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02-01-2011, 07:59 AM
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Join Date: Oct 2006
Location: Garden City, Tx
Posts: 5,145
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Quote:
Originally Posted by bignose
Now, most important to know, where is really the so tamed Red Box to be avoided ?
To know the right thing to do, we should first know what NOT to do under no sircumstances, right ?
Lycoming recomends Peak under 75% and that's it ! So, where is the Edge?
That's the question... Where is RED BOX ?
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Here you go - read these columns by John Deakin. He does a much better job of explaining it than I do.
http://www.avweb.com/news/pelican/182544-1.html
__________________
Greg Niehues - SEL, IFR, Repairman Cert.
Garden City, TX VAF 2020 dues paid 
N16GN flying 700 hrs and counting; IO360, SDS, WWRV200, Dynon HDX, 430W
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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02-01-2011, 09:32 AM
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Join Date: Sep 2010
Location: Sao Paulo, Brasil
Posts: 72
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So, now it's explained !
Quote:
Originally Posted by airguy
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Good reading, thanks a lot !
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02-02-2011, 05:50 PM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Quote:
Originally Posted by bignose
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The article seems to focus on LOP operation of turbocharged models.
I'm not advocating one view or the other. Personally I would like more data. I have written the Thunderbolt folks at Lycoming and asked when they will have a complete engine power chart available for my IO-390. Unlike power charts for other models, the current IO-390 chart has no detonation limit line.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
Last edited by DanH : 02-02-2011 at 05:55 PM.
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02-03-2011, 08:58 AM
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Join Date: Oct 2006
Location: Garden City, Tx
Posts: 5,145
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Quote:
Originally Posted by DanH
The article seems to focus on LOP operation of turbocharged models.
I'm not advocating one view or the other. Personally I would like more data. I have written the Thunderbolt folks at Lycoming and asked when they will have a complete engine power chart available for my IO-390. Unlike power charts for other models, the current IO-390 chart has no detonation limit line.
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Agreed - I'm a data kind of guy. Deakin has it, Lycoming does too - but Deakin shares it and Lycoming won't. Secrecy doesn't buy much faith.
__________________
Greg Niehues - SEL, IFR, Repairman Cert.
Garden City, TX VAF 2020 dues paid 
N16GN flying 700 hrs and counting; IO360, SDS, WWRV200, Dynon HDX, 430W
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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02-03-2011, 09:21 AM
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Join Date: Aug 2006
Location: Taylor Texas
Posts: 811
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Wottsa matta U?
A balanced fuel delivery system is an absolute requirement for LOP ops, and I will assume you have made the adjustments to balance your system. The rest is easy.
Simply put, the Red Box contains the conditions that will generate 400F+ CHTs. 400F+ CHTs are part of the requirement to generate pre-ignition, which is a requirement to generate thermal runaway. Thermal runaway generates a lot of repair bills...especially when 14 cylinders are involved.
So, keep your CHTs under 400F and you are good to go. This may be an over-simplification, but it is also pretty easy to remember.
MP/PM combo is not really something you have to pay close attention to - LOP @ max available power will work fine - just stay out of the Red Box, either ROP or LOP. Turbo'ed engines (their Red Box indicator is TIT) run along happily @30"+ all day - your NA engine will do the same.
The Big Mixture Pull involves going thru the Red Box, but the idea is to do it quick enough to keep the CHT below 400F. Once you get a feel for the fuel flow required to be LOP at the power setting in place when you make the BMP, it's easy. Get 'er close, and tweak it from there.
It was once explained to me like this: "Sonny boy, you can cool your engine with fuel, or air. Air is cheaper...."
Carry on!
Mark
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02-03-2011, 11:35 AM
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Join Date: Jan 2005
Location: Louisville, Ga
Posts: 7,840
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Can you clarify some, Mark...
I read about the "Big pull" but it's difficult to know when to stop pulling, or do you keep on 'til the engine stumbles, the way we used to do Skyhawks and 150's?
Since Don at Airflow and I balanced the injectors pretty closely, I screw the mixture out and allow enough time to see a change and keep going until the first cylinder peaks and keep on leaning with the Dynon in "Lean" mode. So apparently, I reach peak and it stays there for a few seconds but my CHT's never go over 400F, while I continue on to LOP on all cylinders.
I don't think that I stay at peak long enough to do any damage because I'm usually a little under 23" anyway...around 22.8"
Thanks,
__________________
Pierre Smith
RV-10, 510 TT
RV6A (Sojourner) 180 HP, Catto 3 Bl (502Hrs), gone...and already missed
Air Tractor AT 502B PT 6-15 Sold
Air Tractor 402 PT-6-20 Sold
EAA Flight Advisor/CFI/Tech Counselor
Louisville, Ga
It's never skill or craftsmanship that completes airplanes, it's the will to do so,
Patrick Kenny, EAA 275132
Dues gladly paid!
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02-03-2011, 01:31 PM
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Join Date: Aug 2006
Location: Taylor Texas
Posts: 811
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it takes a litel practice
Hey Pierre:
No worries - if your FF indicator is quick enough, you simply pull until it gets close to the number you know is correct. I was so familiar with Ol' 84 that I did it by volume (listened for the slight decrease in the exhaust note); not quite there with the 550 beast yet...so I watch the FF reading. I don't use the leaning feature anymore, as I move the mix lever too quickly, and the EGT doesn't get to peak. Could be that the system (Dynon), or the sensors, are too slow? This wouldn't be the case if the EGT never gets to peak....
BTW if your injectors are VERY closely matched, the engine never gets rough - it simply quits. Try it once -- your passengers will think it's very funny! NOT.
Carry on!
Mark
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02-03-2011, 02:57 PM
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Join Date: Oct 2006
Location: Garden City, Tx
Posts: 5,145
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In my C-172 with IO360 and matched Gami-jectors, it never gets rough. I simply grab the mixture and pull it until the RPM begins to sag, then fine-tune it. From ROP to LOP is maybe 2 seconds, not even enough time for the EGT's to react. With a FP prop, I level out at my desired cruise altitude, and as the engine RPM reachs and exceeds 2550 with increasing airspeed I do the big pull.
With a good mixture distribution from well-matched injectors, you never feel the roughness from leaning - you just lose power. I can make my engine run smoothly at WOT and 2000 rpm just by leaning it, and it runs way cool. Standard cruise for me is 6k-8k, WOTLOP and control power by mixture to maintain the desired RPM. The throttle stays wide open from takeoff until descent, at about 5k' I go back to ROP and control power with the throttle. I normally true out 118knots on 7.7-8.0 gph.
__________________
Greg Niehues - SEL, IFR, Repairman Cert.
Garden City, TX VAF 2020 dues paid 
N16GN flying 700 hrs and counting; IO360, SDS, WWRV200, Dynon HDX, 430W
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
Last edited by airguy : 02-03-2011 at 03:00 PM.
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02-03-2011, 03:06 PM
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Join Date: Aug 2006
Location: Taylor Texas
Posts: 811
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Quote:
Originally Posted by airguy
In my C-172 with IO360 and matched Gami-jectors, it never gets rough. I simply grab the mixture and pull it until the RPM begins to sag, then fine-tune it. From ROP to LOP is maybe 2 seconds, not even enough time for the EGT's to react. With a FP prop, I level out at my desired cruise altitude, and as the engine RPM reachs and exceeds 2550 with increasing airspeed I do the big pull.
With a good mixture distribution from well-matched injectors, you never feel the roughness from leaning - you just lose power. I can make my engine run smoothly at WOT and 2000 rpm just by leaning it, and it runs way cool. Standard cruise for me is 6k-8k, WOTLOP and control power by mixture to maintain the desired RPM. The throttle stays wide open from takeoff until descent, at about 5k' I go back to ROP and control power with the throttle. I normally true out 118knots on 7.7-8.0 gph.
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I gotta ask - is that the Lyc 360 or the TCM 6 cyl unit? With your methods, you'll never wear out that throttle cable!
Carry on!
Mark
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