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So who else has seen broken sniffle line bracket

Mine, twice so far. Next time I'm drilling a hole and putting it on the other side of the clamp with just the head of the screw above the clamp.
 
I did some FWF inspection today at 46 hours or so, cowling off. Found that the sniffle line bracket was broken, so I replaced it by fabricating a similar piece from stainless steel. I've seen a builders blog where the theory was the exhaust heat weakens the aluminum bracket.

Photos here:

https://turnerb14a.blogspot.com/2019/08/fwf-inspection.html
I found mine broken at around 81 hours. I was thinking either stainless steel, or simply use stainless steel cable which gives it flexibility if the cause is vibration and not heat.
 
I think Van's probably needs to redesign the part or find a better way to support the hose. I'll see how the stainless works - it was pretty easy to fabricate - I happened to have some .018 stainless laying around.
 
Sniffle valve

You might consider just removing the sniffle valve. I?ve never actually used mine.
 
A rubber hose between two adel clamps is all it takes.

The design has the anchor point as the exhaust tube - so you have to use something other than Adel clamp. Van's supplies a small L-shaped piece that clamps to the exhaust tube with stainless hose clamp and the other side of the "L" fits the Adel clamp for the sniffle line. Heat from exhaust + vibration makes the clamp susceptible to breaking.
 
Manifold

How do you account for fuel going into the intake manifold?

That is a reasonable question. I watched my sniffle valve for 300 hours. With the exception of preservative oil coming out when the engine was new I?ve never seen a drop come out of the hose.

I did have issues with the bracket cracking and I needed to reroute the hose because I am working toward a cowl flap system. I looked at the ways to reroute and also considered that the sniffle valve is a potential manifold leak. All those considerations lead me to reinstall the original Lycoming plug.

I cannot say you absolutely should remove your sniffle valve merely that you could consider it. Perhaps I?ve merely been lucky to not need it.
 
As I understand it, sniffle valve is a relatively new tool/addition to the engines as many of my friends who have been flying for many years don't even know what it is or what is it for.
Having said that, I had it on my old engine and the 14 and I always have fuel mixed with a bit of oil draining after shut down. These are typically drops, not pouring out unless I manage to flood the engine. If you run your boost pump excessively and flood your engine, you will see it dripping out of the sniffle valve, if not plugged or inop.

Marvin,
The cowl flap surely couldn't be for the CHT as I recall you had no issues with CHT. Are you restricting the outlet or expanding by the use of cowl flap.
 
Cowl flap

Restricting the outlet if I can do so without restricting the oil cooler outflow. There is precious little space for an oil cooler outlet duct and the required fabrication may exceed my skill set. That is my current concern. I have already sealed the propeller and the cowl to landing gear areas. In all honesty all that work is only worth 2 to 3 knots. It is more of a personal interest.
 
As I understand it, sniffle valve is a relatively new tool/addition to the engines as many of my friends who have been flying for many years don't even know what it is or what is it for.
Having said that, I had it on my old engine and the 14 and I always have fuel mixed with a bit of oil draining after shut down. These are typically drops, not pouring out unless I manage to flood the engine. If you run your boost pump excessively and flood your engine, you will see it dripping out of the sniffle valve, if not plugged or inop.

Marvin,
The cowl flap surely couldn't be for the CHT as I recall you had no issues with CHT. Are you restricting the outlet or expanding by the use of cowl flap.

I see a few drops of fuel stained with oil after each flight as you do.
 
A small amount of fuel from the sniffle after shutdown would suggest a standard Bendix type injection. Marvin and I don't get those drips. He has a SDS EFI, and I have an AFP constant flow with a purge valve.

The SDS won't allow flow into the intake port after shutdown because the injector pintles are closed.

A purge valve vents system fuel pressure to the return line. That allows the spring in the divider to close its outlet. The only fuel remaining which can reach the ports is the wee bit in the small diameter injector lines, and then (for the most part) only if it boils.

The small fuel risk with a standard Bendix style system (Bendix, Precision, Avstar) is 25~30 psi captured downstream of the engine driven pump after the engine stops turning. Several conditions must be met to put measurable fuel in the sump. First the engine has to stop with the fuel pump pushrod on the pump cam's base circle, because that allows the fuel pump spring to continue applying pressure to the diaphragm. Next, the pump's inlet poppet must be leak free, or the pressure would just vent back to the tank. Third, the mixture valve in the fuel controller has to have a leak rate. Most do, but the leak rate for a typical disk-style valve is quite low. Note even if the conditions line up, the most fuel the system can dump on its own into a closed, no sniffle horizontal plenum equals the volume of the pump...which is not going to be a problem.

So, forget the few drops you might see after parking. The real reason for a sniffle valve is to drain away excess fuel from boost pump operation prior to start. Consider the fellow who flips on the pump, then gets distracted. With a gallon or so in the sump plenum, there's a pretty good chance of sucking enough up an intake pipe to cause a hydraulic lock, and bend a rod.

The other potential risk is water, like filling the horizontal sump plenum with a hose while washing, or a taildragger with a snorkel parked just the wrong way in a rainstorm. Like Marvin, I'm not going to tell you to remove yours. You'll need to think about the details and decide for yourself.
 
The other potential risk is water, like filling the horizontal sump plenum with a hose while washing, or a taildragger with a snorkel parked just the wrong way in a rainstorm.

I would suggest that there is a third risk......

A bunch of fuel in the sump because of a botched engine start.
It is not something that happens all the time... In fact I would say that it is most common with people that are new to their new RV and typically new to starting a fuel injected engine as well.

A bunch of fuel in the sump isn't automatically going to end badly, but it can....
 
So when I found the clip broken where the sniffle line is held onto the exhaust at 5 hours I just removed the clip and Adel there. The rubber line is attached at the sniffle valve and at the adel aft of the lower cowl closeout. At 60 hours I can't find any evidence of fatigue on either end.
 
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