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10-04-2010, 09:33 PM
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Join Date: Oct 2009
Location: Uberaba, MG, Brazil
Posts: 122
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Leaning LOP
Hi folks
I fly a RV-10 with IO540 and dynon skyview and I notice that cylinder number 1 is the first one to peak every time. However, as I continue leaning I notice its temperature continues to fall and suddenlly its trend inverts and it starts to raise as others cylinders are reaching peak or have already reached peak and are getting further down on lean side. Last flight this first cylinder peaked and as I continue leaning and after decreasing about 15 degrees on lean side, the gas temp on the cylinder started to raise, even though other were decreasing on lean side, and even reached yellow line as other cylinder temp were going down. Resuming, this cylinder is the first to peak, temp goes down and then up. What is happening? Any ideas?
Thank you
Moura
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10-05-2010, 05:25 AM
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Join Date: Jan 2005
Location: Louisville, Ga
Posts: 7,840
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Bad probes, maybe?
Hi Moura,
My -10's # 1 cylinder recently started intermittently showing 1650, while the others were around 1280-1300. After I started leaning, its temperature went down close to the others, then occasionally jumped to 1650 or so. We decided to change the probe and see if that is the problem. The engine only has 350 hours on it.
Best,
__________________
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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10-05-2010, 05:51 AM
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Join Date: Oct 2009
Location: Uberaba, MG, Brazil
Posts: 122
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Pierre, it does not seem like a bad probe as the temps are all similar and this only happens when I pull the misture. Thanks
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10-05-2010, 06:52 AM
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Join Date: Sep 2005
Location: Maple Grove, MN
Posts: 2,334
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It is normal to see the rise again, although at only 15 LOP, I'm not sure. I understand it is called lean mis-fire, where the cylinder becomes so lean that it doesn't burn properly. On mine, it takes something like 100 LOP to see it. However, I run dual EI's on mine, if you are running straight mags, it might occur much sooner. I know when I had the Lasar system, and could revert to straight mags in flight, I could not go much lean of peak before roughness. EI really shines LOP.
Run the fuel balance and see where things are - that cylinder may just need a little larger injector.
Here you can see a couple cylinders started to trend upward:

__________________
Alex Peterson
RV6A N66AP 1700+ hours
KADC, Wadena, MN
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10-05-2010, 07:15 AM
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Join Date: Feb 2005
Location: Chesterfield, Missouri
Posts: 4,514
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Alex,
I think the IAS plot is lying to you.
There's no way IAS will increase when LOP, the engine is producing less power.
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10-05-2010, 07:23 AM
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Join Date: Jan 2006
Location: New Smyrna Beach, FL
Posts: 1,339
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Quote:
Originally Posted by David-aviator
Alex,
I think the IAS plot is lying to you.
There's no way IAS will increase when LOP, the engine is producing less power.
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It looks to me like IAS is going down after EGT peaks, as it should.
__________________
David Maib
RV-10 N380DM
New Smyrna Beach, FL
VAF Paid 1/21/2020
"In '69 I was 21, and I called the road my own"
Jackson Browne
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10-05-2010, 07:26 AM
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Join Date: Feb 2005
Location: Chesterfield, Missouri
Posts: 4,514
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Quote:
Originally Posted by dmaib
It looks to me like IAS is going down after EGT peaks, as it should.
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You are so correct!
__________________
RV-12 Build Helper
RV-7A...Sold #70374
The RV-8...Sold #83261
I'm in, dues paid 2019 This place is worth it!
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10-05-2010, 07:50 AM
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Join Date: Oct 2009
Location: Uberaba, MG, Brazil
Posts: 122
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As for the temp goling down and then back up, I don?t see it in the graph. Is it normal to go down and them back up?
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10-05-2010, 08:36 AM
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Join Date: Sep 2007
Location: pittsburgh pa
Posts: 533
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I see the same thing
And am very curious to hear possible explanations. IO-360, 1 mag, 1 LSE, AFP injection with good injector balance. Typical "Economy Cruise" at WOT at 2200 or 2400 RPM as necessary to get % power to 65% or below.
As I lean, I see an orderly and predictable decrease in EGT past peak to about 25 - 65 degrees LOP (typically in the 1450 degree EGT range). Then I begin to see a fairly abrupt rise (typically just before roughness occurs).
Fearing the worst, I just don't go there (into the increasing EGT range).
The band of confortable LOP EGT temps seems to be dependent on % power. The lower the precent power the more degrees beyond peak I can go before seeing the rise and the less abrupt the rise seems to be.
I have not studied each and every cylinder EGT to see if they are all in concert during this occurrence. When I see one rise, I richen slightly into the comfortable range and go with it. In this comfort range, I see all of the expected benefits of LOP - lower CHT's, lower fuel burns (about 7.5 gph typical) and slightly lower A/S (drops 5 - 7 knots).
Anybody with insights into this??? Thanks
__________________
Gary Reed
RV-6 IO-360
WW 200 RV now an Al Hartzell for improved CG
Last edited by gereed75 : 10-05-2010 at 08:43 AM.
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10-05-2010, 08:42 AM
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Join Date: Feb 2005
Location: Chesterfield, Missouri
Posts: 4,514
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Quote:
Originally Posted by Moura
As for the temp goling down and then back up, I don?t see it in the graph. Is it normal to go down and them back up?
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Look at #4, that's what Alex was referring to. EGT levels off, starts to go down and then goes up some more. #1 #2 #3 are smooth curves, #4 is not.
I see it sometimes with #1, it is an aberration of a sort. 
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RV-12 Build Helper
RV-7A...Sold #70374
The RV-8...Sold #83261
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