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  #41  
Old 01-12-2014, 02:52 PM
jlk jlk is offline
 
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Default Misssing information

What engine is this valve from?

What engine monitoring device do you use? Does it have a LOP leaning mode?

What power setting do you normally run in cruise?

What was your last GAMI spread and when did you run it?

This information may help the discussion.
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  #42  
Old 01-12-2014, 06:12 PM
N427EF N427EF is offline
 
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Don Hull,
No problem and no appologies necessary.

Quote:
The answer to dilemma is simple. If you think LOP damages your engine just don't do it. Run ROP and be happy.
That would be simple but not an answer.

I certainly agree that flying frequently is both good for the engine as well as the pilot. I have no plans to abandon my LOP flying habits, in fact, since my last post I went out and burned 25 gallons of gas and 4 of us enjoyed a beautiful flight and an ok hamburger. LOP all the way CHT all less than 300F, granted the OAT was 50ish.

What bothers me is when an AP who has overhauled engines for 40 years tells me that burned valves show up in his shop with alarming frequency and those observations are fact not shop talk.

Quote:
2) Lycoming allows running continuously (in cruise) at "peak" EGT (in other words, as hot as your engine will make the EGT go)

3) lead, carbon, trash in the fuel and poor machining will prevent the exhaust valve from seating fully and limit the transfer of thermal load to the head, causing local overheating of the valve and failure.
I understand the heat exchange dynamics playing out in the valve/stem, valve guide and cylinder head assembly.

If running the engine almost anywhere is approved by Lycoming then what causes all those burned valves?

Quote:
So, does the gaseous makeup of the exhaust contribute to valve distress, or is it simply temperature (and/or the impurities which prevent the physically prevent the valve from transferring its heat load to the head/fins/air)?
The last quote is touching on my suspicions specifically concerning the chemical make up of exhaust gases resulting from an extremely lean mixture,
possibly contributing to valve/seat erosion before the onset of any valve stem/valve guide contamination. Simply put, I think the valve/seat gets ruined a little before the onset of lead and other byproduct deposits begin to deteriorate the valve stem/valve guide interface.
Once the heat exchange mechanism is ruined a quick deterioration of the valve face will follow.

I probably got it all backwards but it's hard to ignore prallel trends.
One, everyone flying LOP and two,an onslaught of burned valves showing up at overhaul shops.
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  #43  
Old 01-12-2014, 06:56 PM
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Toobuilder Toobuilder is offline
 
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Quote:
Originally Posted by BillL View Post
...Full load enrichment on the Vett is for power. More fuel across the catalyst will not BURN because there is NO OXYGEN. Many cars have this. It is not to "protect" the catalyst. Lets not get off track.
WARNING! Going off track for a second

Bill and Ross-

Here's what a well known GM tuner says about COTP:

...There are two safety protocols that GM has to save the cats. One is the COTP or cat over temp protection. When the exhaust temp reaches 1616F the first of three tables kicks in to add fuel and cool the exhaust temp. When the O2s reach a second threshold, you get another load of fuel, and finally as much as 20.5% more fuel in the third tier....


Since you guys called me out on that one, I figured I'd cite a supporting source. You can Google it if you'd like to know more.

...back to airplane stuff!
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  #44  
Old 01-12-2014, 07:33 PM
BillL BillL is offline
 
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Quote:
Originally Posted by Toobuilder View Post
WARNING! Going off track for a second

Bill and Ross-

Here's what a well known GM tuner says about COTP:

...There are two safety protocols that GM has to save the cats. One is the COTP or cat over temp protection. When the exhaust temp reaches 1616F the first of three tables kicks in to add fuel and cool the exhaust temp. When the O2s reach a second threshold, you get another load of fuel, and finally as much as 20.5% more fuel in the third tier....


Since you guys called me out on that one, I figured I'd cite a supporting source. You can Google it if you'd like to know more.

...back to airplane stuff!
Thanks for the update, sorry, my information is obviously lacking in all the details of current controls systems. I spent some years developing catalysts, but for diesels. I learned the auto techniques from my GM contacts in Detroit, and they probably did not use these algorithms back before OBDII. My main point was that automotive does not go high in oxygen content, A/F perturbation typically goes from 0-3% O2 (or so) and back due to the functioning of the catalyst for NOx CO and HC reduction. None of which is relevant to our LOP discussion.

OK, back to airplane stuff !
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and express it in numbers, you know something about it; but when you
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  #45  
Old 01-12-2014, 09:51 PM
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Ironflight Ironflight is offline
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Quote:
Originally Posted by N427EF View Post
What bothers me is when an AP who has overhauled engines for 40 years tells me that burned valves show up in his shop with alarming frequency and those observations are fact not shop talk.
BUt you counter that single A&P with 40 years of experience with Mike Busch - also an A&P - that says he's wrong. Observation by itself proves nothing - it just raises questions that need to be explained.

I've been running LOP with my carbureted engine on my -8 for 1700 hours now. We swapped jugs a couple of hundred hours ago due to a problem with defective rings, and the valves were pristine. Does that PROVE anything? Not really - except that those who say you can't run LOP with a carb need to re-think their statements.

I have been playing with flying machines for over forty years, and I can tell you that among pilots and owners I hear far fewer stories of engine problems today then thirty or twenty years ago. Again - observation of a small sample size (well, I watch a pretty broad spectrum of GA) that needs to be examined for truth.
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  #46  
Old 01-12-2014, 10:22 PM
jongurley jongurley is offline
 
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Quote:
Originally Posted by Ironflight View Post
BUt you counter that single A&P with 40 years of experience with Mike Busch - also an A&P - that says he's wrong. Observation by itself proves nothing - it just raises questions that need to be explained.

I've been running LOP with my carbureted engine on my -8 for 1700 hours now. We swapped jugs a couple of hundred hours ago due to a problem with defective rings, and the valves were pristine. Does that PROVE anything? Not really - except that those who say you can't run LOP with a carb need to re-think their statements.

I have been playing with flying machines for over forty years, and I can tell you that among pilots and owners I hear far fewer stories of engine problems today then thirty or twenty years ago. Again - observation of a small sample size (well, I watch a pretty broad spectrum of GA) that needs to be examined for truth.
Which follows the route of my question. On my Rv7a we are going with a 0-320 . and someone on page 3 of this thread said those with carbs don't need to try LOP, and i understand the theory, but then the same person(sorry forgot the name) says that Rich of peak is not were you want to be. So if you can't run LOP "safely" with a carbed engine and you don't want to be ROP, then were to you run it ????? full rich, Im not agreeing or disagreeing, I am realitivly new to flying (250hrs in cessnas and 150 in my Decathlon),, so Im just trying to get educated. We're about to finish our RV7A with 0-320 and I don't know whether we need a mixture knob or not after reading this thread lolol..
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  #47  
Old 01-12-2014, 11:35 PM
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RV10inOz RV10inOz is offline
 
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Quote:
Originally Posted by Ironflight View Post
BUt you counter that single A&P with 40 years of experience with Mike Busch - also an A&P - that says he's wrong. Observation by itself proves nothing - it just raises questions that need to be explained.

I've been running LOP with my carbureted engine on my -8 for 1700 hours now. We swapped jugs a couple of hundred hours ago due to a problem with defective rings, and the valves were pristine. Does that PROVE anything? Not really - except that those who say you can't run LOP with a carb need to re-think their statements.

I have been playing with flying machines for over forty years, and I can tell you that among pilots and owners I hear far fewer stories of engine problems today then thirty or twenty years ago. Again - observation of a small sample size (well, I watch a pretty broad spectrum of GA) that needs to be examined for truth.

PD is on the money.

There is too much BS being spread in this thread (not a lot compared to years ago) but the Old Wives Tales seem to persist even if in reduced numbers.


Quote:
Originally Posted by jongurley View Post
Which follows the route of my question. On my Rv7a we are going with a 0-320 . and someone on page 3 of this thread said those with carbs don't need to try LOP, and i understand the theory, but then the same person(sorry forgot the name) says that Rich of peak is not were you want to be. So if you can't run LOP "safely" with a carbed engine and you don't want to be ROP, then were to you run it ????? full rich, Im not agreeing or disagreeing, I am realitivly new to flying (250hrs in cessnas and 150 in my Decathlon),, so Im just trying to get educated. We're about to finish our RV7A with 0-320 and I don't know whether we need a mixture knob or not after reading this thread lolol..
Jon,

Take a look at the interactive red box graphic we have on the APS website. If you want to educate yourself this is about the best if not only one stop source of education.

By the way a good O-320 runs LOP no problem at all.

I have seen some comments about you can't run LOP with Carby's you can only do it with an engine monitor blah blah....... all of which is complete nonsense. Some things are better however with the above mentioned. In fact we believe the ROP pilot needs an EMS more than a LOP pilot does, and some have trouble getting their mind around that.

Hope that helps.
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  #48  
Old 01-13-2014, 06:43 AM
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rzbill rzbill is offline
 
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Quote:
Originally Posted by RV10inOz View Post
I have seen some comments about you can't run LOP with Carby's you can only do it with an engine monitor blah blah....... all of which is complete nonsense.
Pull it back until it runs rough and push it in a bit?

That eons old Lycoming mantra seems to echo the Big Mixture Pull.
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  #49  
Old 01-13-2014, 07:34 AM
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GalinHdz GalinHdz is offline
 
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Quote:
Originally Posted by rzbill View Post
Pull it back until it runs rough and push it in a bit?

That eons old Lycoming mantra seems to echo the Big Mixture Pull.
Even with the "fancy" EMS in my airplane, I still use the "pull it back until it runs rough and push it in a bit" method for engine leaning. Has been working for me for over 30yrs and the engine just loves it.

The "fancy" EMS lets me know if something is not where it should be and gives me good numbers to compare.

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  #50  
Old 01-13-2014, 09:26 AM
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Low Pass Low Pass is offline
 
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Quote:
Originally Posted by RV10inOz View Post
PD is on the money.

There is too much BS being spread in this thread (not a lot compared to years ago) but the Old Wives Tales seem to persist even if in reduced numbers.




Jon,

Take a look at the interactive red box graphic we have on the APS website. If you want to educate yourself this is about the best if not only one stop source of education.

By the way a good O-320 runs LOP no problem at all.

I have seen some comments about you can't run LOP with Carby's you can only do it with an engine monitor blah blah....... all of which is complete nonsense. Some things are better however with the above mentioned. In fact we believe the ROP pilot needs an EMS more than a LOP pilot does, and some have trouble getting their mind around that.

Hope that helps.
Many times, carbureted engines have inconsistent fuel distribution effectiveness. In this case, attempting to run LOP may put a cylinder or two in the wrong place attempting to "get there". Seen it many times. If you're fortunate enough to have a carb'd arrangement that provides good fuel distribution, then by all means, run LOP. But you need to be sure you know how each cylinder is responding (at least once, during the leaning process to know how the fuel distribution is occurring). And I've even seen a jet in a carb fail, throwing off the distribution radically. Been there, done that.

Last edited by Low Pass : 01-13-2014 at 09:32 AM.
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