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Engine basics => Engine set up tips => Topic started by: Robin_Holden on July 28, 2009, 07:39:58 AM

Title: Spray Bar : One hole OR two ....Which is Best ?
Post by: Robin_Holden on July 28, 2009, 07:39:58 AM

Greetings all again.

I'm having problems with a well made NVA which has TWO holes in the spraybar.
Testing has shown on one of my engines , it ran much smoother and was easier to set with a traditional ST NVA with a single hole.

So guys ...... Why have TWO holes please ?
And ....... Which is better ?

Much obliged ,

Robin.

Title: Re: Spray Bar : One hole OR two ....Which is Best ?
Post by: afml on July 28, 2009, 08:00:23 AM

Hi Robin,

Could you give us a little more details on the 2 hole spraybar??
Is this a Fox spraybar?
If so, how did you install it in the motor?

If you remove the spraybar from the motor, then insert a wire through the 2 holes, you will note the holes ARE NOT in the middle of the spraybar.
The spraybar should be installed so the holes are NOT seen from the top and are located in the BOTTOM half of the spraybar. Kinda hard to describe. Will post a few pics when I return. H^^

"Tight Lines!"

Wes

Title: Re: Spray Bar : One hole OR two ....Which is Best ?
Post by: Marvin Denny on July 28, 2009, 09:06:09 AM

  In my opinion, neither is "best"   either one, positioned in the venturi properly will perform the same.  The problem usually lies in the needle fit in the spray bar rather than the one or two hole configuration.  I have taken single hole spray bars, and drilled through them to give two hole types as well as enlarging the single hole.  I also have soldered shut one hole on the two hole versions .  I have not found ANY noticable difference in performance in ANY of the configurations.  I believe it is probably the Manufacturers'  perogative.  Proper positioning of the hole(s) within the venturi throat  both laterally as well as rotation positioning is more important than the number of holes within the bar itsself.

   Bigiron

Title: Re: Spray Bar : One hole OR two ....Which is Best ?
Post by: Jim Oliver on July 28, 2009, 09:52:55 AM

Marvin,

Good to "see" that you are typing again--------two hands, now???

Best Regards,
Jim

Title: Re: Spray Bar : One hole OR two ....Which is Best ?
Post by: Marvin Denny on July 28, 2009, 01:22:26 PM

Quote from: Jim Oliver on July 28, 2009, 09:52:55 AM

Marvin,

Good to "see" that you are typing again--------two hands, now???

Best Regards,
Jim

  Two fingers partially.  Hand is quite swollen today, but is slowly improving (I think)

Title: Re: Spray Bar : One hole OR two ....Which is Best ?
Post by: Robin_Holden on July 28, 2009, 01:50:27 PM

Very much obliged to all who have commented on my question.

I've taken it all on board , thanks fellas.

Robin.

Title: Re: Spray Bar : One hole OR two ....Which is Best ?
Post by: Air Ministry . on July 28, 2009, 11:34:34 PM

Some two hole ones, the holes arnt at 180 Deg. ( there say 165 ) and want to be downish rather than upish
regarding the intake flow.

Title: Re: Spray Bar : One hole OR two ....Which is Best ?
Post by: Robin_Holden on July 29, 2009, 01:35:57 AM

Quote from: afml on July 28, 2009, 08:00:23 AM

Hi Robin,

Could you give us a little more details on the 2 hole spraybar??
Is this a Fox spraybar?
If so, how did you install it in the motor?


Wes , good morning from France and please excuse the delay in replying.

It's NOT a Fox spraybar. It's a traditional Tigre 'style' NVA but sadly I can't remember where I bought them from as I have two of them. Might be RSM ?

Much obliged ,

Robin.

Title: Re: Spray Bar : One hole OR two ....Which is Best ?
Post by: Jim Thomerson on July 29, 2009, 12:35:44 PM

I flew my Fox 35.  It ran fine. Looked in the venturi and the single hole on the ST NVA was looking out at me.  Now, I wonder, does this mean the position of the hole is not important on a Fox 35, or does it mean that my Fox 35 ordinarily runs pretty crappy and I just think it is running fine? S?P