VansAirForceForums  
Home > VansAirForceForums

-POSTING RULES
-Advertise in here!
- Today's Posts | Insert Pics

Keep VAF Going
Donate methods

Point your
camera app here
to donate fast.


Go Back   VAF Forums > Model Specific > RV-4
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #11  
Old 03-01-2021, 08:18 PM
Ironflight's Avatar
Ironflight Ironflight is offline
VAF Moderator / Line Boy
 
Join Date: Jan 2005
Location: Dayton, NV
Posts: 12,534
Default

Quote:
Originally Posted by Toobuilder View Post
That is an OWT that started back in the radial days. If Im going somewhere cross country the throttle is advanced to the stop on takeoff and not touched again until on the descent. Power is managed with RPM and mixture, just as David suggests.
We fly our fuel injected airplanes the same way - and the only difference with the carbed ones is that we pull the throttle back just a smidge to make for better atomization in the fuel/air charge due to the tilted throttle plate. But for all intents and purposes, thatís WOT as well.

Interesting results of some prop testing I have been doing regarding RPM. If you are looking for the best SPEED while the throttle is WOT, I have found that the higher you go, the more our props (both two and three blade) like 2500 rpm for attaining the best TAS. Above that, or below that, speed drops off by a few knots. AT the standard 8,000í DA that Vanís uses for airplane comparisons, the two blade BA prop tends to keep goign faster (by just a little bit) at higher RPMís until you hit redline (I have no idea what it does above that!). The three blades peak speed is still found at about 2500 RPM however.

Iím working on getting the data ready for publishing in the near future.

Paul
__________________
Paul F. Dye
Editor at Large - KITPLANES Magazine
RV-8 - N188PD - "Valkyrie"
RV-6 (By Marriage) - N164MS - "Mikey"
RV-3B - N13PL - "Tsamsiyu"
A&P, EAA Tech Counselor/Flight Advisor
Dayton Valley Airpark (A34)
http://Ironflight.com
Reply With Quote
  #12  
Old 03-01-2021, 08:33 PM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 2,887
Default

Quote:
Originally Posted by Ironflight View Post
SNIP

Interesting results of some prop testing I have been doing regarding RPM. If you are looking for the best SPEED while the throttle is WOT, I have found that the higher you go, the more our props (both two and three blade) like 2500 rpm for attaining the best TAS. SNIP
Paul
+1. Above 8Kí or so I find 2500 RPM, WOT, 10-20 degrees LOP to be the sweet spot (RV-8, IO-360-M1B, Hartzell BA prop). Typical economy cruise is 173kts TAS, 7.5 GPH. During the winter I found running at this point the CHTs are to cold - below the 350 degree target to minimize stuck valve issues. To compensate and keep CHT up 350-360 degrees I tend to run at PEAK, burning 8.5 GPH but bumping up speed to ~180kts TAS.

Carl
Reply With Quote
  #13  
Old 03-02-2021, 08:25 AM
Dayton Murdock's Avatar
Dayton Murdock Dayton Murdock is offline
 
Join Date: Jan 2005
Location: Carson City NV
Posts: 556
Default

Hi All
My current settings are:
20" MP 2360 to 2400 RPM 8.5 GPH with these settings my TAS 180kts @10.500'
__________________
Dayton Murdock
VAF#408 RV4 N359DM O360 C/S, Dual P_Mags, AFS Efis, Trutrak A/P, Leather, Electric trim and flaps, Led lights, Freeflight ADSB and it is painted Red, Flying 1105 hrs 11/28/20

Builder Log
Reply With Quote
  #14  
Old 03-02-2021, 10:32 AM
smithflys23 smithflys23 is offline
 
Join Date: Feb 2017
Location: Jupiter
Posts: 201
Default

This is an interesting thread. Iím new to CS prop operation, and I was told that the power lever, should never be forward of the prop lever. Iím learning some things after reading this thread, and the linked articles.

I understand what has been said for climb, cruise power/prop settings, but what about aerobatics? Iíve been using 26Ē mp, 2600rpm, and full rich. Any suggestions on where power and prop should be set for aerobatics from 2-3000í?
Reply With Quote
  #15  
Old 03-02-2021, 10:36 AM
Bicyclops Bicyclops is offline
 
Join Date: Oct 2012
Location: LA, California
Posts: 361
Default

Am I the only one oversquare?

Ed Holyoke

Click image for larger version

Name:	2-24-21ovrsqrs.jpg
Views:	79
Size:	224.0 KB
ID:	8965
Reply With Quote
  #16  
Old 03-02-2021, 10:51 AM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 2,887
Default

Quote:
Originally Posted by Bicyclops View Post
Am I the only one oversquare?

Ed Holyoke
I understand the lower RPM reduces engine pumping losses - so the engine is more efficient. My experience however is that the plane is slower at lower RPM for the same fuel burn. I equate this to propeller efficiency not being constant across air speed, altitude and RPM ranges.

For the Hartzell BA prop, my experience is that at altitude the prop/engine ďsystemĒ seems to like 2480-2500 RPM as an operating spot where the power put into the prop produces the most thrust (or for the system the fuel burned yields the highest MPG for a given speed). Perhaps others have different experiences.

Iíve flown behind constant speed props that take all the engine power but are not great at converting that power to thrust. Props are a blend of science and art.

Carl
Reply With Quote
  #17  
Old 03-02-2021, 11:21 AM
Bicyclops Bicyclops is offline
 
Join Date: Oct 2012
Location: LA, California
Posts: 361
Default

Quote:
Originally Posted by Carl Froehlich View Post
I understand the lower RPM reduces engine pumping losses - so the engine is more efficient. My experience however is that the plane is slower at lower RPM for the same fuel burn. I equate this to propeller efficiency not being constant across air speed, altitude and RPM ranges.

For the Hartzell BA prop, my experience is that at altitude the prop/engine ďsystemĒ seems to like 2480-2500 RPM as an operating spot where the power put into the prop produces the most thrust (or for the system the fuel burned yields the highest MPG for a given speed). Perhaps others have different experiences.

Iíve flown behind constant speed props that take all the engine power but are not great at converting that power to thrust. Props are a blend of science and art.

Carl
I can't find a screenshot, but the same day I was seeing the same airspeed, same altitude, same fuel flow, similar CHTs at 2400RPM. The only difference I could see was that I was spinning the engine faster. Perhaps the prop was slightly more efficient at that RPM and was being offset by increased pumping loss.

I rarely set cruise power for max airspeed, mostly going for LOP and CHTs under control. Mine is a Whirlwind 74RV on a 10:1 parallel valve IO-360 in an RV-6 for reference.

Ed
Reply With Quote
  #18  
Old 03-02-2021, 02:59 PM
RV10inOz's Avatar
RV10inOz RV10inOz is offline
 
Join Date: May 2008
Location: Brisbane Qld. Aust.
Posts: 2,303
Default

Quote:
During the winter I found running at this point the CHTs are to cold - below the 350 degree target to minimize stuck valve issues. To compensate and keep CHT up 350-360 degrees I tend to run at PEAK

This is how OWT's are born.

There is no logic nor science behind such a claim. I would not only suggest you just forget this and fly LOP all year round, but strongly urge you not to promote more OWT's.

My mate Mr Deakin and co, will surely be having a fit. Walters ashes will be churning in his urn too.
__________________
______________________________

David Brown

DYNON Authorised Dealer and Installer


The two best investments you can make, by any financial test, an EMS and APS!
Reply With Quote
  #19  
Old 03-02-2021, 03:05 PM
RV10inOz's Avatar
RV10inOz RV10inOz is offline
 
Join Date: May 2008
Location: Brisbane Qld. Aust.
Posts: 2,303
Default

Quote:
Originally Posted by Ironflight View Post

Interesting results of some prop testing I have been doing regarding RPM. If you are looking for the best SPEED while the throttle is WOT, I have found that the higher you go, the more our props (both two and three blade) like 2500 rpm for attaining the best TAS. Above that, or below that, speed drops off by a few knots. AT the standard 8,000í DA that Vanís uses for airplane comparisons, the two blade BA prop tends to keep goign faster (by just a little bit) at higher RPMís until you hit redline (I have no idea what it does above that!). The three blades peak speed is still found at about 2500 RPM however.

Iím working on getting the data ready for publishing in the near future.

Paul
Paul, you are not alone here. I have found that to be true also, and with the 2 blade BA props, one VAF member whose name I can't recall (RV10 owner and ag pilot from Georgia) told me in a PM once that in his racing around the countryside he found that something like 2650-2675 he gained the best from his prop.

No doubt you will be more precise in data collection.

Something I am not happy about, recently doing side by side comparison with a Whirlwind 2 blade, the other pilot who must have been cheating somehow he was 6 knots faster on GS given the same air, same everything. SO the WW guys have pulled some speed out of the -10 for their efforts.

I can't wait to see what you come up with.
__________________
______________________________

David Brown

DYNON Authorised Dealer and Installer


The two best investments you can make, by any financial test, an EMS and APS!
Reply With Quote
  #20  
Old 03-02-2021, 03:45 PM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 2,887
Default

Quote:
Originally Posted by RV10inOz View Post
This is how OWT's are born.

There is no logic nor science behind such a claim. I would not only suggest you just forget this and fly LOP all year round, but strongly urge you not to promote more OWT's.

My mate Mr Deakin and co, will surely be having a fit. Walters ashes will be churning in his urn too.
David,

Sorry, but you are dead wrong.

I suggest you watch this Mike Busch video on why valves stick. It provides clear explanation as to why we should strive to maintain CHTs between 350 and 400 degrees.

https://youtu.be/7ohsVvYbAaQ

Carl
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 04:44 PM.


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.