Does it make a difference which direction the spray bar sprays as long as it's pointed downward into the intake toward the shaft?
Louis Keller,Jr.
angle of needle valve spray bar?
Stuka Stunt Main Forum · 14 of 14 known posts recovered
>Does it make a difference which direction the spray bar
>sprays as long as it's pointed downward into the intake toward
>the shaft?
I believe that the hole should be 'just out of view.'
That is the area of highest velocity and lowest pressure without suffering any ram air effects.
Pointing straight down the throat of the venturi will place the hole in an area of turbulence and give unpredictable results.
Cheers.
>sprays as long as it's pointed downward into the intake toward
>the shaft?
I believe that the hole should be 'just out of view.'
That is the area of highest velocity and lowest pressure without suffering any ram air effects.
Pointing straight down the throat of the venturi will place the hole in an area of turbulence and give unpredictable results.
Cheers.
Still learning after 50 years.
>Does it make a difference which direction the spray bar
>sprays as long as it's pointed downward into the intake toward
>the shaft?
In theory, maybe. Some even claim you can adjust it the same way you would change tank height. I have tried different ways and found absolutely no difference in engine run whether it was angled down or straight down. So I just set them straight down and move on.
Try it and see if you can detect a difference. That is something easily done and doesn't cost a thing.
>sprays as long as it's pointed downward into the intake toward
>the shaft?
In theory, maybe. Some even claim you can adjust it the same way you would change tank height. I have tried different ways and found absolutely no difference in engine run whether it was angled down or straight down. So I just set them straight down and move on.
Try it and see if you can detect a difference. That is something easily done and doesn't cost a thing.
Leonard Neumann
Indianapolis, Indiana, USA
Indianapolis, Indiana, USA
>>Does it make a difference which direction the spray bar
>>sprays as long as it's pointed downward into the intake
>toward
>>the shaft?
>
>In theory, maybe. Some even claim you can adjust it the same
>way you would change tank height. I have tried different ways
>and found absolutely no difference in engine run whether it
>was angled down or straight down. So I just set them straight
>down and move on.
>
>Try it and see if you can detect a difference. That is
>something easily done and doesn't cost a thing.
I've istalled my needle spray bar hole, in my Fox .35 Stunt motors, at numerous angles 
and found that, what works best for my engines, is to aim the needle spray bar hole, "down", and at the same angle, as the throat of the venturi, "not at the verticle or horizontal" 
In my motor test's 
, I found that my "Fox .35 Stunt" motors would run poorly, if the needle spray bar hole, was installed in any angle, where I could "clearly" see the needle spray bar hole 
All my Fox .35 Stunt spray bars have a single hole. 
>>sprays as long as it's pointed downward into the intake
>toward
>>the shaft?
>
>In theory, maybe. Some even claim you can adjust it the same
>way you would change tank height. I have tried different ways
>and found absolutely no difference in engine run whether it
>was angled down or straight down. So I just set them straight
>down and move on.
>
>Try it and see if you can detect a difference. That is
>something easily done and doesn't cost a thing.
I've istalled my needle spray bar hole, in my Fox .35 Stunt motors, at numerous angles and found that, what works best for my engines, is to aim the needle spray bar hole, "down", and at the same angle, as the throat of the venturi, "not at the verticle or horizontal" In my motor test's , I found that my "Fox .35 Stunt" motors would run poorly, if the needle spray bar hole, was installed in any angle, where I could "clearly" see the needle spray bar hole All my Fox .35 Stunt spray bars have a single hole. Peekaboo
Jim Thomerson · Oct 10, 2011 09:21 AM
#4 sourceOn the other hand, my Fox 35 ran fine. When the run was over I looked in the venturi and the spraybar hole was looking back at me. Yes, I did rotate it back out of sight and tighten up the spraybar.
>On the other hand, my Fox 35 ran fine. When the run was over
>I looked in the venturi and the spraybar hole was looking back
>at me. Yes, I did rotate it back out of sight and tighten up
>the spraybar.
Were you using the stock Fox needle? If so, it has two holes opposite one another. Might explain a bit why it worked that way.
>I looked in the venturi and the spraybar hole was looking back
>at me. Yes, I did rotate it back out of sight and tighten up
>the spraybar.
Were you using the stock Fox needle? If so, it has two holes opposite one another. Might explain a bit why it worked that way.
Leonard Neumann
Indianapolis, Indiana, USA
Indianapolis, Indiana, USA
Still learning after 50 years.
Jim Thomerson · Oct 10, 2011 08:03 PM
#7 sourceST NVA, single hole.
Anachronis · Oct 10, 2011 11:52 PM
#8 sourceNZMAA sites got something there in a comp report about the position for a LA 25 for restarts , raceing , back or fwd , not both ,
Wrong way , it wont . They say . or is it excuses excuses
Wrong way , it wont . They say . or is it excuses excuses
ANACHRONOUS
This quote sums it up VERY well -
"Using a manometer an an appropriate source of moving air, you will find that when rotating the spray bar in the venturi that draw is essentially constant when the hole is out of sight, and will bump up by about 15% when it is positioned in the exact right spot."
From -
http://controlline.org.uk/phpBB2/viewtopic.php?t=5236&highlight=
(second last post on page one.)
Cheers.
"Using a manometer an an appropriate source of moving air, you will find that when rotating the spray bar in the venturi that draw is essentially constant when the hole is out of sight, and will bump up by about 15% when it is positioned in the exact right spot."
From -
http://controlline.org.uk/phpBB2/viewtopic.php?t=5236&highlight=
(second last post on page one.)
Cheers.
Still learning after 50 years.
>This quote sums it up VERY well -
>
> "Using a manometer an an appropriate source of moving
>air, you will find that when rotating the spray bar in the
>venturi that draw is essentially constant when the hole is out
>of sight, and will bump up by about 15% when it is positioned
>in the exact right spot."
>
>From -
>
>http://controlline.org.uk/phpBB2/viewtopic.php?t=5236&highlight=
>(second last post on page one.)
>
>Cheers.
>
That post was By Bill Lee.
BILL!
How many inches of water column will be in the ball park flow range?
Should be able to reduce flow on the old flow bench enough if I have a
working range.
(can convert mercury to water)
Dont think my manometer for checking draw/pressure is small or accurate
enough/wide scale enough.
alcohol might be light enough and make it usable?
>
> "Using a manometer an an appropriate source of moving
>air, you will find that when rotating the spray bar in the
>venturi that draw is essentially constant when the hole is out
>of sight, and will bump up by about 15% when it is positioned
>in the exact right spot."
>
>From -
>
>http://controlline.org.uk/phpBB2/viewtopic.php?t=5236&highlight=
>(second last post on page one.)
>
>Cheers.
>
That post was By Bill Lee.
BILL!
How many inches of water column will be in the ball park flow range?
Should be able to reduce flow on the old flow bench enough if I have a
working range.
(can convert mercury to water)
Dont think my manometer for checking draw/pressure is small or accurate
enough/wide scale enough.
alcohol might be light enough and make it usable?
BillLee20018 · Oct 14, 2011 11:36 PM
#11 sourceDavid, that experiment was done many, many years ago, like back in the 70's! But others have replicated it. I often have a hard time remembering what happened yesterday! 
The manometer I used was a piece of large plastic fuel line. Probably used 50" or there abouts formed in a U and about half full of water. Simply mounted it to the wall next to the workbench. The U was about 2' top to bottom.
One end was connected to the spray bar with another piece of fuel line, the other end open to air.
The venturi I was testing was the CL venturi off a K&B 3.5, and the needle valve assemble was a K&B as I recall. The NV body was lightly tightened in the venturi, the needle valve run in a ways, probably about where the engine would want it.
The air source was a shop vac, but only a part of it's inlet since too much wouldn't draw through the small (relative) diameter venturi. Needed to play with this until I got the manometer working within the range it had.
Started testing by seeing what the manometer did with a constant airflow through the venturi as I rotated the needle valve body. The results were as I posted on the Barton forum: the draw as measured by the manometer was the same anywhere the needle valve hole was out of sight until you found that one small area where the draw would suddenly jump upward by about 12%-15%. The range where the "sweet spot" occurred was only a couple of degrees wide, and I doubt you would ever reliably hit it by eye.
BTW, I used that venturi (.340 diameter with full spray bar as I recall) in a K&B 40S, a serious racing motor, and it would needle like a stunt motor with superb fuel draw.
Bill
The manometer I used was a piece of large plastic fuel line. Probably used 50" or there abouts formed in a U and about half full of water. Simply mounted it to the wall next to the workbench. The U was about 2' top to bottom.
One end was connected to the spray bar with another piece of fuel line, the other end open to air.
The venturi I was testing was the CL venturi off a K&B 3.5, and the needle valve assemble was a K&B as I recall. The NV body was lightly tightened in the venturi, the needle valve run in a ways, probably about where the engine would want it.
The air source was a shop vac, but only a part of it's inlet since too much wouldn't draw through the small (relative) diameter venturi. Needed to play with this until I got the manometer working within the range it had.
Started testing by seeing what the manometer did with a constant airflow through the venturi as I rotated the needle valve body. The results were as I posted on the Barton forum: the draw as measured by the manometer was the same anywhere the needle valve hole was out of sight until you found that one small area where the draw would suddenly jump upward by about 12%-15%. The range where the "sweet spot" occurred was only a couple of degrees wide, and I doubt you would ever reliably hit it by eye.
BTW, I used that venturi (.340 diameter with full spray bar as I recall) in a K&B 40S, a serious racing motor, and it would needle like a stunt motor with superb fuel draw.
Bill
Bill
All this got me to thinking....or something.
Should be able to:
Set needle valve to let say max RPM then shut engine off.
barely loosen spay bar nut, restart engine.
rotate assembly until richest mixture is obtained, note or mark position
and shut engine off.
tighten nut in noted or marked (riches) position.
Think that would work?
P.s.(ref earlier post)
A big shop vac will flow enough to do adequate flow work on Chev Big Block heads.
Still looking for a 6.5 piston/cylinder!!
All this got me to thinking....or something.
Should be able to:
Set needle valve to let say max RPM then shut engine off.
barely loosen spay bar nut, restart engine.
rotate assembly until richest mixture is obtained, note or mark position
and shut engine off.
tighten nut in noted or marked (riches) position.
Think that would work?
P.s.(ref earlier post)
A big shop vac will flow enough to do adequate flow work on Chev Big Block heads.
Still looking for a 6.5 piston/cylinder!!
Jim Thomerson · Oct 20, 2011 06:55 PM
#13 sourceModel Airplane News used to include a fuel draw figure in its engine reviews; how low the fuel tank could be below the spraybar and the engine still suck fuel and run. As I recall, 12 inches was thought to be pretty good. So maybe a suction (negative pressure) of around 0.5 psi