted you to clean and regap every 3,ooo miles, replace every 6,000
They sold a machine to sandblast, pressurise and fire the plug, ,with an observation- window and a chart to compare plug condition.......
Plugs were 4 for a pound (five bob each) and the marketwas saturated andstatic ,by the early 60's.

The advent of cheap transistor radios caused a huge growth in sales, Also it caused a lot of concern with the "crackle" of interference which was not addressed by add-on supressors- plug-caps with a resistor, and an in-line one in the King-lead.
The plug-makers quickly latched onto this! build -in a supressor-resistor, the insulator will bake it and in 12K miles it'll be fxxed! punters will HAVE to buy replacements....on top of that, we can up the price, 'cos it's now a highly-technical Resistor- plug....A marketing-man's dream!
Add in supressor cables for HT and you've another money-spinner. rubber insulation had already given way to PVC on HT leads and so a lot of damp-starting problems vanished.

I consistently had more problems with Champion ,than other brands
Afriend, an ex-transport driver, claimed to have seen skips full of rejects out back of their (now gone) (wonder why:} ) Liverpool factory.

I can confirm Ohm meter readings well outside spec. I can confirm the service-life of Bosch and NGK and Nippon -Denso (now just Denso) and resistor stability were far superior to the Champion product, which I, and thousands of others, stopped using. I can also confirm the scope-trace told the story...Champion failed sooner!

The bean-counters and marketing-men are probably to blame, but I find it indefensible to sell such a mission-critical component where the emporical evidence points to an in-built service-life limitation.

Recently talked on the net to a european Aviator....after fitting a new high-efficiency starter, the engine would not start or run .....he methodically fault-traced (Electronics engineer) and replaced the "almost new" Champions...having found the huge variation in resistance as reported by others...initially, just the "dead" ones were replaced, to confirm they were, indeed, the problem. engine started fine, but an excessive mag-drop prompted changing the others.....like fitting a new engine.! Of course, this problem is unique to him, they have never come across it before! thick, patronising c:mad:s Don't they realise the internet will expose their bull in a flash?

@Progressive are you on a Champion retainer? seems like you , along with Yr right,are sticking your fingers in your ears and shouting "la la la" until the detractors run away.......Well, lads, the evidence is overwhelming When Champion have gone the way of Lodge and other fine brands killed by fools and asset strippers, we'll have no joy in saying "TOLD YOU SO"

Jaba
Radial engines cant be compared to Lyc or Cont engines. To say that its manufacting faults is way to simplistic for a start. Ive change more than enough cylinders to see that. Operators that don't overly lean with no problems and others that do and have problems. Heat is transferred from the valve stem to the guild and from the valve to the seat. You all seam to be worried about the temp its the fact that the gas flow is not fully combusted and is still burning as it passes the valve. Hence it burns the valve. Once the valve is breached it then cant seal and more gas passes and it gets worse.


You can have all the graphs in the world, im sorry but real life has shown me a totally different out come. Im happy to keep change them out if you all wont to keep doing it, your not hurting my wallet.


Now on the accident. The ASTB started pre ignition from the lead on the top of the piston, how ever Lcy said that this was not the case, As I recall the first engine had a crank failaure and the second engine was move to a higher power setting with out the mixture being placed into full rich. Now pre ignition how is that caused ?????? leaning out perhaps. See fuel is also cooling and specially for air cooled engines. To get to an O Peak you must go though the hottest part of the burn. Like I said real world shows what happens.
Jaba always happy to learn btw

Remember rich mixture fast burn , lean mixture slow burn.

Steve
1st I am not saying that champion plugs are better or worse than any other plugs. Please read what I've said. If you change your plugs service your mags you generally have no problems. I'm happy to install fine wire plugs, its the owner that generally don't wont to move due costs.
Cheers

Staying out of the p155ing contest, this is how I understand fine wires and the combustion process.

0 to 100 microseconds after 'spark' begins the primary field collapses due to no longer receiving voltage and the secondary field begins discharging. As it is discharging, it is ionizing the fluid in between the center and ground electrode of the spark plug (the air/fuel mix). As the ion fields grow out from the center and ground electrodes, they eventually meet, and an ion path is formed. Essentially this is a wire in the air made out of ionized air particles, like a mini lighting bolt.

This is the point where voltage spikes. It takes a lot of electrical pressure (aka voltage) to create the ion path, up to 40,000v depending on the ignition system design. THIS is where spark plug gap plays the biggest role. The longer the distance between the electrodes, the more voltage is needed to create the ion path (i.e from the coil)

Once the ion path is created, the voltage drops. Combustion still has not happened yet.

After the ion path is formed, it begins to transfer all of that energy stored in the secondary coil. THIS is where combustion begins. As the energy is transferred between the electrodes, some of the air/fuel mixture is ignited. The combustion event is VERY small at this point (the "little buddy flame"). At this point, there is not much energy, so any that is absorbed means there is that much less energy to multiply out into the rest of the cylinder. This effect is known as quenching.

This quenching action is where fine wire plugs plugs win. There is less material to cause quenching, therefore, more energy to get out into the cylinder. This gives a more even burn. With LOP and high EGR strategies, low quenching becomes VERY important.

This quenching effect is also the reason gap is important. The bigger the gap, the farther away the 'little buddy flame' is away from the electrodes, therefore less quenching occurs.

At the point the energy from the secondary coil is released into the surrounding fuel/air mix (this point is the 'holy grail' for a good plug, how efficiently that energy is transferred), combustion occurs in the fuel/air mix and the spark plug is now irrelevant (although it's effects are not).

New plugs should be gapped correctly already from the factory these days, but any uneven burn across cylinders will eventually result in the gaps increasing unevenly as well with resultant issues. Replace them if you can't regap them (i.e fine wire plugs..they are too delicate)

yr right,
With the very greatest of respect, absolute bollox.
Engineering wise, the individual cylinder don't know how they are arranged around the crankshaft.
I have been operating both radial and flat engines for about 50+ years, with the same results.Good results.
You have undoubtedly seen some lousy exhaust valves and seats, as I have, but you have absolutely no way of determining that running lean of peak caused the problem.
I am always fascinated by the idea that opiniated non-flying LAMEs or LAMEs with a pilot license but limited flying experience so often claim to know more about engine handling than a properly trained pilot, properly being the operative word.
I disagree with JABA on quite a few subjects, but on engine handling and running lean of peak, he is spot on. He understands, in this day and age, what was common knowledge 50+ years ago.
The only difference is that, with GAMIjectors and modern engine monitoring gear, it can now all be done with greater efficiency
Tootle pip!!

PS: With the first aircraft I owned,a Chipmunk, I could tell when the plugs needed attention, by the way the engine, when gliding with the throttle closed, rattled the canopy.

yr right, as you are no doubt very aware, there are only a small handful of aircraft engine re-builders here in Australia. Of this small handful, the number of outstanding organisations can be counted on one hand with fingers to spare.

I attended an APS course (see this thread) and was heartened to see that the manager of one of these outstanding establishments was a presenter and the manager of another was a participant. That is, almost 100% of the best aircraft engine builders in Australia were in attendance!

Thank you again for your input, it is great that an engineer takes time to read and post on this forum. If you want to know which engine re-builders were at the course, feel free to PM me.

Ok lets start here then.
Radial engines are different , every heard of crank angle for a start and the difference I was referring to is the manufacture of the cylinder and then you have cooling as well.
GAM injector work because of the differing crank angle and are matched to each cylinder accordingly.
Also how are you monitoring the different cylinder's with muti cht egt or single probes.?


Jaba I sad earlier that how much fuel do you have to save to replace one cylinder if you run LOP. By your own admission you said that poor quality from the OME. Sorry you cant have it both ways.
What im saying is what I see, broken engines. I guess it keeps me in a job.


Now, I have read and sorry don't have the information here with me. Plugs have different heat ranges. Also when the plug fires the plug itself is a mini combustion chamber. It ignites then travels into the plug before shooting out across the piston head creating a flame front. This is totally different to a turbine igniter plug which has a flat face, im guessing that this provides a better flame front and as such a better more complete burn with a fine wire plug as opposed to a massive electrode which is mostly shielded mmm not sure but perhaps food for thought.

yr right

Your changing cylinders is undeniable. Your correlation and causation are where the issues are.

I notice you avoided all the simplest of questions I asked. Please have a go at them. I am not here to to embarrass an anonymous person, but if I can help educate all the better.

As Leadsled has pointed out, the cylinder does not know how it is arranged, whats more the fuel does not know either, nor who made the cylinder. And why does brand C have several orders of magnitude more trouble than brand L, or P&W or......?

You are correct in saying the heat is transferred through the seat (65-75%) and through the stem (25-35%), and it is the incomplete contact through the face/seat that starts the burning of valves, not the exhaust gas going past. In fact you could be surprised at a little data here dating back to before WWII.

Gases going out the exhaust not fully combusting can be made happen at VERY lean mixtures, so lean the engine is hardly producing power. People with good balanced air/fuel ratio's some times see this as a "second peak" of EGT. This happens when they are well past peak, off the curves above and then EGT rises slightly (just off the graph) and the drops as no more combustion occurs. More commonly known as ICO.

Which temperature is hottest? 50dF ROP or 50dF LOP ? And which has the highest valve temperatures? You might find this helpful from NACA http://ntrs.nasa.gov/archive/nasa/ca...9930091891.pdf

Whyalla, I have the coronial reports where all the real data came to the surface. Two of my colleagues were at the centre of this very material and I can assure you this helps a lot because reading a coronial is a cure for insomnia. But let me summarise it for you.

1. The left engine failed with a crankshaft failure, a manufactured in defect, which may have gone many more hours was exposed due to very high loads imposed on it during the period from installation and up until a few weeks prior to failure. This was a result of magneto timing being advanced several degrees. This failure was likely to happen some time, however the excessive loads brought the failure on sooner and unfortunately the swiss cheese started to have holes lining up.

2. The right engine failed by way of a preignition event. Preignition events are catastophicly destructive if let go for more than a minute. These engines were routinely run in the climb with the mixture leaned to a setting that was not rich enough but they were still RICH mixtures. This engine had the power increased considerably to deal with the loss of the right engine and the failure sequence of preignition followed once the circumstances were created.

Please note that the detonation in the engines cruise climb life could vary from light to medium and the engine could survive this and they often do their whole lives, particularly light detonation (as scientifically defined). However periods of heavy detonation will start to damage things and the most likely victim is in fact the spark plug ceramic. Once this fails, you now have a source of ignition long before the magneto fired spark event should happen. And I mean long before. On a Chieftan with statically correct timing, the actual spark event goes of in a range of 13-16 degrees before TDC, and yes that is not where you set the magneto for static timing purposes.

Once the preignition is started, it will continue unless it is deliberately stopped or until the cylinder pressures eventually beat the piston into submission and it fails.We have lots of data files to show you this and the post failure evidence to go with it.

I will answer one of my questions above for you, as this is crucial to your understanding how these events happen.
The answer is C

I have a dyno-detonation test run with several fuels being tested on my laptop right now. The engine is 300HP standard compression (not low) and the detonation starts around 23GPH and is extinguished around 17-18 GPH. This detonation was all on the RICH side of peak EGT and thus by definition can only be a rich mixture. We can never get a typical LOP mixture to detonate when LOP.

You would be surprised at what we have to do to get even a min spec avgas to detonate. In includes, running CHT's up above 430dF (not as high as red line) run the oil temp up at 220df, get the IAT up to 150dF and use about 34-35"MP. This then gets you into the kind of territory the engine on MZK was in. I would dearly love to post the screen shots but it is highly confidential test data. Happy to let you see it on my laptop screen though.

Light detonation is not particularly harmful, medium can be stressful and reduces longevity, heavy is damaging to plug ceramics and other area's such as pistons.

Fuel cooling. Another of the worlds best OWT's. Fuel only ever adds heat. ONLY. One post on pprune is not able to pass on the full education of how extra fuel on the rich side of peak reduces CHT. It works EXACTLY the same way that having a LOP mixture does it by reducing fuel. You will have to believe me on face value here, but the rate of transfer of BTU's to the head are affected by ICP and that alone. ICP is a function of spark timing and thetaPP which affects the volume when the peak is reached. I could write for days and not convey this properly.

This is only half the story. Rich mixtures (by true definition) can burn faster or slower depending on where on the mixture scale they are. You are assuming that fast burns are a good thing and slow are bad. But you seem happy with the same slow burn with a richer mixture, which coincidently would have more fuel available to burn in the exhaust.

Take Aussie Bob's lead and book in for Perth. If you are not satisfied at the end that you did not learn a heap....money back :ok:

PS: Leadsled....thanks for the recognition. :ok:

Jaba
Ok let me say that what works on the computer is not always what happens in real life.
Simply put there are a lot of differences between manufactures, what material they made of comp ratios ignition timing etc etc etc. Detonation is always harmful period. Just because it didn't break now doesn't mean its not going to break. Stress now may not show now but will. The most harmful thing is that force is placed onto the big end bearing. This is the part that generally fails first.


As I recall the ATSB said it was pre ignition due to the lead and carbon on the piston head. Lyc rejected this totally. You said that was not overly lean well it must have been. full power full rich.
You said that fuel dosnt have a cooling affect. MMMM so how come when I pull the red knob back the egt cht rise, ?


At the end of the day I see the results. Ill just keep changing them out. Im Happy to do that.
Cheers always happy to learn

Jaba
Sorry so much going on I missed this,
You said the cylinder dose not know where it is. Well this is true it doesn't have a brain.
How ever there a a multitude of difference between each cly on an opposed engine, Crank angle for a start, cooling is different front to back, fuel require for the burn is different between them that's why you can use GAMI injectors. Is it injected or carby, if carby then you get a different flow between each cylinder.
Now ever wondered why P&W never made an opposed engine ? I have.
Areo engines are like no other internal combustion engine. Automotive engines don't work no matter how had they try I guess exception is a VW engine but that's not in commercial use.
Rotary's where to be the next best thing they couldn't make a gear box to take the hymonic load light enough.