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Old 11-14-2017, 01:00 PM   #1
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Default Horizontal Sump

Of those with a horizontal sump, how many of you have a sniffle valve installed at the bottom of your sump? Most mooneys have them, but it doesn't appear to be standard equipment on a Pitts.


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Old 11-14-2017, 01:54 PM   #2
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I do not have one, but Don at AFP did recommend that I install one.


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Old 11-14-2017, 02:43 PM   #3
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Fuel injection usually have sniffle valves. Pooled fuel can usually fall out of carb engines.
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Old 11-14-2017, 03:01 PM   #4
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I had a neighbor with an angled valve io360 in a velocity. He could not crank it and I noticed he did not have a sniffle valve. I removed the plug and approximately one pint of gas ran out on the floor. It was severely flooded. I have one in mine and it occasionally drips. If you over prime there is no where for the fuel to go except up the intakes,
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Old 11-14-2017, 03:28 PM   #5
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I don't have one and this reminded me that I should........
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Old 11-14-2017, 03:48 PM   #6
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I figure if I get pooled up fuel, I'll just roll inverted to clear it out.
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Old 11-14-2017, 03:51 PM   #7
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Hard to do on the ground Cameron. The Extra I flew had a big problem with that -- you could not keep the engine running after a hot start without leaning the mixture way out. So that meant taxiing with a very lean setting and remembering not to take off without getting it to run in the full rich position. I was told the port in the sump was in the wrong place to allow the fuel to drain when you were three point.
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Old 11-14-2017, 04:07 PM   #8
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The factory Pitts does not use a sniffle valve. Probably for the 3 point issue mentioned above. My mechanic suggested adding one, but I don't have problems with starting. I do NOT flood the engine. The flight manual procedure works very well both cold and hot. And hot means run within the last 4 hours for my S-2A.

Best of luck,

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Old 11-14-2017, 05:30 PM   #9
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Thanks for the responses. My S2A didn’t have one, but I just finished rebuilding my engine and thought about adding one. It started well, but wanted to conduct a survey. The port is more forward and would only be beneficial if severely flooded.
4954EF63-B8E9-4426-8D70-FA37454599AC.jpg   A85C6DFF-197D-4AFD-BFA4-5D2F19FDF61B.jpg   6A396AF0-F62D-4FF9-BC2B-7C360DCB945C.jpg  

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Old 11-14-2017, 06:10 PM   #10
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Ben, love the color. It matches the yellow on my GO-300 in my C-175!
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Old 11-16-2017, 03:55 AM   #11
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Wow nice work Ben!
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Old 11-16-2017, 12:28 PM   #12
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That is beautiful! (What the hell is a sniffle valve?)
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Old 11-16-2017, 01:14 PM   #13
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Sniffle valve - If you look at the middle picture of post #9, below the hose that crosses the sump, you will see a silver colored plug. When the engine is installed in a Mooney that plug is replaced with a sniffle valve.

The function of a sniffle valve is to allow a leak when there is no negative pressure in the sump. So if you over-prime the engine as you attempt a start, the excess fuel drains away onto the nose gear and the ground. This only works if the engine sits level with the airplane parked. The location in the middle of the sump does not work so well if the engine is installed in a tailwheel airplane. With the engine installed so that it sits tilted nose high, a significant amount of fuel can still puddle in the aft end of the sump's intake plenum before the sniffle valve can allow some to drain.

Hope this explanation makes sense.

Wes
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Old 11-16-2017, 01:25 PM   #14
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It's like a check valve but in reverse. There is a small flat piece of phenolic sheet that's captured in a small housing that screws into the intake area. If you over prime the engine supposedly the sniffle valve allows leakage of the accumulated fuel. When the engine starts, the small phenolic ''valve'' is sucked into position by vacuum and seals off the opening.

Took one apart once and if anyone remembers the reed valve in the old Cox .049 model airplane engine this setup will look vaguely familiar. It's pretty easy to flood the horizontal intake engines so this form of a controlled leak is supposed to drain the excess fuel overboard and out of the cowl via a small rubber tube attached to the valve.

Apparently I was typing my response when Wes was doing the same. I would delete my post but the ''delete'' function has been, ah..., well, deleted?!


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