eliminating sniffle valve

[toomany]

has anyone eliminated the sniffle valve on the intake in a turbo mooney or other? ours is in for annual and the intake one needs replaced - we've already replaced it ($500 for a new one)ibut i'm thinking of eliminating it just out of principal alone. I understand what it does and it's supposed purpose but i've seen plenty of 6 cyl lycoming w/o one and quite honestly would rather have the fuel remain in the intake instead of dripping on the hangar floor. please don't get into how the engineers designed the engine w the valve for a reason or how important it is to retain it - i just want to know if anyone has eliminated it and if it needed any kind of field approval. thanks. 

[MB65E]

If It’s in the IPC it’s required. However, I haven’t seen mine in about 10years! 
-Matt

[201Steve]

There is a Lycoming equivalent to the mooney part that’s like 1/10th the price if I recall @M20Doc mentioning it after I bought mine

[PT20J]

29 minutes ago, 201Steve said:

There is a Lycoming equivalent to the mooney part that’s like 1/10th the price if I recall @M20Doc mentioning it after I bought mine

It won’t fit on a J because of the proximity of the muffler. I don’t know about other models. 

[N201MKTurbo]

I could make one for about $10.

[PT20J]

16 minutes ago, N201MKTurbo said:

I could make one for about $10.

So can Mooney 

[RLCarter]

Why / how are yours failing? Pretty sure the one on my 1965 E has never been replaced

[MB65E]

6 hours ago, RLCarter said:

Why / how are yours failing? Pretty sure the one on my 1965 E has never been replaced

The newer style ones have more of a diaphragm in them. Once that goes, it won’t seal with intake vacuum. 
My reasoning for removal was that on a Lycoming tail wheel setup, one inch of fuel can gather before the sniffle valves even comes into play. You’ll know you have a flooded engine way prior to the sniffle valve leaking fuel everywhere. Also keeps fuel off the ground. Also on my E the hose and sniffle dropped right on the exhaust. That was more unsafe than extra fuel in the intake I thought. The hose coming off of the valve was very close to the exhaust. The hose also “Y’d” into the fuel pump hose drain. Now I know if my fuel pump is leaking and not the sniffle. 
-Matt. 

[toomany]

thanks for the input everyone - i'm thinking ours may go missing at some point 

[201Steve]

9 hours ago, toomany said:

thanks for the input everyone - i'm thinking ours may go missing at some point 

Just remember that you’ll need to adjust your furl mixture setting on the fi servo. It creates a different air/fuel mixture with vs without the valve. 

[N201MKTurbo]

So, when you say you are going to remove the sniffle valve, what exactly do you mean? 

Are you going to replace it with a plug or a standard elbow without the check ball? 

if you plug it, you could accumulate a fair amount of fuel in the plenum after a while, especially if you do a lot of short hops. An errant backfire could start a substantial fire.

if you replace it with a standard elbow, you will have a continuous intake leak. It may affect your idle. 

I dont know why you would get rid of it. If it quits working, cleaning it will always fix it. It’s not like it will ever wear out.

The sniffle valve only has two failure modes. It won’t close, where it is the same as a standard elbow. Or it won’t open where it is the same as a plug. So what is it doing that is causing you grief.

 

[toomany]

if or when the valve were to go missing it would be replaced w a brass plug.   not concerned about backfires as i always spin the prop to get oil pressure before introducing fuel.   i wouldn't consider and elbow as that would create an intake leak under both positive and negative pressure.  the problem w a bad sniffle valve on a turbo is that you get a right side nose gear door that is fuel stained every time you fly.  sniffle valves do go bad - this is the type w the phenolic wafer between 2 lightweight springs. luckily the great guys at Henry Weber at LNS tested out a spare off of an intercooler i had, found it to be good,  and are sending the $500 unit back.

[N201MKTurbo]

The sniffle valve on both of my Mooneys was an elbow that Mooney ran an end mill down the AN side, cross drilled a hole for a roll pin, dropped in a plastic ball, then put the roll pin in to keep the ball from falling out.

I have a turbo engine. When there is negative pressure it will suck the ball in and close it off. If there is positive pressure, it must push the ball open and I lose a bit of turbo boost. It probably lowers my critical altitude by a few feet.