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  #21  
Old 08-09-2011, 07:53 AM
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Toobuilder Toobuilder is offline
 
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Quote:
Originally Posted by Moura View Post
So it seems to me that as long as you have cool CHT you are safe...
It seems that this is what most of the experts are saying... Also, remember that Deakin is discussing big bore, turbo engines, and many of our low compression Lycs can't detonate even if you try.
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  #22  
Old 08-09-2011, 08:37 AM
David-aviator David-aviator is offline
 
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Originally Posted by Toobuilder View Post
Good point Dan. To expand on that, it has been argued by some that it is not even possible to cause a naturally aspirated Lycoming to detonate. While Im sure that there are some extreme examples (a high compression engine on mogas, perhaps), the fact that our fleet is not falling out of the air on a regular basis has a lot more to do with engine design than our collective skill at engine management. Lets face it, were pilots if there is a way to screw something up, well find it! I dont know for sure, but perhaps detonation in most of our engines is like the boogey man mostly a figment of our imagination and the only thing we really need to worry about is CHT management?

For the record, does anyone have firsthand knowledge of a N/A Lycoming failing due to detonation?
And you make a good point, Michael. Perhaps there are few instances of failure due to detonation because CHT is a limiting factor in high power situations - pilots are using fuel flow to augment cooling.

All the data assembled here at the beginning of this thread is most impressive, I've read bits and pieces of it over the years but have not seen it all so well presented. Thanks, Hans.

I like Mike Busch's take on all this regarding the red box, it is a bit more simplified. He recommends using take off EGT as the reference and leaning to it during climb. Maybe Deakins does the same, I have not read the entire post.

This is interesting stuff.
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  #23  
Old 08-09-2011, 08:46 AM
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Deakin calls it TARGET EGT, its the only way to climb

And yes the low compression as you call it, or standard LYC can be run in detonation.

Go try it some time with all EGT and CHT probes and a good display, it will make your eyes
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  #24  
Old 08-09-2011, 08:51 AM
RV8R999 RV8R999 is offline
 
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"John Deakin is a 35,000-hour pilot who worked his way up the aviation food chain via charter, corporate, and cargo flying; spent five years in Southeast Asia with Air America; 33 years with Japan Airlines, mostly as a 747 captain; and now flies the Gulfstream IV for a West Coast operator.

He also flies his own V35 Bonanza (N1BE) and is very active in the warbird and vintage aircraft scene, flying the C-46, M-404, DC-3, F8F Bearcat, Constellation, B-29, and others. He is also a National Designated Pilot Examiner (NDPER), able to give type ratings and check rides on 43 different aircraft types."

I see Mr. Deakin is a very experienced pilot but what about his engineering/test background? Maybe this short bio doesn't include his technical expertise or background - anybody know?
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  #25  
Old 08-09-2011, 09:14 AM
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Quote:
Originally Posted by RV10inOz View Post
...And yes the low compression as you call it, or standard LYC can be run in detonation...
There are quite a few experts who would disagree with you... Not under "normal" circumstances anyway.

Also, while I'm not among the "experts", I do know that I have never seen detonation as evidenced by runaway CHT on any Lycoming I've flown - and I have done some dumb things with the mixture control over the years.

Just my (nearly) undeducated opinion here, but I'll bet if the engine has an STC or is otherwise capable of operating on the watered down Mogas, it's nearly impossible to induce detonation in that engine on 100LL.
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Last edited by Toobuilder : 08-09-2011 at 09:18 AM.
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  #26  
Old 08-09-2011, 09:17 AM
Darren S Darren S is offline
 
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Default My 2 cents

I read this article several months ago and was all psyched to go try LOP. I fly a -7 with a Superior IO-360 and C/S prop. I don't have GAMI injectors.

I usually run 65% and lean to 25 ROP on the first cylinder to peak. My field elevation is 3300 and CHT's are 340 in cruise.

My findings: it was very difficult to get all cylinders LOP. Some were, others were right at peak or ROP. And as soon as you change altitude everything changes. I would spend so much time staring at the EFIS I was afraid I was going to fly into something!

I don't like an engine that is borderline "rough" running. He says it may not hurt anything but I don't like the feel. The fuel economy ain't worth it. For me.

I said forget it and went back to my old way.

As for carbon build up and fouled plugs....... I add Decalin Runup to every tank of 100LL and lean the engine on start up and taxi and of course cruise.

On inspection of the lower plugs recently they were burning very well with no lead balls on the electrodes. This after idling for an hour at OSH waiting to depart.

LOP ain't for me.

Darren
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  #27  
Old 08-09-2011, 09:23 AM
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Quote:
Originally Posted by Darren S View Post
...I don't like an engine that is borderline "rough" running...
Ignition quality has a huge impact on "roughness". Before the dual Pmags I could not even get to 30 LOP without noticable rough operation. Without any other changes, I can do 150+ LOP now (before stumble)
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  #28  
Old 08-09-2011, 09:33 AM
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RV8RIVETER RV8RIVETER is offline
 
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Quote:
Originally Posted by Darren S View Post
I don't have GAMI injectors.

Darren
Lucky for us Lycoming opertors, we don't need GAMI injectors on a Lycoming. Lycoming injectors have removable restrictors that come in different sizes. You can search injector matching for the info on how to do it.
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  #29  
Old 08-09-2011, 09:54 AM
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All it takes is a call to Don at AFP and run their test cases. Send them your data and they will provide a recomendation on how to balance your injectors.
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  #30  
Old 08-09-2011, 10:01 AM
Moura Moura is offline
 
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Since Don from AFP was mentioned, I did replace my restrictors and they were perfect. Only replaced 3 for 25 dollars (I think that is what I paid) each.
But you know what puzzles me, Don mentioned he would never run not even an inch above 24MAP when LoP!! Should I be confused?
Moura

Last edited by Moura : 08-09-2011 at 10:21 AM.
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