Sniffle valve for water too?

[kkmarshall]

I would definitely change the oil if water came out the exhaust!

Keith

[Tbone]

Pour a few cups of water in you oil sump and tell me that it instantly burns off before potential damage to bearings or compromise the lubricity of the oil....It does take some time at temperature to burn off the condensation of the combustion process. I would change the oil immediately in my engine if water was sitting on my pistons and hydraulic locked my engine. I have seen the damage that can do to a engine. Lucky to not bend a connecting rod.

[AX-O]

Originally Posted by rv8ch

Axel, can you tell us more about this? Never heard of one failing.

Not much to explain. The valve failed open on both occasions. a known problem discussed here over the years. Not sure why it happen.

I had this one. http://www.vansaircraft.com/cgi-bin/...=Sniffle-valve

[BillL]

Originally Posted by AX-O

Not much to explain. The valve failed open on both occasions. a known problem discussed here over the years. Not sure why it happen.

I had this one. http://www.vansaircraft.com/cgi-bin/...=Sniffle-valve

Rhonda Barrett said that a certain brand was recommended as others were always going to fail. Sorry I don't remember (silly me) what she recommended, but if my Vans part fails she will be my first call. If any one knows, please post.

[Bavafa]

I have drilled a 1/8" size hole at the bottom of my snorkel for this reason. Of course I know to plug my inlet if there is a chance of rain, at least the left side but the drain hole is an insurance for the water not to get to the intake.

[SJordan]

Originally Posted by BillL

Rhonda Barrett said that a certain brand was recommended as others were always going to fail. Sorry I don't remember (silly me) what she recommended, but if my Vans part fails she will be my first call. If any one knows, please post.

I just opened a box from Don at Air Flow Performance with a great looking sniffle valve! $25.

http://airflowperformance.com/index....anifold-drain/

Looks like Don calls it a "manifold drain"

Now that I think of it, this valve requires slight vacuum to shut. With ram air induction there will be a slight increase in MP over lower cowl pressure I would think and thus the valve will not shut?

[Kevin Horton]

My RV-8 also has the horizontal induction, and I got some water in there once after sitting out in rain overnight. I now make it a practice to pull the prop through at least two complete revolutions if the aircraft has sat outside in any rain. Of course I make sure the ignitions are both off, and the throttle is at idle, and the plane is still tied down when I do this.

[DanH]

Originally Posted by SJordan

Now that I think of it, this valve requires slight vacuum to shut. With ram air induction there will be a slight increase in MP over lower cowl pressure I would think and thus the valve will not shut?

Depends.

Assume a "worst case", lots of airspeed down low. A 360 at 2450 sucking through a 3 inch ring and moving at 185 KTAS would have an available intake pressure rise (above freestream pressure) of about 11.5 inches H20. Typical lower cowl pressure (stock RV cowl) would ballpark at 4 inches H2O above freestream. The difference is 7.5 positive, so we might think the sniffle will be open.

However, there is a wild card; pressure loss at the throttle body (and filter if present). I don't have exact values for 255 CFM, but an educated guess says an old RSA-5 sucking through a small filter would result in a negative value at the sniffle, while an FM-200 and no filter would remain positive at the sniffle. A guy with a variable cowl exit might close it, raising lower cowl pressure, and easily closing the valve even with an FM-200.

Good news is that it doesn't matter. The leak can only happen at high airspeed, meaning high power, where the leak is a tiny percentage of total mass flow into the engine. A slight positive leak merely fools the system into supplying a wee bit more fuel, which is perfectly safe for the engine, and the pilot would lean to whatever he wants anyway.

[SJordan]

Originally Posted by DanH

Depends.

Assume a "worst case", lots of airspeed down low. A 360 at 2450 sucking through a 3 inch ring and moving at 185 KTAS would have an available intake pressure rise (above freestream pressure) of about 11.5 inches H20. Typical lower cowl pressure (stock RV cowl) would ballpark at 4 inches H2O above freestream. The difference is 7.5 positive, so we might think the sniffle will be open.

However, there is a wild card; pressure loss at the throttle body (and filter if present). I don't have exact values for 255 CFM, but an educated guess says an old RSA-5 sucking through a small filter would result in a negative value at the sniffle, while an FM-200 and no filter would remain positive at the sniffle. A guy with a variable cowl exit might close it, raising lower cowl pressure, and easily closing the valve even with an FM-200.

Good news is that it doesn't matter. The leak can only happen at high airspeed, meaning high power, where the leak is a tiny percentage of total mass flow into the engine. A slight positive leak merely fools the system into supplying a wee bit more fuel, which is perfectly safe for the engine, and the pilot would lean to whatever he wants anyway.

Solid thought process Dan! The valve open 100% of the time would definitely equal no noticeable difference the leak is so small just might as well drill a small hole in a plug at that point. I agree though the valve will most likely still close most of the time.

[RV7A Flyer]

Originally Posted by AX-O

Not much to explain. The valve failed open on both occasions. a known problem discussed here over the years. Not sure why it happen.

[/url]

So what happened? How did you identify the valve as the problem?

And how would one test this valve *without disassembling things like drain hoses and such, or removing the valve from the case* during, say, annual CI?