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I need a sniffle valve?

S

stewartb

MEMBER
…
Yes, apparently I do. Never heard of it before today. The only reason I found out was because Lycoming fills cylinders with oil to ship. Didn't know that, either. Well some of that oil found its way into the induction and fell out of an open port. I emailed Superior to find out what the plug size was and Darrell told me about the sniffle valve. Cool. Now I know. If I'd known about the oil in the cylinders I'd have made much less of a mess. Stuff you learn along the way.
 
stewartb said:
Yes, apparently I do. Never heard of it before today. The only reason I found out was because Lycoming fills cylinders with oil to ship. Didn't know that, either. Well some of that oil found its way into the induction and fell out of an open port. I emailed Superior to find out what the plug size was and Darrell told me about the sniffle valve. Cool. Now I know. If I'd known about the oil in the cylinders I'd have made much less of a mess. Stuff you learn along the way.
Click to expand...

Do you want the continental PN? I have it somewhere.
 
The LW-75444 is a sniffle valve (sometimes referred to as or considered a fuel drain valve or adapter assembly). This type of valve offers automatic drain of overflow fuel from the sump and closes when the engine is running. In this way, sniffle valves are used as a precautionary measure, a sort of insurance policy to ensure your expensive engine is not compromised.It's important to note that this valve is only necessary on horizontal induction, fuel-injected Lycoming engines; it is not compatible with vertical induction engines. For appropriate use of this item please consult with you parts catalog
 
Vacuum closes it and gravity opens it. You’ll need a drain hole in the bottom cowl or a line attached
 
What about the purge line modification (or whatever it's called) where a return line is added to prevent the typical piddling through the injectors during heat soak. To my mind that makes more sense than a hot engine dripping gas.
 
PerryB said:
What about the purge line modification (or whatever it's called) where a return line is added to prevent the typical piddling through the injectors during heat soak. To my mind that makes more sense than a hot engine dripping gas.
Click to expand...

My FI does not leak gas when it is hot. Typically just a bit of oil.

BTW - Whoever overhauled my IO-520 neglected to install the sniffle valves. After lots of chasing and troubleshooting lean idle problems I worked on another 520 and saw these installed. Installed them in my engine, and problem fixed.

Tim
 
My servo is zero leak down so a purge valve isn't used. The valve is to drain fuel that finds its way into the induction during priming. I'm not sure I'll use it. Any fuel in the manifold should evaporate with the induction air. I think. The position of the valve is right above the exhaust. No good way to route a drain line there.

Tim, how does a sniffle impact idle mixture?
 
If you must do a flood start, due to vapor lock. The sniffle valve drains off the excess fuel from the intake or induction section of the case. Same goes for unintentional flooding during starting, leaving the mixture forward and the electric fuel pump running.
 
I get that but in my induction a cup of fuel wouldn't cause any problem that I can see and should evaporate in the induction draft. I'm curious how it contributes to a lean idle but that's just curiosity.

With electronic ignition there isn't much problem with hot starts. Prime to flood and it fires right up.
 
My valve would be scary close to my exhaust. I don't see a good solution. Perhaps leaving that port plugged is the best option. I'm looking into it. Any other horizontal induction Lycoming guys have any pireps? I'm very interested in what you've done.
 
A short flexible line off the sniffer to a solid line past the exhaust. An engine normally comes from the factory with an 1/8” pipe plug where the sniffer goes. Clearing a flooded engine without a sniffer would not be easy, depending on the severity. I’d rather it be drained off than running a bunch of excess fuel through the cylinders and exhaust.
 
I'll test fit it when it arrives. I've never heard of one of these so am trying to learn all I can. I appreciate the comments.
 
Haven't seen a mention of just where the sniffle valve goes.
I've seen an IO-520 which had a drain line running from the induction cross-over up front.
It didn't appear to have a checkvalve, but I figure it had to have something-- or maybe not.
Is that where a sniffle valve would go?
I have a 180, not a 185, so I'm a lot more familiar with O470 engines than IO's.
 
My Lycoming IO-360 that came out of a Piper Arrow had an 1/8" npt plug that was cross drilled for safety wire and then a smaller 1/32" hole that intersected the safety wire hole. I have been running it that way for 160 hours now with no issues, as far as I can tell it works. I get a little blue stain sometimes on the bottom lip of the cowling that feels more like oil.

Someone probably did not want to spend the money on the sniffle valve is my guess.

It works so I am not changing it.
 
Mike says my Cub spit raw fuel out of the exhaust at startup. If my priming sent fuel through the exhaust valves it had to be sending some into the intake, too. I didn't have a sniffle on the 400. We used that port for manifold pressure.
 
Mauleguy said:
My Lycoming IO-360 that came out of a Piper Arrow had an 1/8" npt plug that was cross drilled for safety wire and then a smaller 1/32" hole that intersected the safety wire hole. I have been running it that way for 160 hours now with no issues, as far as I can tell it works. I get a little blue stain sometimes on the bottom lip of the cowling that feels more like oil.

Someone probably did not want to spend the money on the sniffle valve is my guess.

It works so I am not changing it.
Click to expand...

I've talked to guys with FI that have had servo leak down when the engine wasn't running. They described the cylinders being "full" of fuel. A sniffle with an exterior drain would be a good thing to have in that case. Even with my zero leak down servo API recommends turning the fuel off in a gravity fed system when shutting the engine down. I never did. Maybe that contributed to the raw fuel coming out of the tailpipes at startup. It's all interesting to me.

FWIW, Piper offers a 90* sniffle valve. This one will solve my exhaust clearance problem. I think. https://www.skygeek.com/piper-492-091-valve.html
 
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I ordered a Piper valve. Not from Skygeek, either. Their AK shipping rates are insane! I think the Piper valve will do nicely. I'll move MP to the forward port and now I have a 1/8" NPT plug for the crank. It all works out.
 
Well, that idea didn't work out. The 90* Piper part is way too close to the exhaust for comfort and there's no practical way to add a drain hose. After talking to Airflow Performance I have a couple of their parts on the way. A 1/8" NPT 90* fitting and their crankcase drain because it's much smaller (wrench size/diameter) than either the Lycoming or Piper sniffel valves. And theirs uses a ball bearing instead of a flapper. Gotta wonder how the flapper would last next to a screaming hot exhaust. Don tells me the sniffel is important and not running one is a bad idea. With the close clearance between sump and Vetterman exhaust the API valve appears to be the best (only?) solution. He also told me to move the MP pickup from the sump to a cylinder primer port, which is another plumbing change that makes good sense. I learn new things every day.

I'm still curious what you other horizontal induction guys have done to drain the induction. Dealing with this little detail has been a process for me. Fortunately we have good companies with good tech support to help but in my case I didn't know I needed it. Hopefully this thread helps the next guy. And if anyone needs a Lycoming or Piper sniffel? Let's make a deal! ;)
 
Stewart, where exactly does this sniffle valve go? up front where the fuel servo is? or further back on the sump somewhere? from your exhaust clearance problems it sounds like it is up front? any pictures or drawings pls?
 
For a taildragger it goes in the most aft port in the bottom of the induction plenum. It's intended to drain any accumulated fuel while parked. The valve closes with vacuum when the engine starts so having it anyplace forward won't be effective. My Superior induction has two 1/8" NPT ports on the bottom, one forward and one aft.

I'd like to hear how others have fitted a MP line to a primer port. A 90* AN fitting won't fit. A straight fitting with a 90* hose end might work, or a 45* fitting to a 45* hose end may be even better. All I know is I can't do it with parts I have. Gotta make a new hose and buy a different fitting for the primer port.
 
Pics of my induction. Photo one shows both ports with the forward one plugged. The second photo shows the aft port relationship to the exhaust and a brace that supports cables. Space is tight under this motor.

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Sent from my iPhone using SuperCub.Org mobile app
 

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The Airflow Performance induction drain is much smaller and couple to their 90* adapter it fits. Problem resolved. I'll add an aluminum tube to route drips away from the exhaust.

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Sent from my iPhone using SuperCub.Org mobile app
 

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