Commercial Pilots who don't know about piston engines
So what is your theory on why piston engines work, oggers, and what is your theory on what happens to EGT, CHT and ICP as the fuel air ratio is varied across the spectrum that will support combustion?
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oggers
You have been asked nicely on the previous page some simple questions to help in the education process yet you seem more intent on some asinine game of what is a scientific fact and a hypothesis.
I think you have just proven a fact……….an unintended consequence no doubt.
If I am grossly off the mark maybe Lead ballon or someone else can set me straight but I seriously thing you are wasting everyones time.
Yes, and when this observation is repeatable and not some random result, it is….well…..it is what it is. Pretty much all the APS teachings are based on the "observations" of the likes of Pratt & Whitney, Curtis Wright, heck even Lycoming and TCM. Not to mention thousands of hours doing FAA certification testing etc at the Carl Goulet engine test facility.
So……have you a point?
You have been asked nicely on the previous page some simple questions to help in the education process yet you seem more intent on some asinine game of what is a scientific fact and a hypothesis.
I think you have just proven a fact……….an unintended consequence no doubt.
If I am grossly off the mark maybe Lead ballon or someone else can set me straight but I seriously thing you are wasting everyones time.
A "scientific fact" is an observation
So……have you a point?
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Jabawocky
NACA-754 Figure 8:
Figure 8b.png
Valve temp correlates very well with EGT. What glasses do you recommend to change that fact – beer goggles perhaps. Note the blue line I added where Walter Atkinson wrongly claims peak valve temp occurred is actually outside the range in which the report authors say it occurred.
I don't doubt that Lycoming have acquired plenty of data for their valves. But they did not draw the conclusion that you and Walter Atkinson have – quote: “EGT does NOT affect valve temperature...valve temperature does NOT track EGT...the two are not in any way related”.
Walter Atkinson:
You are clutching at straws. Eyeballing the curve from the test with the thermocouple gives a peak valve temp at no more than 10ROP, not your 25ROP and definitely not the 40°ROP you claimed previously.
But that is beside the point. The knowledge that valve temperature is linked to both CHT and EGT is well and truly established in the engineering literature and the publicly accessible data.
Easy: the spread between where CHT and EGT peak as a function of mixture means the valve temp will not peak precisely at either but between them. 
This extract is from a document by Electronics International that is very well referenced throughout:
“During the exhaust stroke the high velocity of the exhaust gasses and the large surface area of the exhaust valve head cause the exhaust valve to absorb a significant amount of heat. The temperature of the hot exhaust gasses (EGTs) flowing over the valve has a direct affect on the temperature of the exhaust valve. The exhaust valve is heated during two of the four strokes of the engine (power and exhaust strokes). During the exhaust stroke, the valve loses its major cooling path (valve seat face to the seat insert).” http://buy-ei.com/wp-content/uploads...ots-Manual.pdf
Meanwhile you have provided nothing to support the APS hypothesis that “EGT does not affect valve temperature...[and]...exhaust valve temperature is not related to EGT in any way”.
oggers, you are simply not correct....Time to put your glasses on, figure 8 clearly shows that statement is false.
Figure 8b.png
Valve temp correlates very well with EGT. What glasses do you recommend to change that fact – beer goggles perhaps. Note the blue line I added where Walter Atkinson wrongly claims peak valve temp occurred is actually outside the range in which the report authors say it occurred.
This same data was repeated in tests done by Lycoming in the 1960's.
Walter Atkinson:
According to the 1943 NACA report referenced, those who think that valve temp is in any way related to EGT must reconcile the fact that as EGT is going UP from 25dF ROP to peak EGT the valve temperature is going DOWN. This is definitive evidence that the two are NOT related.
But that is beside the point. The knowledge that valve temperature is linked to both CHT and EGT is well and truly established in the engineering literature and the publicly accessible data.
reconcile the fact that as EGT is going UP from 25dF ROP to peak EGT the valve temperature is going DOWN
This extract is from a document by Electronics International that is very well referenced throughout:
“During the exhaust stroke the high velocity of the exhaust gasses and the large surface area of the exhaust valve head cause the exhaust valve to absorb a significant amount of heat. The temperature of the hot exhaust gasses (EGTs) flowing over the valve has a direct affect on the temperature of the exhaust valve. The exhaust valve is heated during two of the four strokes of the engine (power and exhaust strokes). During the exhaust stroke, the valve loses its major cooling path (valve seat face to the seat insert).” http://buy-ei.com/wp-content/uploads...ots-Manual.pdf
Meanwhile you have provided nothing to support the APS hypothesis that “EGT does not affect valve temperature...[and]...exhaust valve temperature is not related to EGT in any way”.
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Sillo,
Couple of things here, the calorific values of fuels varies by tiny amounts, not worth the discussion point. The different octane ratings means you get to use the fuel with higher boost or higher compression ratio to achieve more power, while maintaining detonation margins that are acceptable. And acceptable varies from airplane to race car and everything in between.
As for if an EGT probe fails? Well no, once you are "known to be LOP" a probe failure matters not, because validation from all the others, your fuel low etc…..means the EGT probe is just validation of a know state.
You can comply with the POH supplement without even looking at the egt info if you want.
Couple of things here, the calorific values of fuels varies by tiny amounts, not worth the discussion point. The different octane ratings means you get to use the fuel with higher boost or higher compression ratio to achieve more power, while maintaining detonation margins that are acceptable. And acceptable varies from airplane to race car and everything in between.
As for if an EGT probe fails? Well no, once you are "known to be LOP" a probe failure matters not, because validation from all the others, your fuel low etc…..means the EGT probe is just validation of a know state.
You can comply with the POH supplement without even looking at the egt info if you want.
I can't see casa being happy with that, I know it is knit picking but this is where we end up with the regulator sometimes.
So now you are ROP for a few runs here and there and when the hundred comes up it turns out all is ok with the engine, great. However if at the hundred all is not well and you have a burnt valve or fried waste gate etc where do we point the finger LOP or ROP. Like all aircraft things break or go u/s and I am yet to see a machine that has some sort of magical wizard induced spell with such 100% reliability, isn't that why we have mel's.
So you have a MEL shouldn't this be on the MEL and if so what does it say , I'd like to see that page.
Eyeballing the curve from the test with the thermocouple gives a peak valve temp at no more than 10ROP, not your 25ROP and definitely not the 40°ROP you claimed previously.
What is your theory on why valve temperature goes DOWN as the mixture is further leaned past that point - whatever it is - and EGT continues to go UP to peak?
Even on your own observation and interpretation of NACA-754 Figure 8, valve temperature starts going DOWN before the EGT peaks. How can that be so, if EGT 'drives' valve temperature?
The knowledge that valve temperature is linked to both CHT and EGT is well and truly established in the engineering literature and the publicly accessible data.
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Ok fair enough if the probe fails and you are LOP at that time I agree you where compliant when it was set so that's fine, but what of the next flight ie returning to base let's say it's a two hour flight. Surely you can't comply then with a failed probe, your only option is to run ROP to be compliant. All this talk about that you must have good monitoring gear to go LOP which I agree with but when it fails it's still ok to go LOP?.
But trust me on the return flight, using known data, you set the same MP/RPM and Fuel flow, and the 5/6 that still work will confirm you were back exactly where you were before.
Stop trying to find ways not to do things……the glass is half full.
And seriously, if you want to call me and thrash it out properly, drop me a PM or send me your number. Happy to point you in the right direction.
And whats this burnt valve thing got to do with anything…..seriously, there are many old wives tales that you could benefit from killing.
Ok fair enough if the probe fails and you are LOP at that time I agree you where compliant when it was set so that's fine, but what of the next flight ie returning to base let's say it's a two hour flight. Surely you can't comply then with a failed probe, your only option is to run ROP to be compliant.
Think about what Jabba said. All your EGT probes are working. You set a mixture that results in all the cylinders being LOP. You have a known MP, RPM, density altitude, IAS fuel flow and CHT for each cylinder.
You then snip the connections to all the EGT probes. What changes in the engine? Nothing.
You then do a touch and go, and climb at full rich (not the most efficient way to get there, but let's not complicate things) and max RPM, and then level off at the same density altitude as before and set the same RPM and fuel flow as before. The MP is the same as before, and you note the IAS is the same as before and the CHT for each cylinder is the same as before.
It's very (very) probable that all the cylinders are at the same or nearly the same point LOP as they were before. And anything that would change that outcome would mean you couldn't be sure you were ROP and "compliant".
By the way, oggers, if you read the paragraph on the page after Figure 8 of NACA-754, it says:
[bolding added]
And before you leap at the phrase "reasons why lean-mixture operation is detrimental to valve life", note (with your calibrated eyeball) where the fuel-air ratio of around 0.065 - 0.070 is on the lean curve in the graph: rich of peak EGT.
When the report talks about "lean-mixture", it's not talking about lean of peak mixtures. It's merely talking about a mixture that is lean relative to another mixture that supports combustion. Every mixture that supports combustion is on the lean curve, somewhere. It's just that some are LOP, some are ROP and one is P.
So the report shows that the mixture ratio that imposes the most severe temperature on the exhaust valve is one that results in an EGT that is rich of peak. The report says the valves would probably give more satisfactory service if operated with a leaner mixture than one that results from a fuel air ratio of around 0.065 - 0.070.
The simple messages that APS tries to communicate are: if you're going to run ROP, run far far enough ROP; if you're going to run LOP, run far enough LOP; and the setting at which you're going to give your engine the hardest beating you can give it is ROP. Those messages are completely consistent with NAC-754 and all other relevant data.
The high valve temperatures accompanying operation with fuel-air ratios in the region of 0.065 is one reason why lean-mixture operation is detrimental to valve life. Injection carburetors are frequently adjusted to give a fuel-air ratio of 0.070 for cruising. From the foregoing discussion it is evident that this mixture ratio imposes the most severe temperature on the exhaust valve. The valves would probably give more satisfactory service if operated with a leaner mixture.
And before you leap at the phrase "reasons why lean-mixture operation is detrimental to valve life", note (with your calibrated eyeball) where the fuel-air ratio of around 0.065 - 0.070 is on the lean curve in the graph: rich of peak EGT.
When the report talks about "lean-mixture", it's not talking about lean of peak mixtures. It's merely talking about a mixture that is lean relative to another mixture that supports combustion. Every mixture that supports combustion is on the lean curve, somewhere. It's just that some are LOP, some are ROP and one is P.
So the report shows that the mixture ratio that imposes the most severe temperature on the exhaust valve is one that results in an EGT that is rich of peak. The report says the valves would probably give more satisfactory service if operated with a leaner mixture than one that results from a fuel air ratio of around 0.065 - 0.070.
The simple messages that APS tries to communicate are: if you're going to run ROP, run far far enough ROP; if you're going to run LOP, run far enough LOP; and the setting at which you're going to give your engine the hardest beating you can give it is ROP. Those messages are completely consistent with NAC-754 and all other relevant data.
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Lead Balloon
I gave the explanation in the very same post. But here it is again 
It is a no brainer. The observation that exhaust valve temp - as a function of mixture - begins to fall slightly rich of peak EGT does not in any way invalidate the theory that valve temperature correlates with some combination of CHT and EGT. In fact, as the working fluid is the heat source and the cylinder head is the heat sink, it cannot be otherwise.
What is your theory on why valve temperature goes DOWN as the mixture is further leaned past that point - whatever it is - and EGT continues to go UP to peak?
Easy: the spread between where CHT and EGT peak as a function of mixture means the valve temp will not peak precisely at either but between them.
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By the way, oggers, if you read the paragraph on the page after Figure 8 of NACA-754, it says:
Quote:
The high valve temperatures accompanying operation with fuel-air ratios in the region of 0.065 is one reason why lean-mixture operation is detrimental to valve life. Injection carburetors are frequently adjusted to give a fuel-air ratio of 0.070 for cruising. From the foregoing discussion it is evident that this mixture ratio imposes the most severe temperature on the exhaust valve. The valves would probably give more satisfactory service if operated with a leaner mixture.
[bolding added]
And before you leap at the phrase "reasons why lean-mixture operation is detrimental to valve life", note (with your calibrated eyeball) where the fuel-air ratio of around 0.065 - 0.070 is on the lean curve in the graph: rich of peak EGT.
When the report talks about "lean-mixture", it's not talking about lean of peak mixtures. It's merely talking about a mixture that is lean relative to another mixture that supports combustion. Every mixture that supports combustion is on the lean curve, somewhere. It's just that some are LOP, some are ROP and one is P.
So the report shows that the mixture ratio that imposes the most severe temperature on the exhaust valve is one that results in an EGT that is rich of peak. The report says the valves would probably give more satisfactory service if operated with a leaner mixture than one that results from a fuel air ratio of around 0.065 - 0.070.
Quote:
The high valve temperatures accompanying operation with fuel-air ratios in the region of 0.065 is one reason why lean-mixture operation is detrimental to valve life. Injection carburetors are frequently adjusted to give a fuel-air ratio of 0.070 for cruising. From the foregoing discussion it is evident that this mixture ratio imposes the most severe temperature on the exhaust valve. The valves would probably give more satisfactory service if operated with a leaner mixture.
[bolding added]
And before you leap at the phrase "reasons why lean-mixture operation is detrimental to valve life", note (with your calibrated eyeball) where the fuel-air ratio of around 0.065 - 0.070 is on the lean curve in the graph: rich of peak EGT.
When the report talks about "lean-mixture", it's not talking about lean of peak mixtures. It's merely talking about a mixture that is lean relative to another mixture that supports combustion. Every mixture that supports combustion is on the lean curve, somewhere. It's just that some are LOP, some are ROP and one is P.
So the report shows that the mixture ratio that imposes the most severe temperature on the exhaust valve is one that results in an EGT that is rich of peak. The report says the valves would probably give more satisfactory service if operated with a leaner mixture than one that results from a fuel air ratio of around 0.065 - 0.070.
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The simple messages that APS tries to communicate are: if you're going to run ROP, run far far enough ROP; if you're going to run LOP, run far enough LOP; and the setting at which you're going to give your engine the hardest beating you can give it is ROP. Those messages are completely consistent with NAC-754 and all other relevant data.
It is a no brainer. The observation that exhaust valve temp - as a function of mixture - begins to fall slightly rich of peak EGT does not in any way invalidate the theory that valve temperature correlates with some combination of CHT and EGT. In fact, as the working fluid is the heat source and the cylinder head is the heat sink, it cannot be otherwise.
What causes the CHT to go DOWN even though the EGT keeps going UP?
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How will you know the cylinder is running ROP if the EGT probe has failed?
Think about what Jabba said. All your EGT probes are working. You set a mixture that results in all the cylinders being LOP. You have a known MP, RPM, density altitude, IAS fuel flow and CHT for each cylinder.
You then snip the connections to all the EGT probes. What changes in the engine? Nothing.
You then do a touch and go, and climb at full rich (not the most efficient way to get there, but let's not complicate things) and max RPM, and then level off at the same density altitude as before and set the same RPM and fuel flow as before. The MP is the same as before, and you note the IAS is the same as before and the CHT for each cylinder is the same as before.
It's very (very) probable that all the cylinders are at the same or nearly the same point LOP as they were before. And anything that would change that outcome would mean you couldn't be sure you were ROP and "compliant".
Think about what Jabba said. All your EGT probes are working. You set a mixture that results in all the cylinders being LOP. You have a known MP, RPM, density altitude, IAS fuel flow and CHT for each cylinder.
You then snip the connections to all the EGT probes. What changes in the engine? Nothing.
You then do a touch and go, and climb at full rich (not the most efficient way to get there, but let's not complicate things) and max RPM, and then level off at the same density altitude as before and set the same RPM and fuel flow as before. The MP is the same as before, and you note the IAS is the same as before and the CHT for each cylinder is the same as before.
It's very (very) probable that all the cylinders are at the same or nearly the same point LOP as they were before. And anything that would change that outcome would mean you couldn't be sure you were ROP and "compliant".
I am just trying to get a picture of how we would advise casa we could comply in the case of a engine monitor or probe failure, and what goes in the Ops manual. Obviously we can't always cruise at the same level or power setting due maybe traffic or a crossing time requirement etc, understanding casa only has to accept your method not approve it.
So in that situation we would revert back to old school using the TIT probe and lean the engine to peak egt and then richen by 125 degrees at say 65% power.
Does a jpi monitor qualify for original aircraft certification?
Not sure, still I wouldn't remove the TIT probe hence its still there as backup.
I am just trying to get a picture of how we would advise casa we could comply in the case of a engine monitor or probe failure, and what goes in the Ops manual. Obviously we can't always cruise at the same level or power setting due maybe traffic or a crossing time requirement etc, understanding casa only has to accept your method not approve it.
I suppose you just have to pray that you find someone in CASA that isn't chock full of folklore. Lots of luck with that.
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The increase in CO2 as a percentage of the atmosphere correlates with the decrease in the the number of pirates (as any practising Pastafarian knows). But the decrease in the number of pirates has not caused the increase in CO2 as a percentage of the atmosphere (as any practising scientist knows).
What causes the CHT to go DOWN even though the EGT keeps going UP?
What causes the CHT to go DOWN even though the EGT keeps going UP?
Now, the APS hypothesis brought to us here by Walter Atkinson is "valve temperature does NOT track EGT...[the NACA report with thermocouple in the valve] is definitive evidence the two are not in any way way related" is not supported by that report or any other piece of literature I have seen. The part of that report you and Walter both cite as definitive is the valve temp peaking slightly rich of EGT. But it does not follow that valve temperature does not track EGT. The correlation with EGT alone is a very good proxy for valve temperature as a function of mixture. When you add the influence of CHT (as indicated in figure 8 of that report by the spark plug bushing) it becomes apparent why the valve temp peaked slightly rich of EGT.
Now to illustrate the absurdity of Walter's logic let us also test the APS teachings against it:
"EGT is NOT the indication you're looking for. Pay attention to the CHT, and the valves take care of themselves.com." John Deakin; Fried Valves
QED
Last edited by oggers; 7th Apr 2016 at 12:16. Reason: grammar
[Y]et it is the hottest component in the engine and highly stressed so it is useful to know how it correlates with CHT and EGT.
Now, the APS hypothesis brought to us here by Walter Atkinson is "valve temperature does NOT track EGT...[the NACA report with thermocouple in the valve] is definitive evidence the two are not in any way way related" is not supported by that report or any other piece of literature I have seen.
The part of that report you and Walter both cite as definitive is the valve temp peaking slightly rich of EGT.
But it does not follow that valve temperature does not track EGT.
However, valve temperature does not "track" EGT in fact.
The correlation with EGT alone is a very good proxy for valve temperature as a function of mixture.
Now to illustrate the absurdity of Walters logic let us test the APS teachings against it as well:
Quote:
"EGT is NOT the indication you're looking for. Pay attention to the CHT, and the valves take care of themselves.com." John Deakin; Fried Valves
Refer to figure 8 again. The CHT as represented by rear spark plug bushing. As a function of mixture it is going DOWN as the valve temp is still going UP. Now according to what you and Walter are saying this would be "definitive evidence" that CHT "does NOT track valve temperature and the two are in no way related". But of course, all it really means is that CHT - as a function of mixture - does not correlate with valve temperature as well on its own as it does when combined with EGT.
Quote:
"EGT is NOT the indication you're looking for. Pay attention to the CHT, and the valves take care of themselves.com." John Deakin; Fried Valves
Refer to figure 8 again. The CHT as represented by rear spark plug bushing. As a function of mixture it is going DOWN as the valve temp is still going UP. Now according to what you and Walter are saying this would be "definitive evidence" that CHT "does NOT track valve temperature and the two are in no way related". But of course, all it really means is that CHT - as a function of mixture - does not correlate with valve temperature as well on its own as it does when combined with EGT.
Got me a beauty, oggers! (You're not a Pastafarian, by the way?)
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Well, well, well. If one says a stupid thing fifty million times, it is still a stupid thing. paraphrased from Anatole France.
If one looks at the CHT and ICP curves and valve temp, one would see a nice correlation. The EGT is a red herring. The NACA report does not show all of the issues. These issues have been clarified quite nicely by Lycoming in 1966 and in the Carl Goulet Memorial Engine Test Facility. The physics are everywhere the same.
The EI explanation has been proven wrong by multiple sources. Several other of EI's statements have been such.
"There are none so blind as those who will not see." It gets to be a waste of time to try to educate those folks. I only continue to respond to these acts of rubbish for those who are lurking and wanting to learn.
Now, back to your regularly scheduled programming.
If one looks at the CHT and ICP curves and valve temp, one would see a nice correlation. The EGT is a red herring. The NACA report does not show all of the issues. These issues have been clarified quite nicely by Lycoming in 1966 and in the Carl Goulet Memorial Engine Test Facility. The physics are everywhere the same.
The EI explanation has been proven wrong by multiple sources. Several other of EI's statements have been such.
"There are none so blind as those who will not see." It gets to be a waste of time to try to educate those folks. I only continue to respond to these acts of rubbish for those who are lurking and wanting to learn.
Now, back to your regularly scheduled programming.
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Balloon
Hmm. As I have posted a couple of times already neither EGT nor CHT correlates perfectly with the valve temp on its own. But together they do. A sense of proportion is called for here. No, the valve temp does not exactly track EGT - I have never said that - but it does correlate very well. Yes, valve temp peaks slightly rich of EGT but that is because it is also inlfuenced by CHT. That is what the engineering literature tells us and it is what the NACA report shows us.
As long as you keep misrepresenting that I will keep correcting you.
Here again is the graph:
The position that you and Walter Atkinson have taken (and as far as I can tell it is an APS thing) is flat out wrong. Let me repeat your position "EGT and exhaust valve temperature are not in any way related". Wrong.
Except for the fact that valve temperature does not track EGT.
As long as you keep misrepresenting that I will keep correcting you.
Here again is the graph:
The position that you and Walter Atkinson have taken (and as far as I can tell it is an APS thing) is flat out wrong. Let me repeat your position "EGT and exhaust valve temperature are not in any way related". Wrong.
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Walter Atkinson:
Sort of yes.
No. The curve speaks for itself.
...but:
...and a couple of posts back:
...now the top secret NACA report does not show all of the issues
Well okay then let us be seeing this 1966 Lycoming clarification.
I won't ask for the Goulet stuff because you already said:
This isn't school Walter. By refusing to bring any supporting evidence out from behind the paywall of your course, your opinion on valves is unsupported and therefore not credible.
If one looks at the CHT and ICP curves and valve temp, one would see a nice correlation.
The EGT is a red herring.
The NACA report does not show all of the issues. These issues have been clarified quite nicely by Lycoming in 1966 and in the Carl Goulet Memorial Engine Test Facility.
We have hard data to prove that. The data came from a 1943 top secret NACA report done during WWII.
According to the 1943 NACA report referenced....This is definitive evidence that the two are NOT related.
...now the top secret NACA report does not show all of the issues
Well okay then let us be seeing this 1966 Lycoming clarification.I won't ask for the Goulet stuff because you already said:
Go the the APS website and sign up for the online course where 16+ hours of hard DATA are presented. It is the equivalent of a semester course, not a simple SAE "paper." Where I went to school, one had to pay for the education.
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Just for giggles, I curve fitted the EGT and Valve temperatures using third order polynomials.
Turns out the peak EGT is at a F/A ratio of 0.0649, which allowing for various uncertainties explains how Lycoming nominate the figure of 0.0648 as the F/A ratio peak EGT in their "Power from Fuel Flow" document.
I thought it was interesting.
I will bow out and let the belligerents continue to argue past each other.
Turns out the peak EGT is at a F/A ratio of 0.0649, which allowing for various uncertainties explains how Lycoming nominate the figure of 0.0648 as the F/A ratio peak EGT in their "Power from Fuel Flow" document.
I thought it was interesting.
I will bow out and let the belligerents continue to argue past each other.