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  #31  
Old 01-14-2020, 11:00 AM
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rmartingt rmartingt is online now
 
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Based on the above, does anyone see a need for a sniffle valve on an EFI engine? I would expect fuel leakage to be minimal on shutdown, especially if it's done by killing the pump or ECU power.
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  #32  
Old 01-14-2020, 11:35 AM
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The risk of water ingestion remains with a horizontal induction and any fuel system choice.

As for EFI, I have seen a bent connecting rod taken from a GM 6.0L, attributed to hydraulic lock after a defective injector dumped into the cylinder. Do the currently available EFIs hold line pressure after shutdown?
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  #33  
Old 01-14-2020, 05:50 PM
vic syracuse vic syracuse is offline
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I was short on my earlier reply on this thread as I was really busy with something. Sorry.

I donít mean to sound blunt but I donít understand risking the engine and perhaps the airplane for a $100 part. We install these valves on about half of the non-builder owner airplanes that come through our shop, because they donít have one installed. A lot of gunk and nasty stuff tends to come out of the intake when the drain plug is pulled to install the sniffle valve.

Where does it all come from you ask? Well it is a combination of a lot of things. First, any rainwater that gets into the intake when it is parked will run down the intake and carry some dirt and debris with it. And that water will sit there and pool if the rain is heavy enough, and may not evaporate prior to you trying to start the engine. Meaning there is the potential for a nice big slug of water to get sucked up and potentially cause a hydraulic lock. Want to understand the potential damage of a hydraulic lock? Read my story in KP this past summer on losing the engine in my stearman which was most likely due to a past hydraulic lock. The damage may not manifest itself for a while.


Second, Fuel drains into the cylinders from the injection system after shutdown, which over time just dries up and cakes with the rest of the dirt.

Third, sometimes there is oil leakage past the intake valves into the intake tubes, which just adds to the mess.

Lastly, on a flooded engine start, the fuel pools in the intake. Run the battery down while cranking and the potential for a backfire into the intake is a very distinct possibility. I have seen more than one crinkled filter on RVíS due to this scenario. I have also seen the damage done to the intake system from a backfire.

Not trying to preach. Just trying to share from experience. I know there are some of you who say their airplane has been running for such and such hours and has no problem. Great. I am trying to share the experience from looking at over one thousand RVís now and hope it helps you with your decision making. 😀
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  #34  
Old 01-14-2020, 06:45 PM
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Quote:
Originally Posted by DanH View Post
... Do the currently available EFIs hold line pressure after shutdown?
Mine does. Not the full 45 -50 working pressure, but it will hold 15+ PSI for several days.
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  #35  
Old 01-15-2020, 05:05 AM
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Quote:
Originally Posted by vic syracuse View Post
A lot of gunk and nasty stuff tends to come out of the intake when the drain plug is pulled to install the sniffle valve.

Where does it all come from you ask? Well it is a combination of a lot of things. First, any rainwater that gets into the intake when it is parked will run down the intake and carry some dirt and debris with it. And that water will sit there and pool if the rain is heavy enough, and may not evaporate prior to you trying to start the engine.


Second, Fuel drains into the cylinders from the injection system after shutdown, which over time just dries up and cakes with the rest of the dirt.

Third, sometimes there is oil leakage past the intake valves into the intake tubes, which just adds to the mess.

😀
Vic,

If all this collected mess can gather in the sump why is the intake of the sniffle valve only 1/16 inch in diameter? It seems it would get clogged up very easily.

(BTW, I have not had any issues over 14 years and 2200+ hours without a sniffle valve but my experience does not necessarily indicate that there is no need for one. I do have a purge valve and a water drain hole and that may account for my positive experience. At any rate, I have now installed a sniffle valve and even at $120 consider it cheep insurance.)
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  #36  
Old 01-15-2020, 05:47 AM
vic syracuse vic syracuse is offline
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Quote:
Originally Posted by ronschreck View Post
Vic,

If all this collected mess can gather in the sump why is the intake of the sniffle valve only 1/16 inch in diameter? It seems it would get clogged up very easily.

(BTW, I have not had any issues over 14 years and 2200+ hours without a sniffle valve but my experience does not necessarily indicate that there is no need for one. I do have a purge valve and a water drain hole and that may account for my positive experience. At any rate, I have now installed a sniffle valve and even at $120 consider it cheep insurance.)
Most of it drains right after shutdown. Those with sniffle valves will usually see a drop or a puddle at the exit after shutdown.

Consider thisóó the plans for the FAB box which is used in vertical draft intake systems call for drain holes for the very same reasons I mentioned in my post last night. Why would we NOT have drain holes in the intake of the horizontal intake systems????

Vic
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  #37  
Old 01-15-2020, 08:32 AM
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Quote:
Originally Posted by vic syracuse View Post
Most of it drains right after shutdown. Those with sniffle valves will usually see a drop or a puddle at the exit after shutdown.
Tell us about the exit. Intake water is one thing, but I assume you don't approve of dumping priming fuel into the lower cowl.

Sometimes a sniffle drain can be tricky. Here's an example, circa 2012, my own airplane.



That's an AFP sniffle coupled to a steel line. Why steel? Because the identical aluminum line broke in not very many hours. Why aluminum? Because I went through several flex lines, all of which would not withstand the radiant heat from the 4-into-1 exhaust. Got hard and cracked, melted, whatever.

The kicker? Despite fixation of the aft end of the line, engine shake vs the mass of the steel line broke the aluminum sniffle at the cross pin hole. That's when I thought about it and decided to experiment with no sniffle at all.

I did consider making a sniffle valve using a right angle AN fitting as the basis. I think Mooney used a right angle sniffle. They are just a little ball and a retainer pin. Might still do it, as it would allow running a line directly aft. Maybe Don Rivera would add it to his parts list.

Quote:
Consider this—— the plans for the FAB box which is used in vertical draft intake systems call for drain holes for the very same reasons I mentioned in my post last night. Why would we NOT have drain holes in the intake of the horizontal intake systems????Vic
I think most of the horizontal induction guys do have drain holes in our airbox or snorkel, although a few builders miss it. I do for sure, and designed the airbox with rainwater in mind.



Thread title is "Sniffle Valve Required". The strict answer is no. However, it's not a trivial decision, and we agree it is good insurance.
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  #38  
Old 01-16-2020, 09:23 AM
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William Slaughter William Slaughter is offline
 
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Quote:
Originally Posted by DanH View Post
Tell us about the exit. Intake water is one thing, but I assume you don't approve of dumping priming fuel into the lower cowl.

I too would like to hear about the exit. I have a sniffle valve, but have been operating without it because I couldn't see a reasonable way to route the drain overboard. I have the same 4:1 exhaust as shown by Dan.
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