|
-
POSTING RULES

-
Donate yearly (please).
-
Advertise in here!
-
Today's Posts
|
Insert Pics
|

10-06-2010, 12:44 PM
|
|
|
|
Join Date: Jan 2005
Location: Shorewood, WI (Milwaukee area)
Posts: 1,066
|
|
LOP
Thanks for posting that reply; I never knew about the "second peak."
__________________
Bill Dicus
Shorewood (Milwaukee) Wisconsin
RV-8 N9669D Flying 12/4/14!
Flying Pitts S-2A, Piper Lance
|

10-06-2010, 01:35 PM
|
 |
|
|
Join Date: Sep 2005
Location: Maple Grove, MN
Posts: 2,334
|
|
Quote:
Originally Posted by erich weaver
Forgive me, as perhaps this is detracting from your ultimate question, but the above was not my recollection, so I took a minute to check, and have posted my findings below. In his Pelican's Perch #18 article, "Mixture Magic", available on the Avweb website, he says:
"Now suppose you lean by the classic advice "lean 'till roughness occurs, then enrich just enough to restore smoothness." No one wants to run a rough engine, so this is good advice. A rough engine causes metal fatigue, pilot fatigue, sterility, baldness, imp ?, but, I digress. I think we can all agree that vibration is a bad thing, all around. What's causing that vibration? Aha, I see that hand in back there in the audience. What's that you say? "Lean misfire?"
Sorry Charlie, no tuna. There's essentially no such thing as "lean misfire." It's probably a term some tech rep made up because he didn't know the right answer. A properly set up engine will tolerate leaning and remain smooth right down to that 30% power range (see combustion chart), at which point it just quits cold. There's no reason to shake, at all. Now that said, the real world is not perfect, and even well-set-up engines will show a just a tiny bit of roughness when leaned to the extreme. What does happen to cause that roughness is that the first cylinder to peak and start down on the lean side will produce less power than the others, and unequal power from one cylinder (or more) will cause enough vibration to be obvious. So you enrich until the vibration goes away, restoring that one cylinder (or more) to approximately the same actual power as the others. That gets them all up on the "sort of flat" part of the power curve..."
best regards
erich
|
You are correct. Somewhere I saw (I thought on Deakin's articles), a graph just like the one I put up earlier, with an arrow pointing to the upturn in egt at very lean conditions, using the word "lean misfire". Must not have been Deakin, but I'm not sure who else it would have been.
Automotive error codes use the term, and I'm not sure what they are looking at or referring to either.
__________________
Alex Peterson
RV6A N66AP 1700+ hours
KADC, Wadena, MN
|

10-07-2010, 10:24 AM
|
 |
|
|
Join Date: Aug 2006
Location: Taylor Texas
Posts: 811
|
|
EGT increase @ extreme LOP?
Well, if that cyl peaks 1st, then it will also 'flame out' 1st. One thing that can increase EGT is burning fuel in the exh pipe, which could be happening due to the slower combustion of the VERY lean mixture in that cylinder.
That being said, I have never heard of a second peak either, but if it happend at extremely lean mixtures, the above explanation is plausible.
Balance your injectors ASAP, tho I doubt you would cause any damage to continue on. Don Rivera at AFP will help you thru the tuning process.
Carry on!
Mark
|

10-07-2010, 03:37 PM
|
|
|
|
Join Date: Oct 2009
Location: Uberaba, MG, Brazil
Posts: 122
|
|
I emailed Don at airflow and below is his response:
"What's happening is that as you lean the mixture the time to burn the mixture in the cylinder takes longer. Since the spark event starts at the same crank angle the leaner mixture is still burning after the exhaust valve starts to open. This is pretty normal for Lycoming engines.
If you richened that cylinder up it would peak closer the other cylinders."
|

10-07-2010, 05:47 PM
|
|
|
|
Join Date: Sep 2007
Location: pittsburgh pa
Posts: 533
|
|
Thanks guys
Mystery solved. Thanks for tracking that one down. Always ask the experts!!
Fly on!!
__________________
Gary Reed
RV-6 IO-360
WW 200 RV now an Al Hartzell for improved CG
|

10-08-2010, 06:13 AM
|
 |
|
|
Join Date: Jan 2005
Location: Louisville, Ga
Posts: 7,840
|
|
Yeah, the guys at AFP are great to deal with..
...and I spoke with Kyle, since Don was preoccupied, for a new set of injector inserts...025" for starters. My airplane is in for annual/condition inspection and totally naked  , so it's a good time to start balancing the cylinders.
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!
|

10-09-2010, 09:21 PM
|
|
|
|
Join Date: Oct 2009
Location: Uberaba, MG, Brazil
Posts: 122
|
|
You bet Pierre, they sure are... and indeed so are you guys who participate in such a active manner in this forum!!! Thank you all!!!
Moura
|

10-10-2010, 07:38 AM
|
 |
|
|
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,687
|
|
Quote:
Originally Posted by pierre smith
...and I spoke with Kyle, since Don was preoccupied, for a new set of injector inserts...025" for starters. My airplane is in for annual/condition inspection and totally naked  , so it's a good time to start balancing the cylinders.
Best,
|
Pierre,
I also switched to .025 from the "std" .028 then tuned from there. Ended up with 2ea .025, an .026, and a .0265, peaks are now within .2 gph
Walt
__________________
Walt Aronow, DFW, TX (52F)
EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
All times are GMT -6. The time now is 06:52 AM.
|