Antoine wrote:I did not understand you "Deacons red fin" sentence and Google did not help. Can you explain please? Maybe a separate thread to avoid the drift?
He's referring to John Deakin's well-regarded series of articles on how to operate your engine, and in particular how to avoid operation within the "Red Box":
I also highly recommend Deakin's articles. Even if you have deep-seated philosophical issues with running LOP, you will still learn tons of useful information about what happens inside of your engine, and why many of the OWT's (Old Wive's Tales) are not valid! To me, his arguments for not running your engine in the "Red Box" just make sense.
To me this sounds like black magic.
Please help me understand this.
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The Dangerous Red Box
Just where is that "red box" I keep talking about? Some rough numbers, good (that is to say, BAD) for most of these engines -- these are "no fly zones," DO NOT set the mixture between them:
Red Box = No Fly Zone
At and below about 60% power, there is no red box. Put the mixture wherever you want it.
At about 65% power or so, 100ºF ROP to Peak.
At about 70%, 125ºF ROP to 25ºF LOP.
At about 75%, 180ºF ROP to 40ºF LOP.
At about 80%, 200ºF ROP to 60ºF LOP.
All those numbers are approximate! Please don't start splitting hairs, here!
You probably don't want to run your engine between those mixture settings. If you do, you are running very high peak pressures inside the combustion chambers, and that peak pressure is occurring too close to top dead center.
There's a chance you read too fast, and missed this very important point, so let me put it another way:
Outside the Box
At 65% power, use richer than 100 ROP, or leaner than peak EGT.
At 70%, use richer than 125ºF ROP, or leaner than 25ºF LOP.
At 75%, use richer than 180ºF ROP, or leaner than 40ºF LOP.
At 80%, use richer than 200ºF ROP, or leaner than 60ºF LOP.
(On most of these engines, with a properly set mixture at full rich, at sea level, full power, the EGT ends up at about 250ºF ROP, with some as high as 300ºF ROP.)
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I usually run my engine at Peak EGT except when doing performance tests where I find best power around 50 ROP. Is it going to die on me sometime soon (scared voice)?
I was gonna type a responce up but it would be long enough that nobody would read it. Best to follow the links above and try to digest it. My best advice is to log onto GAMIS site and take the APC engine management course. They have an on line version and it's money well spent. It does a great job explaining how all this fits together.
Jeff
PRIVATE PILOT, IFR
2005 DA40 SOLD
2006 SR22, A/C, TKS, AVIDYINE PFD/MFD, IFD 540/440, AXP322 remote ADS-B TRANSPONDER, AMX240 AUDIO PANEL, MLB100 ADS B in.
168 KTAS 9,000' msl @ 13.6 gph LOP. 1005 pound useful load.
Honestly I have started to read some of the articles and gave up. The writer may be an engine guru but his way of communicating his expertise irritates me - I cannot learn from people like him. Thank you nevertheless.
My engine unfortunately hates LOP, so I cannot play this game.
It does sound happy between 50 ROP and peak EGT. That's what I do... and if compressions are an indication, the engine is still "as new" after 650 hours.
Honestly I have started to read some of the articles and gave up. The writer may be an engine guru but his way of communicating his expertise irritates me - I cannot learn from people like him. Thank you nevertheless.
My engine unfortunately hates LOP, so I cannot play this game.
It does sound happy between 50 ROP and peak EGT. That's what I do... and if compressions are an indication, the engine is still "as new" after 650 hours.
Hi Antoine, the redbox concept is not at all just for LOP operations. It is very important for ROP operations too. In the redbox concept, 50rop is almost the worst place to run your engine in terms of longevity. Is that 50rop at 65% or at 75% - it makes a difference as to how hard it is on the engine. A Lycoming IO360 will not likely suffer the more dire consequences of running in the middle of the redbox - the worst being detonation, but it could still make for an unhappy engine (so they say). 650 hours is not very long to tell the difference between good operations and better operations. When your engine has 1400 maybe 1500 hrs then I would be worried that you would be clipping the longevity.
But the Lycoming io360 is supposed to be one of the most bullet proof engines out there, so it will maybe go fine no matter what you do. I am flying behind a continental TSIO520NB now and the bigger the engine, and turbo charging, then the more important for longevity - but also safety (lest detonation) that we learn the redbox concept.
If you are planning on running ROP, then the punchline of the redbox concept is that you likely need to be running more rich, meaning a bit more fuel at any given setting. Example - if you are running 50 rich of peak egt and that is at 65% power, then to stay out of the redbox you increase the fuel flow until you are at 100 rich of peak.
Erik wrote:
If you are planning on running ROP, then the punchline of the redbox concept is that you likely need to be running more rich, meaning a bit more fuel at any given setting. Example - if you are running 50 rich of peak egt and that is at 65% power, then to stay out of the redbox you increase the fuel flow until you are at 100 rich of peak.
Thanks Erik
Actually this is just the missing answer to my question "why are you running such low EGTs" in another thread. I am puzzled that no one replied "Red Box" there.
This said, while I sincerely appreciate the effort you and others put in explaining this, I will for once express a very bold contrarian opinion. Running an IO-360 so over rich is a no-go to me.
I run it at peak EGT for best economy and at the best power point (about 50 ROP) for ... best power.
I cannot afford to throw fuel away and there is a huge difference between 50 ROP and what the red box rule wants. Plus the engine sounds really fine at 50 ROP.
I have no significant experience with Continentals, and I suspect this whole red box thing is a way of working around the primitive turbo systems we have in GA...
Erik wrote:
If you are planning on running ROP, then the punchline of the redbox concept is that you likely need to be running more rich, meaning a bit more fuel at any given setting. Example - if you are running 50 rich of peak egt and that is at 65% power, then to stay out of the redbox you increase the fuel flow until you are at 100 rich of peak.
Thanks Erik
Actually this is just the missing answer to my question "why are you running such low EGTs" in another thread. I am puzzled that no one replied "Red Box" there.
This said, while I sincerely appreciate the effort you and others put in explaining this, I will for once express a very bold contrarian opinion. Running an IO-360 so over rich is a no-go to me.
I run it at peak EGT for best economy and at the best power point (about 50 ROP) for ... best power.
I cannot afford to throw fuel away and there is a huge difference between 50 ROP and what the red box rule wants. Plus the engine sounds really fine at 50 ROP.
I have no significant experience with Continentals, and I suspect this whole red box thing is a way of working around the primitive turbo systems we have in GA...
I do believe in the testing they did behind the redbox theory, but it is just that and to each his own and I do not suggest you shouldn't runs yours as you see fit. I can say that it is a longevity thing as well, so my io360 sounded great too at any setting whatsoever right up until idle cut off (so even deep into lean of peak) since it was well tuned with gami injectors. So sound alone is not enough.
If the redbox theory is right, then saving some on fuel might cost in terms of engine longevity down the road. Then again at European fuel costs - I guess you can calculate exactly how much missed off of tbo you could afford and still come out ahead - even if it is true.
I follow the redbox theory - yes on my big continental - but to me that means if rop then rich enough, and if lean of peak then lean enough, depending on specific percent power settings.
