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Lean side or rich side? Was: Pressure Carburetor?

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BobsV35B(at)aol.com
Guest

Posted: Tue Oct 02, 2007 8:13 am Post subject: Lean side or rich side? Was: Pressure Carburetor?

Good Morning Once More Don,   

 You asked: "And where is the crossover point?"  And I rather sluffed  over that point.  

  

 This may not directly address your specific question, but one possible  consideration might be the points made by Continental and Lycoming. 

  

 Lycoming occasionally tells us we can run lean of peak EGT when using less  than 75 percent power. 

  

 Continental tends to recommend that we not run lean of peak EGT unless we  are at 65 percent power or less.  Both of those figures are a bit tough to  pin down and both manufacturers have conflicting advice in various publications,  but it is a good starting point. 

  

 Neither manufacturer recommends lean side operation on very many of their  engines.

  

 While any engine can be run at full rated power on the lean side of peak  EGT (Automobiles do it often to meet EPA requirements) most of our aircraft  engines will be destroyed if we try it.

  

 So, could we say that the conservative "crossover point" is around  sixty-five percent power? 

  

 At that, or any lower, power, you will find it very difficult to do any  damage to the engine via the mixture control!

  

 Many more engines are damaged by not running rich enough at high power than  are damaged by running too lean at moderate to low cruise powers.

  

 Happy  Skies,



Old Bob

AKA

Bob Siegfried

Ancient Aviator

Stearman  N3977A

Brookeridge Air Park LL22

Downers Grove, IL 60516

630  985-8503



  

 In a message dated 10/1/2007 7:35:20 P.M. Central Daylight Time,  dongirod(at)bellsouth.net writes:

  	  Quote: 	
		  And    where is the crossover point. 	


 





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John Vormbaum

Joined: 21 Aug 2006
Posts: 273
Location: SF Bay Area, CA

Posted: Tue Oct 02, 2007 11:05 am Post subject: Lean side or rich side? Was: Pressure Carburetor?

Bob,



IIRC from John Deakin's articles, there is only a very narrow range of 

EGT that can cause damage to any engine at any power setting, right? I 

took Deakin's writings to heart a few years ago, and with the 

installation of a JPI engine monitor in my Commander, I run LOP in 

pretty much all phases of flight except climbout. At cruise, since I'm 

turbocharged, I can run at 75% power up high and run LOP while at that 

power setting. I have one engine that is a bit past TBO and one that is 

about 1/2 way to TBO. Both engines run very well LOP. Both engines run 

very cool. I'm always in a hurry, so I don't care too much about saving 

fuel, but now, LOP, I'm saving avgas too.



I remember that the "big mixture pull" upon reaching cruise altitude is 

something that should be done rather quickly to get past the potential 

high cyl pressure/detonation point, but other than that, there's not 

much to worry about.



I guess what I'm saying is that based on empirical data & a few years 

experience, and running an engine past TBO, I'll have to disagree with 

Lycoming that "LOP operation is bad for your Lycoming engine!" as I 

think I have proven otherwise. In about 600 hrs. of flight, I've only 

changed a cylinder on each engine, and that was just this year. I don't 

think an engine cares WHY it's cool, as long as it runs cool . Whether 

cooled by air or excess fuel, it doesn't seem to matter. Also, when LOP, 

the peak cylinder pressure point happens later in the cycle, putting far 

less pressure on pistons etc.



I've had my 500B since 1999. Prior to the JPI, I would do the "lean it 

til it gets rough, then push forward a skosh on the red levers" and that 

worked fine. In fact, once I got my JPI in, it confirmed that that 

strategy results in LOP operation, so it looks like I've been running 

LOP for the whole time I've had the airplane. I also used to lean til 

rough, push a tad forward, and then shut off a mag. If it ran fine on 

both mags but rough on one (with rpm drop), I could pretty much assume I 

was running it as lean as possible for that power setting.



Also, I'm fuel injected, so I think I can count on more consistency with 

fuel distribution than most carbureted engines.



Cheers,



/John



BobsV35B(at)aol.com wrote:

 	  Quote: 	
		   Good Morning Once More Don,

  

 You asked: "And where is the crossover point?"  And I rather sluffed 

 over that point. 

  

 This may not directly address your specific question, but one possible 

 consideration might be the points made by Continental and Lycoming.

  

 Lycoming occasionally tells us we can run lean of peak EGT when using 

 less than 75 percent power.

  

 Continental tends to recommend that we not run lean of peak EGT unless 

 we are at 65 percent power or less.  Both of those figures are a bit 

 tough to pin down and both manufacturers have conflicting advice in 

 various publications, but it is a good starting point.

  

 Neither manufacturer recommends lean side operation on very many of 

 their engines.

  

 While any engine can be run at full rated power on the lean side of 

 peak EGT (Automobiles do it often to meet EPA requirements) most of 

 our aircraft engines will be destroyed if we try it.

  

 So, could we say that the conservative "crossover point" is around 

 sixty-five percent power?

  

 At that, or any lower, power, you will find it very difficult to do 

 any damage to the engine via the mixture control!

  

 Many more engines are damaged by not running rich enough at high power 

 than are damaged by running too lean at moderate to low cruise powers.

  

 Happy Skies,



 Old Bob

 AKA

 Bob Siegfried

 Ancient Aviator

 Stearman N3977A

 Brookeridge Air Park LL22

 Downers Grove, IL 60516

 630 985-8503

  

 In a message dated 10/1/2007 7:35:20 P.M. Central Daylight Time, 

 dongirod(at)bellsouth.net writes:



     And where is the crossover point.





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BobsV35B(at)aol.com
Guest

Posted: Tue Oct 02, 2007 11:19 am Post subject: Lean side or rich side? Was: Pressure Carburetor?

Good Afternoon John,   

 It seems you have done broke de code!!<G>

  

 The turbo-charger (or many other superchargers for that matter) does allow  operation at quite high powers when lean of peak. 

  

 The key is a thorough understanding of the combustion process combined with  a method to evaluate the efficacy of the method chosen to attain the desired  state.

  

 Glad you found the truth!

  

 Happy  Skies,



Old Bob

AKA

Bob Siegfried

Ancient Aviator

Stearman  N3977A

Brookeridge Air Park LL22

Downers Grove, IL 60516

630  985-8503



  

 In a message dated 10/2/2007 2:06:53 P.M. Central Daylight Time,  john(at)vormbaum.com writes:

  	  Quote: 	
		  I guess    what I'm saying is that based on empirical data & a few years    

experience, and running an engine past TBO, I'll have to disagree with    

Lycoming that "LOP operation is bad for your Lycoming engine!" as I    

think I have proven otherwise. In about 600 hrs. of flight, I've only    

changed a cylinder on each engine, and that was just this year. I don't    

think an engine cares WHY it's cool, as long as it runs cool . Whether    

cooled by air or excess fuel, it doesn't seem to matter. Also, when LOP,    

the peak cylinder pressure point happens later in the cycle, putting far    

less pressure on pistons etc.

	


 





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  [quote][b]

steve2(at)sover.net
Guest

Posted: Tue Oct 02, 2007 3:02 pm Post subject: Lean side or rich side? Was: Pressure Carburetor?

John,



I've found pretty quickly I've lost a mag when I feel some roughness and all 

of a sudden see a spike in EGT/CHT. Sure enough, I'll switch between mags 

and find a dead one. Interesting coming home with one engine lean, and one 

engine rich. Both have similar EGT/CHT, but one is swilling fuel, and one 

isn't........



Steve

---

John Vormbaum

Joined: 21 Aug 2006
Posts: 273
Location: SF Bay Area, CA

Posted: Tue Oct 02, 2007 3:42 pm Post subject: Lean side or rich side? Was: Pressure Carburetor?

I never thought about the diagnostic bonus (for bad mags) of running the 

engines where I do, but that sounds like a handy fringe benefit!



/J



Steve (at) Col-East wrote:

[quote] 

 <steve2(at)sover.net>



 John,



 I've found pretty quickly I've lost a mag when I feel some roughness 

 and all of a sudden see a spike in EGT/CHT. Sure enough, I'll switch 

 between mags and find a dead one. Interesting coming home with one 

 engine lean, and one engine rich. Both have similar EGT/CHT, but one 

 is swilling fuel, and one isn't........



 Steve

 ---

BobsV35B(at)aol.com
Guest

Posted: Tue Oct 02, 2007 4:06 pm Post subject: Lean side or rich side? Was: Pressure Carburetor?

Good Evening Steve,   

 Just out of curiosity, what was the occasion that had you operating one  engine on the lean side and the other one on the rich side!

  

 Happy  Skies,



Old Bob

AKA

Bob Siegfried

Ancient Aviator

Stearman  N3977A

Brookeridge Air Park LL22

Downers Grove, IL 60516

630  985-8503



  

 In a message dated 10/2/2007 6:03:46 P.M. Central Daylight Time,  steve2(at)sover.net writes:

  	  Quote: 	
		  I've    found pretty quickly I've lost a mag when I feel some roughness and all 

of    a sudden see a spike in EGT/CHT. Sure enough, I'll switch between mags 

and    find a dead one. Interesting coming home with one engine lean, and one    

engine rich. Both have similar EGT/CHT, but one is swilling fuel, and one    

isn't........



Steve

	


 





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  [quote][b]

steve2(at)sover.net
Guest

Posted: Wed Oct 03, 2007 2:54 am Post subject: Lean side or rich side? Was: Pressure Carburetor?

Bob,

  

 In the past couple years we've had a number of mag failures. The last time  a coil went bad. We go through them every 500 hours or so, but still have a  problem now and again. Once I see the loss in CHT/EGT, or feel it, I goose that  side to rich so I'm not running cylinders where I don't want them, and work the  rest of the day with the split.

  

 I don't know what other folks have found, but we've found one thing about  LOP, and that is it's very intolerant of any faults..... Ignition,  induction..... Everything needs to be in tip top shape. I think a lot of things  you might not notice otherwise when running these things on the rich side, shows  up LOP.

  

 The six probe EGT is an amazing gizmo. I've looked over and seen a spike in  one jug and thought, now what? Cycle through the mags and find a bad plug, and  confirm it on the ground.

  

 A cracked flange on an induction tube.... Shows up on the EGT.

  

 A lot of this stuff you can feel, even when its really subtle, but the EGT  helps you find it.

  

 Steve

 [quote]   ---

BobsV35B(at)aol.com
Guest

Posted: Wed Oct 03, 2007 5:08 am Post subject: Lean side or rich side? Was: Pressure Carburetor?

Good Morning Steve,   

 Your experience directly parallels mine. The modern engine monitor  consisting of all cylinder EGT and CHT indications combined with a good  electronic fuel flow is not only a great aid in diagnosing problems, but it  really helps train us in how the engine really operates!

  

 The ignition system needs to be in excellent shape. It is not unusual to  find brand new spark plugs that fail a high power lean of peak magneto  check right out of the box.  I now consider my inflight, high power,  magneto check to be much more important than the one traditionally performed  before takeoff.

  

 It is a fact that many engines which do not run well lean of peak will  be found to have small induction leaks. 

  

 With an unsupercharged engine a comparison of a careful lean  check performed at altitude and one done down low will generally find that  leak.

  

 Do you use a lean spread check such as the one recommended by the GAMI  folks?

  

 While I have been running on the lean side and working to balance my fuel  nozzles and/or intake systems for well over fifty years, I had never thought of  doing their lean check procedure before I bought my GAMI balanced fuel nozzles.  That knowledge alone was well worth the purchase price.

  

 I still feel very comfortable struggling along without a good engine  monitor, but it is one of the first places that I would spend my money if I  bought a 'new to me' airplane. It is a lot more than just a nice toy.

  

 The saving of fuel via more precise control is nice, but much more  important is the ability to catch minor engine problems easily and to be able to  pin point the location of those impending difficulties.

  

 Having said all that, this is why I asked the question: 

  

 Did you consider running your engine on the lean side after that one  magneto failed? All that running on one mag does is retard the point  of peak combustion pressure. Kinda like retarding the spark just a bit.  Shouldn't be any problem at all. 

  

 If you wanted to pick the power back up a bit, rechecking the peak on the  one magneto and going on from there to your normal lean operating point should  work just fine. 

  

 Any thoughts?

  

 Happy  Skies,



Old Bob

AKA

Bob Siegfried

Ancient Aviator

Stearman  N3977A

Brookeridge Air Park LL22

Downers Grove, IL 60516

630  985-8503



  

 In a message dated 10/3/2007 5:55:06 A.M. Central Daylight Time,  steve2(at)sover.net writes:

  	  Quote: 	
		     I don't know what other folks have found, but we've found one thing about    LOP, and that is it's very intolerant of any faults..... Ignition,    induction..... Everything needs to be in tip top shape. I think a lot of    things you might not notice otherwise when running these things on the rich    side, shows up LOP.

    

   The six probe EGT is an amazing gizmo. I've looked over and seen a spike    in one jug and thought, now what? Cycle through the mags and find a bad plug,    and confirm it on the ground.

    

   A cracked flange on an induction tube.... Shows up on the EGT.

    

   A lot of this stuff you can feel, even when its really subtle, but the    EGT helps you find it.

    

   Steve

	


 





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  [quote][b]

steve2(at)sover.net
Guest

Posted: Wed Oct 03, 2007 6:37 am Post subject: Lean side or rich side? Was: Pressure Carburetor?

Old Bob,

  

 Affirmative on the GAMI test.

  

 We're pretty close to perfect on fuel injection balance, but not quite  there. We've got the smallest injectors GAMI will give us on number 1, and the  largest on 5 and 6. But pulling the mixture back has the fire going out in  number 5 first, on both engines.

  

 We've speculated that there is something about this engine installation on  the Commander that is harder to balance. The spider is all the way forward, and  number 5 has the longest and kinkiest run of the fuel injection  line. 

  

 We did the test with having each of the injectors piddle into a Coke  bottle. 5 lags just a little behind the others. (As an aside, a couple years ago  that's how we found the rebuilt engine's fuel pump had had a chunk of thread  come off and run through the pump, distributing chunks into the spider.) We even  found the fuel injection line had nipple ends with different internal diameters,  and changed the long number 5 and 6 lines to match the new style.  It  helped, but didn't totally cure it.

  

 Pulling the mixture, way way back, or losing a mag, has the engine  (especially our left engine) run with a little bit of vibes. I've got sitting on  my desk a left side intake gasket that obviously wasn't making the same  good contact all the way around. We just last week replaced the last of the old  chintzy intake tubes, with newer heavier gauge ones. I'm eager to get in the air  to see if we've had an undiagnosed small intake leak.

  

 Steve

  

  

  

  

 [quote]   ---

BobsV35B(at)aol.com
Guest

Posted: Wed Oct 03, 2007 6:53 am Post subject: Lean side or rich side? Was: Pressure Carburetor?

Good Morning Steve

  

 It is an interesting new world when we get good instrumentation, isn't  it?

  

 I am not at all familiar with the intake tubes on the 540. Is there any  possibility of an "Occult"  (as George calls it) fuel transfer with your  intake pipes?

  

 Always something new to be learned.

  

 Happy  Skies,



Old Bob

AKA

Bob Siegfried

Ancient Aviator

Stearman  N3977A

Brookeridge Air Park LL22

Downers Grove, IL 60516

630  985-8503



  

 In a message dated 10/3/2007 9:39:05 A.M. Central Daylight Time,  steve2(at)sover.net writes:

  	  Quote: 	
		     We did the test with having each of the injectors piddle into a Coke    bottle. 5 lags just a little behind the others. (As an aside, a couple years    ago that's how we found the rebuilt engine's fuel pump had had a chunk of    thread come off and run through the pump, distributing chunks into the    spider.) We even found the fuel injection line had nipple ends with different    internal diameters, and changed the long number 5 and 6 lines to match the new    style.  It helped, but didn't totally cure  it.

	


 



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n395v

Joined: 10 Jan 2006
Posts: 450

Posted: Thu Oct 04, 2007 6:07 pm Post subject: Re: Lean side or rich side? Was: Pressure Carburetor?

Video inside a working cylinder



http://video.google.com/videoplay?docid=-5815350492893860613

_________________
Milt

yourtcfg(at)aol.com
Guest

Posted: Thu Oct 04, 2007 6:37 pm Post subject: Lean side or rich side? Was: Pressure Carburetor?

WAY COOL!!  jb

   	  Quote: 	
		   	  Quote: 	
		  	
	


 

 

 --

nico(at)cybersuperstore.c
Guest

Posted: Thu Oct 04, 2007 10:52 pm Post subject: Lean side or rich side? Was: Pressure Carburetor?

That's very nice, Milt.

Did you notice how far BTDC the ignition fires? I was looking for valve

overlap but the footage cuts at the precise moment that it should happen.

Although there is one frame where the inlet valve starts to open while the

exhaust valve is completely closed, indicating that his particular engine

doesn't have valve overlap. That technique to increase power without any

penalty somewhere else, has been developed in the late 60's or so and then

only in very exclusive high-performance engines. My guess is that this

engine is of a pre-1960's design; it is probably an aircraft engine. 

Nico



--

steve2(at)sover.net
Guest

Posted: Fri Oct 05, 2007 3:55 am Post subject: Lean side or rich side? Was: Pressure Carburetor?

Where are the gerbils?



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