VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics


Go Back   VAF Forums > Model Specific > RV-10
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 10-21-2018, 07:41 PM
togaflyer togaflyer is offline
 
Join Date: Apr 2013
Location: Cleveland Ga
Posts: 484
Default Lean of peak operation question

I did my first LOP flight from Georgia to the Florida Keys. Four hours non stop. Just want to see if my numbers are in the ball park. So here is how she ran:

Altitude was 9,500, speed at 150 true, 9.9 GPH, 58 percent, manafold at 19.8 percent, prop at 2390, CHTs between 331 and 364, EGTs between 1325 to 1360, LOP was -43 to -64 degrees. Engine felt good.

Does this sound about right.
Reply With Quote
  #2  
Old 10-21-2018, 08:26 PM
Paddy's Avatar
Paddy Paddy is offline
 
Join Date: Jul 2008
Location: Chicago
Posts: 216
Default CHT

Mine runs much the same. I usually bring the prop back to 2300 in LOP cruise, see about the same FF (9.5 - 10gph), a little more speed at around 160ktas. The biggest difference is CHTs, I'm used to seeing around 300 - 320deg at that altitude and WOT, could just be your higher RPM, or my northern weather. What are your temps like on the ROP side?
__________________
RV-10
Flying as of 10/30/16 after 8 yrs building

Last edited by Paddy : 10-21-2018 at 08:29 PM.
Reply With Quote
  #3  
Old 10-21-2018, 08:27 PM
scsmith scsmith is offline
 
Join Date: Jan 2008
Location: Ashland, OR
Posts: 1,913
Default What engine do you have?

The fuel flow and power numbers depend on which engine you have, but no, I don't think your numbers sound right. In particular, your fuel flow is way too high to be LOP unless you have a bigger than typical engine. Or maybe you have an RV-10 with an IO-540? In that case your fuel flow seems better, but then why are you going so slow?

I have an IO-360 angle-valve engine. Here is what my numbers would look like at 9500 ft.

2400 RPM
MP= approx 21.0 -- 21.5 in hg something like that, WOT, of course.

170 kt true

Fuel flow 8.0--8.5 gph (depending on how far LOP I want to go)

CHT approx 290F
EGT approx 1275-1300F (again depending on how far LOP I want to go)

Now, two caveats:
1) Angle valve engines tend to run with cooler CHT because they put more heat load into the oil. I have a big cooler, so my oil temp would be 180F on a 'normal' day at this condition
2) EGT from one airplane to the next means almost nothing. It depends on where the probes are installed into the header pipes. What matters is where each cylinder temp is compared to its peak.
__________________
Steve Smith
Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet"
Hobbs 515 in 9 years (would have flown more this year if not for fire smoke)
also LS-6-15/18 sailplane
VAF donation Dec 2017

Last edited by scsmith : 10-21-2018 at 08:30 PM.
Reply With Quote
  #4  
Old 10-21-2018, 08:59 PM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 1,728
Default

Based on the slow TAS Id guess you were too far done the LOP curve. In short, this means at that point you might be using a little less gas but power is dropping faster than fuel burn.

For 10GPH at 9500 feet you should have been over 160kts TAS. Try 15 to 20 degrees LOP, 2400rpm, WOT.

Did you balance the injectors?

Carl
Reply With Quote
  #5  
Old 10-21-2018, 11:04 PM
Cannon Cannon is offline
 
Join Date: Dec 2013
Location: Moorpark, CA
Posts: 50
Default

You guys realize this is the RV-10 forum, right?

Pretty sure he’s running a IO-540, not a 360.

I’ll admit to thinking same thing until I saw what forum this post was in .

Chris
__________________
1976 C-185
1947 J3C-65
RV-8 project
Reply With Quote
  #6  
Old 10-21-2018, 11:26 PM
RV10inOz's Avatar
RV10inOz RV10inOz is offline
 
Join Date: May 2008
Location: Brisbane Qld. Aust.
Posts: 2,129
Default

Quote:
Originally Posted by togaflyer View Post
I did my first LOP flight from Georgia to the Florida Keys. Four hours non stop. Just want to see if my numbers are in the ball park. So here is how she ran:

Altitude was 9,500, speed at 150 true, 9.9 GPH, 58 percent, manafold at 19.8 percent, prop at 2390, CHTs between 331 and 364, EGTs between 1325 to 1360, LOP was -43 to -64 degrees. Engine felt good.

Does this sound about right.

First things first. Did you use the lena find function to work out you were 43-63dFLOP? If so you were actually much leaner than that. Long story but basically, probes, algorithms and the fact when the CHT comes down it flows more air, and you will soon find that if you find peak again from the lean side, you were leaner than you thought. Lean Find functions are great concept teaching tools, but far from perfect operationally.

9500' depending on OAT would typically be a 10.5-10.7 GPH LOP setting. I get 9.9 at 13,000'

The fact your engine felt good suggests it has good F/A ratios and the GAMI spread would be 0.5GPH or less. So be happy!

Your TAS should be more like 160-164KTAS, so try getting more like 10dF LOP at that height (from the lean side) and see how you go. If the displayed TAS is not in the 160-164 range I bet you have a static source error. Then do a GPS box test. You are probably faster than you think.
__________________
______________________________

David Brown


The two best investments you can make, by any financial test, an EMS and APS!
Reply With Quote
  #7  
Old 10-21-2018, 11:53 PM
scsmith scsmith is offline
 
Join Date: Jan 2008
Location: Ashland, OR
Posts: 1,913
Default

Quote:
Originally Posted by Cannon View Post
You guys realize this is the RV-10 forum, right?

Pretty sure hes running a IO-540, not a 360.

Ill admit to thinking same thing until I saw what forum this post was in .

Chris
Ah, yes, I see. My bad. When you look at "today's posts" it doesn't jump out at you which sub-forum it was posted under. I should have looked.

So your numbers look like they are in the ball park, except your speed. Check your static system as suggested
__________________
Steve Smith
Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet"
Hobbs 515 in 9 years (would have flown more this year if not for fire smoke)
also LS-6-15/18 sailplane
VAF donation Dec 2017
Reply With Quote
  #8  
Old 10-22-2018, 12:00 AM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 3,274
Default

Quote:
Originally Posted by RV10inOz View Post
the fact when the CHT comes down it flows more air, ...
I am curious about your thoughts on how CHT impacts air flow into a cylinder. I understand how higher CHTs will marginally increase the air temp in the cylinder and how hotter air is less dense and therefore requiring less fuel. However, I am stumped on how CHT impacts the actual flow of air into the cylnder.

Larry
__________________
N64LR
RV-6A / IO-320, Flying as of 8/2015
RV-10 in progress
Reply With Quote
  #9  
Old 10-22-2018, 12:55 AM
RV10inOz's Avatar
RV10inOz RV10inOz is offline
 
Join Date: May 2008
Location: Brisbane Qld. Aust.
Posts: 2,129
Default

The volumetric efficiency changes slightly.......much smarter folk like George Braly could give you specifics, but go try this for yourself. Find peak from the rich side at top of climb, get appropriately LOP, then after CHT settles then find peak from the lean side and set the same amount LOP. The FF will be higher every time.
__________________
______________________________

David Brown


The two best investments you can make, by any financial test, an EMS and APS!
Reply With Quote
  #10  
Old 10-22-2018, 07:02 AM
rv6ejguy's Avatar
rv6ejguy rv6ejguy is offline
 
Join Date: Mar 2005
Location: Calgary, Canada
Posts: 4,791
Default

I'd be interested in the reasons the VE changes with CHT as well.
__________________

Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW since 2003- 424.4 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm


Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 01:30 AM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.