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Sniffle valve

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Mark Phillips in TN

Joined: 10 Jan 2006
Posts: 431
Location: Columbia, TN

Posted: Mon May 21, 2007 3:04 pm Post subject: Sniffle valve

I am installing a Lycoming sniffle valve (included in Vans FWF kit) to an Aerosport IO-360 and would like to confirm its inteded operation.  I "think" it is basically a check valve that should open when manifold pressure is equal to atmospheric (engine not running) to drain any fuel pooled in the sump.  Engine running, it should close when manifold pressure drops.  The valve I have flows freely when blowing into the sump side, but still passes a bit of air when blown into from the tube side, which I surmise would constitute a small vacuum leak and possible leaner than normal operation.  

  

 Is this normal?

  

 Thanks-

 Mark



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glcasey(at)adelphia.net
Guest

Posted: Tue May 22, 2007 4:15 am Post subject: Sniffle valve

I assume most Lycoming installations (at least the 3 that I have  

owned) just use a simple drain, so there is a "leak" the size of the  

tube when the engine is running.  The idle speed and mixture  

adjustments compensate, so no one seems to worry.  A sniffle valve  

would presumably reduce that leak, but apparently isn't necessary.

Gary Casey



 	  Quote: 	
		  

 I am installing a Lycoming sniffle valve (included in Vans FWF kit)  

 to an

 Aerosport IO-360 and would like to confirm its inteded operation.   

 I "think" it



 is basically a check valve that should open when manifold pressure  

 is equal to



 atmospheric (engine not running) to drain any fuel pooled in the  

 sump.  Engine



 running, it should close when manifold pressure drops.  The valve I  

 have

 flows freely when blowing into the sump side, but still passes a  

 bit of air when



 blown into from the tube side, which I surmise would constitute a  

 small vacuum



 leak and possible leaner than normal operation.



 Is this normal?



 Thanks-

 Mark

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apilot2(at)gmail.com
Guest

Posted: Tue May 22, 2007 4:29 am Post subject: Sniffle valve

The engines I'm familiar with all call for a sniffle valve, that looks

like a standard AN 90 degree fitting. I don't know how well it is

supposed to seal after fuel and gunk have drained through it for a few

years.



On 5/22/07, Gary Casey <glcasey(at)adelphia.net> wrote:

 	  Quote: 	
		   



 I assume most Lycoming installations (at least the 3 that I have

 owned) just use a simple drain, so there is a "leak" the size of the

 tube when the engine is running.  The idle speed and mixture

 adjustments compensate, so no one seems to worry.  A sniffle valve

 would presumably reduce that leak, but apparently isn't necessary.

 Gary Casey



 >

 > I am installing a Lycoming sniffle valve (included in Vans FWF kit)

 > to an

 > Aerosport IO-360 and would like to confirm its inteded operation.

 > I "think" it

 >

 > is basically a check valve that should open when manifold pressure

 > is equal to

 >

 > atmospheric (engine not running) to drain any fuel pooled in the

 > sump.  Engine

 >

 > running, it should close when manifold pressure drops.  The valve I

 > have

 > flows freely when blowing into the sump side, but still passes a

 > bit of air when

 >

 > blown into from the tube side, which I surmise would constitute a

 > small vacuum

 >

 > leak and possible leaner than normal operation.

 >

 > Is this normal?

 >

 > Thanks-

 > Mark

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MONTY(at)bpaengines.com
Guest

Posted: Tue May 22, 2007 7:23 am Post subject: Sniffle valve

If you have a small leak at the “ sniffle “ valve it will only effect you at idle and can be compensated with idle mixture adjustment.  At WOT the engine doesn’t care as long as the leak is small.  A big hole is another story.  

   

Monty Barrett  

BPE, Inc.  

   

--

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Mark Phillips in TN

Joined: 10 Jan 2006
Posts: 431
Location: Columbia, TN

Posted: Tue May 22, 2007 10:54 pm Post subject: Sniffle valve

In a message dated 5/22/2007 10:25:10 AM Central Daylight Time, 

MONTY(at)bpaengines.com writes:



If you have a small leak at the “ sniffle “ valve it will only effect you at 

idle and can be compensated with idle mixture adjustment.  At WOT the engine 

doesn’t care as long as the leak is small.  A big hole is another story.



 	  Quote: 	
		  >>>

 
	


Thanks to all respondents- good discussion.  Primary concern was a defective 

part, but it don't sound like a biggie- I'm puttin' the sucker in since it's 

paid for and shouldn't make the plane fall out of the sky!   

 

Mark do not archive



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