Notices
Gas Engines Questions or comments about gas engines can be posted here

High End Tuning Question

Old 07-27-2007, 09:12 PM
  #1  
chuck l
Thread Starter
My Feedback: (17)
 
Join Date: Nov 2002
Location: Goodyear, AZ
Posts: 1,427
Likes: 0
Received 0 Likes on 0 Posts
Default High End Tuning Question

There are frequent references to tuning the high speed needle for max rpm, then richening it for a 200rpm drop. Can some one explain the reason/theory for doing this? Can you really tell any difference when flying the plane?
Old 07-27-2007, 09:35 PM
  #2  
AirWizard
Senior Member
My Feedback: (3)
 
AirWizard's Avatar
 
Join Date: Apr 2004
Location: Coffeyville, KS
Posts: 1,228
Likes: 0
Received 0 Likes on 0 Posts
Default RE: High End Tuning Question

I think the reason you back it off is that in the air the engine will go leaner.
Old 07-27-2007, 09:43 PM
  #3  
bubbagates
My Feedback: (32)
 
bubbagates's Avatar
 
Join Date: May 2004
Location: Elizabethtown, PA
Posts: 8,635
Likes: 0
Received 1 Like on 1 Post
Default RE: High End Tuning Question

AirWizard hit it right on the head. plus in most cases you are on the high needle most of the time so you get the added benefit of a little extra cooling from the fuel/oil mix
Old 07-27-2007, 11:28 PM
  #4  
rmh
Senior Member
 
rmh's Avatar
 
Join Date: Dec 2001
Location: , UT
Posts: 12,630
Likes: 0
Received 0 Likes on 0 Posts
Default RE: High End Tuning Question


ORIGINAL: AirWizard

I think the reason you back it off is that in the air the engine will go leaner.
Really?
why?
Old 07-28-2007, 12:20 AM
  #5  
Tired Old Man
Senior Member
My Feedback: (1)
 
Join Date: Feb 2002
Location: Valley Springs, CA
Posts: 18,602
Likes: 0
Received 3 Likes on 3 Posts
Default RE: High End Tuning Question

This is going to get interesting. It's going to be so much fun I'm going to be content to simply watch. Gotta go make some popcorn[8D]
Old 07-28-2007, 12:52 AM
  #6  
JoeAirPort
My Feedback: (41)
 
JoeAirPort's Avatar
 
Join Date: Aug 2003
Location: Milwaukee, WI
Posts: 10,259
Likes: 0
Received 0 Likes on 0 Posts
Default RE: High End Tuning Question

Fuji engines rule.
Old 07-28-2007, 07:15 AM
  #7  
tande
Senior Member
My Feedback: (48)
 
Join Date: Dec 2003
Location: Millington, MI
Posts: 990
Likes: 0
Received 0 Likes on 0 Posts
Default RE: High End Tuning Question

ORIGINAL: dick Hanson


ORIGINAL: AirWizard

I think the reason you back it off is that in the air the engine will go leaner.
Really?
why?
Ya, Me Too!---Why?---
Old 07-28-2007, 07:37 AM
  #8  
mrbigg
My Feedback: (21)
 
mrbigg's Avatar
 
Join Date: Oct 2004
Location: Streator, IL
Posts: 4,780
Likes: 0
Received 1 Like on 1 Post
Default RE: High End Tuning Question


ORIGINAL: JoeAirPort

Fuji engines rule.
Right On, Jackson![sm=lol.gif]

I think people do it for some kind of half-butt "rev limiter."
Old 07-28-2007, 07:59 AM
  #9  
AirWizard
Senior Member
My Feedback: (3)
 
AirWizard's Avatar
 
Join Date: Apr 2004
Location: Coffeyville, KS
Posts: 1,228
Likes: 0
Received 0 Likes on 0 Posts
Default RE: High End Tuning Question


ORIGINAL: dick Hanson


ORIGINAL: AirWizard

I think the reason you back it off is that in the air the engine will go leaner.
Really?
why?
Your the engine master.....does it go leaner in the air?
Old 07-28-2007, 11:45 AM
  #10  
Tired Old Man
Senior Member
My Feedback: (1)
 
Join Date: Feb 2002
Location: Valley Springs, CA
Posts: 18,602
Likes: 0
Received 3 Likes on 3 Posts
Default RE: High End Tuning Question

No, but that's all I'm gonna say
Old 07-28-2007, 02:02 PM
  #11  
glover1482
Senior Member
 
glover1482's Avatar
 
Join Date: Nov 2005
Location: Salem, OR
Posts: 282
Likes: 0
Received 0 Likes on 0 Posts
Default RE: High End Tuning Question

I just love constructive posts... RCU rocks!

Fly safe, Glover
Old 07-28-2007, 03:23 PM
  #12  
karolh
 
Join Date: May 2002
Location: Mandeville, JAMAICA
Posts: 6,718
Likes: 0
Received 18 Likes on 17 Posts
Default RE: High End Tuning Question

This is just not fair. Someone please come to the rescue and clear up this mystery. Who me, no way

Karol
Old 07-28-2007, 04:04 PM
  #13  
Tired Old Man
Senior Member
My Feedback: (1)
 
Join Date: Feb 2002
Location: Valley Springs, CA
Posts: 18,602
Likes: 0
Received 3 Likes on 3 Posts
Default RE: High End Tuning Question

In that case, I'll pose a question or three.

If you have adjusted metering needles on the ground to obtain a specific mixture, what action could change those settings when the prop is spinning in flight? Could those specific metering settings change at all? What does or can change between the prop spinning on the ground and spinning in flight? The "does" and "can" are important and often related to performance. In the specific case presented by the original question, the "does" bears more weight.

Have at it folks, you now have a lot to work with[8D] What makes this such a good question is that it presents itself so often, generally is misunderstood or answered poorly, and now there's a great opportunity for open participation in discussion and arguement. Much will be learned form the final answers, which I truly believe the participating audience will correctly answer. It may take awhile but it will be worth the ride[sm=idea.gif]

No name calling, no "stupid", "dumb", or otherwise negative affectations, and everyone starts even. I know you can do it. The winner will be everyone[sm=thumbup.gif]

Dick, Pe, just sit back and enjoy.
Old 07-28-2007, 04:37 PM
  #14  
Big_Bird
Senior Member
My Feedback: (1)
 
Big_Bird's Avatar
 
Join Date: Dec 2001
Location: Arlington, TX
Posts: 4,258
Likes: 0
Received 2 Likes on 2 Posts
Default RE: High End Tuning Question

Well, let me take a WAG.

Could it be the variations in pressure imposed on the metering (atmospheric sensing) diaphragm on the carburetor? These changes are due to air turbulence, cowl shape, air speed, attitude and probably some others that I haven't mentioned.
Old 07-28-2007, 05:27 PM
  #15  
plane fun
Junior Member
 
Join Date: Oct 2003
Location: prattville, AL
Posts: 5
Likes: 0
Received 0 Likes on 0 Posts
Default RE: High End Tuning Question

I say it is loading and unloading of the prop in flight. The 200 rpm adjustment from peak is a good safety measure for avioding a lean run. When you are setting hi-speed needle you are putting max load on the engine because airplane is not moving. This is where you would be concerned about a lean run. I would take a guess and say at straight and level flight, the engine would have the lightest loading and therefore would actually be on the rich side.
Old 07-28-2007, 06:29 PM
  #16  
JoeAirPort
My Feedback: (41)
 
JoeAirPort's Avatar
 
Join Date: Aug 2003
Location: Milwaukee, WI
Posts: 10,259
Likes: 0
Received 0 Likes on 0 Posts
Default RE: High End Tuning Question

ORIGINAL: chuck l

There are frequent references to tuning the high speed needle for max rpm, then richening it for a 200rpm drop. Can some one explain the reason/theory for doing this? Can you really tell any difference when flying the plane?
That's the glow engine method IMO. I don't do that with my gassers. What I do is lean the high needle until the engine can no longer maintain a constant RPM at full throttle. I then richen it until the RPM's stay the same (for about 5-10 seconds anyway). The thing with the "200 RPM less" method is you don't know that simply 200 RPM less than the old setting is rich enough. It might still sag in uplines. Which is how other prople set their high needles. If they sag on an upline they land and richen it. They keep doing this until it's good. Both methods work, the flying one may be a little better. The reason many of these guys in this thread are talking funny cause they're prolly burned out repeating the same thing over and over in a new thread.

I never have engine problems and my gassers pull very strong and constant verticals. I can hear a gas engine that's too lean without using a tach (on the ground). The RPM's slowly drop and it sounds "weak" or "anemic". It's not that difficult to tune actually.
Old 07-28-2007, 07:13 PM
  #17  
altavillan
Senior Member
My Feedback: (1)
 
Join Date: Oct 2004
Location: Altaville, CA
Posts: 1,416
Likes: 0
Received 0 Likes on 0 Posts
Default RE: High End Tuning Question

It's so that when you fly at night the extra fuel shoots flames out the pipes !!!!!
Old 07-28-2007, 09:49 PM
  #18  
Tired Old Man
Senior Member
My Feedback: (1)
 
Join Date: Feb 2002
Location: Valley Springs, CA
Posts: 18,602
Likes: 0
Received 3 Likes on 3 Posts
Default RE: High End Tuning Question

A little nudge to head the right direction. It doesn't "sag" on the uplines. Though it may sound that way the description is incorrect

Continue gentlemen. There's been some good starts already.
Old 07-28-2007, 10:30 PM
  #19  
JoeAirPort
My Feedback: (41)
 
JoeAirPort's Avatar
 
Join Date: Aug 2003
Location: Milwaukee, WI
Posts: 10,259
Likes: 0
Received 0 Likes on 0 Posts
Default RE: High End Tuning Question

Ahhh whatever. Not important, my engines run great.
Old 07-28-2007, 11:08 PM
  #20  
karolh
 
Join Date: May 2002
Location: Mandeville, JAMAICA
Posts: 6,718
Likes: 0
Received 18 Likes on 17 Posts
Default RE: High End Tuning Question

Here's my 2 cents. When the prop unloads during flight there will be an increased demand for fuel, so richening the mixture while the engine is not under load at WOT is a fairly safe way of ensuring it does not go too lean during flight.

Karol
Old 07-28-2007, 11:08 PM
  #21  
Tired Old Man
Senior Member
My Feedback: (1)
 
Join Date: Feb 2002
Location: Valley Springs, CA
Posts: 18,602
Likes: 0
Received 3 Likes on 3 Posts
Default RE: High End Tuning Question

Aww, come on Joe. I didn't mean to offend. Really , I didn't.
Old 07-29-2007, 06:00 AM
  #22  
eugene
Senior Member
 
Join Date: Jun 2002
Location: , IN
Posts: 777
Likes: 0
Received 0 Likes on 0 Posts
Default RE: High End Tuning Question



I have a 10yr old weedeater with a Walbro carb, much the same engine as on my GS Warbird. Ten years ago I yanked the cord and fired it up...
Ten years later I yanked the cord and fired it up. Now, when I go after the weeds, this puts a load on the engine.. sometime it's hot and humid, sometimes cool and dry... Far as I can tell, it runs just the same as ten years ago....
Now, how did those fellas know how to set that carb for my ten year run? Did they check for sag in the high weeds??
Old 07-29-2007, 07:51 AM
  #23  
mrbigg
My Feedback: (21)
 
mrbigg's Avatar
 
Join Date: Oct 2004
Location: Streator, IL
Posts: 4,780
Likes: 0
Received 1 Like on 1 Post
Default RE: High End Tuning Question

I really think that you have to know how to read sparkplugs also. After setting the needles, fly the plane and read the plugs. You can learn alot from how the plug looks. This is what we used to do back when we were racing motorcross.
Old 07-29-2007, 11:01 AM
  #24  
JoeAirPort
My Feedback: (41)
 
JoeAirPort's Avatar
 
Join Date: Aug 2003
Location: Milwaukee, WI
Posts: 10,259
Likes: 0
Received 0 Likes on 0 Posts
Default RE: High End Tuning Question


ORIGINAL: Silversurfer

Aww, come on Joe. I didn't mean to offend. Really , I didn't.
Thanks man......we're good.
Old 07-29-2007, 12:08 PM
  #25  
Jake Ruddy
Senior Member
My Feedback: (40)
 
Jake Ruddy's Avatar
 
Join Date: May 2005
Location: Bear, DE
Posts: 4,104
Likes: 0
Received 0 Likes on 0 Posts
Default RE: High End Tuning Question

How about the change in the density of the air as you go higher..

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.