need advice on my remote sniffle valve...

[KayS]

good morning fellow builders,

i would like to ask for some opinions about my sniffle valve setup.

vans drawing says to put in a sniffle valve in the port on the sump, then put on a rubber hose and a aluminum tube. thing is: on my superior cold air sump the sniffle valve port is obstructed by the crossover exhaust. talked to larry vatterman and he mentioned a remote sniffle valve or something.

here we go: i was putting in a 90-elbow-fitting that is connected with a steel tube to another elbow fitting near the bottom of the firewall. this second fitting points down and i turned a rubber hose over the threaded part of the fitting (the hose sits not lose on the fitting, actually you can srew it on and it's secured with a clamp). the hose is then connected to the sniffle valve the same way i did it with the fitting. the sniffle valve is mounted on a small metal sheet which is in turn bolted to the firewall. i didn't see any other way than to push a rubber grommet over the sniffle valve to mount it in a big hole in the mounting plate. on the bootom side of the sniffle valve there is again a rubber hose and aluminum tube (that i have to cut to final length and secure it to the cowling.

very confusing story so i added some pics. one pic is just there to show that you can build a 7 in a one car garage. :-) i do not know if i found the ultimate solution for the problem or if my setup is complete ****. any thoughts???

thank you
Kay

[leaker311]

and here I thought I was in a tight space

I ran into the same issue with my sniffle valve running into the exhaust. however I mounted one of these bad boys between the sump and the sniffle valve

http://www.aircraftspruce.com/catalog/hapages/an914.php

to keep the sniffle valve as close to the engine as possible. My reasoning was that as soon as the engine starts the valve closes and any fluids still present in the line are now trapped between the valve and the engine. (I am no engineer but I figured that the valve closes due to decreased pressure in the sump "sucking" the valve closed so any fluid in the line will just experience a drop in pressure but will not move because of the now (valve blocked) line. I have no idea what will happen when that line (possibly filled with some fuel) is exposed to the heat of the engine for long periods of time while flying.
Like I said I am no engineer so I chose to prevent instead of guess and keep the valve as close to the sump as possible so the line can still drain, even with the engine running.
I am away from the project so I have no pictures unfortunately...

hope this helps a bit

Marco

[KayS]

Hey Marco,

so using the AN-914 elbow your sniffle valve is mounted horizontally, right? i was thinking about the same but i thought that the sniffle valve has to be mounted vertically to function properly. no idea if i was right here...

ok you wanted to keep the valve as close to the engine as possible... i understand your reasoning behind but i thought that the fuel just collects in the sump during the process of shutting down the engine. so there shouldn't be any fuel when you start the engine and go fly with... or? if there is fuel trapped between the line and the valve, that fuel should vaporize because of the exposure to exhaust heat and goes with the air into the cylinders.... mmhh?? (head scratching)
Kay

PS: thanks for the compliment about my shop. it really shouldn't be less space. i just have to find somebody to clean it up.

Kay

[leaker311]

" i thought that the sniffle valve has to be mounted vertically to function properly. no idea if i was right here... "

Good point, I was wondering the same thing but I figured that with the tail low attitude of a taildragger on the ground the valve (which I think is a just a metal ball) would open... Otherwise you can use a 45 degree fitting (if the exhaust will allow) and then the valve will surely open

"so there shouldn't be any fuel when you start the engine and go fly with... or? if there is fuel trapped between the line and the valve, that fuel should vaporize because of the exposure to exhaust heat and goes with the air into the cylinders.... "

Again a very good point, I almost assume that that would be the case but I just wasn't sure when I mounted mine so I went the route that most resembles the vans suggested setup...

I tend to overthink things thats why my QB turned into a slowbuild

[KayS]

ok, so i assume that both setups are somewhat ok. but i will check if there's room for the 45-degree-fitting...

[ao.frog]

.... the same sump and I used two 90* fittings to move the sniffle valve slightly right. There it was space enough to mount the valve and the tube.





The pics are taken appox underneath # 1 cyl looking aft. (You can see the my homemade throttle bracket (painted grey) and the left exhaust hanger.)

No problems so far.

[KayS]

hi alf olav,

thank you for the pics! the rubber hose looks a little bit close to the exhaust but when you have had no problems with this setup flying it's worth a try...

kay