High End Tuning Question
#1
Thread Starter
My Feedback: (17)
Join Date: Nov 2002
Location: Goodyear, AZ
Posts: 1,427
Likes: 0
Received 0 Likes
on
0 Posts
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?
#7
Senior Member
My Feedback: (48)
Join Date: Dec 2003
Location: Millington,
MI
Posts: 990
Likes: 0
Received 0 Likes
on
0 Posts
RE: High End Tuning Question
ORIGINAL: dick Hanson
Really?
why?
ORIGINAL: AirWizard
I think the reason you back it off is that in the air the engine will go leaner.
I think the reason you back it off is that in the air the engine will go leaner.
why?
#9
Senior Member
My Feedback: (3)
Join Date: Apr 2004
Location: Coffeyville,
KS
Posts: 1,228
Likes: 0
Received 0 Likes
on
0 Posts
RE: High End Tuning Question
ORIGINAL: dick Hanson
Really?
why?
ORIGINAL: AirWizard
I think the reason you back it off is that in the air the engine will go leaner.
I think the reason you back it off is that in the air the engine will go leaner.
why?
#13
Senior Member
My Feedback: (1)
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.
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.
#14
Senior Member
My Feedback: (1)
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.
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.
#15
Junior Member
Join Date: Oct 2003
Location: prattville,
AL
Posts: 5
Likes: 0
Received 0 Likes
on
0 Posts
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.
#16
My Feedback: (41)
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?
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?
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.
#20
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
Karol
#22
Senior Member
Join Date: Jun 2002
Location: , IN
Posts: 777
Likes: 0
Received 0 Likes
on
0 Posts
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??