Hey Guys,

Have any of you had experience using a one-way valve on the muffler pressure line? Does it really work? [sm=spinnyeyes.gif]

Sonnytex

why would you need a "check valve" on the muffler's pressure line? you would have to disconnect the check valve to refuel as the check valve would not allow you to vent the air out of the tank.....the only place I know of a check valve is on a gasser's vent line to keep dirt and crude from entering the tank through the vent..which is on the bottom of the aircraft.....
Good flyin to ya

Depends on what you want to use it for. They 'work' in that they do their job, but whether or not you should have one in your setup is another story.

Just visited a club down in FL and I was talking to a gentlemen and that subject came up. He highly recommends putting a check valve in the exhaust line. It keeps positve pressure on the tank when the engine is at idle. He says it has eliminated the engine dying when you pull the throttle to idle. I pull the line off the muffler when I refuel but I don't know how you would handle that if it was a cowled engine. Anyway thats what he says and I have yet to try it.

chopper man

Ok I don't know much but that sounds like a band aid on another problem. 99% of us don't use check valves on our pressure lines and our engines don't quit when we throttle down. The system is not designed to be pressurized like that. Other systems are.

hmmm...sounds logical...but my engines don't die at idle as it is....things that make you go hmmmmmmm

I've used a valve before but didn't really like it too much. Seemed to me that it caused the eng to run rich at idle and hard to get consistant low speed settings. It would be OK at first (the way you tuned it) but as the pressure dropped after idling a bit (and it always does) the mixture would shift. Ended up doing away with it and was happier. But give it a try, maybe you'll like it.

BTW - valve was on the plane when I bought it, wasn't my idea.

If you are using a typical muffler pressure system and the fuel tank/spray bar (jet) relationship and orientation is reasonable then using a check valve in the muffler pressure line typically will cause excessive head pressure at the needle valve inlet and result in an overly sensitive needle causing inconsistant high speed needle settings and various running problems including flame outs due to leaning in flight.

sonnytex are you trying to fix an actual problem, if so what exactly is the problem. If there is no problem I would suggest you not fix it.


John

Thanks for the comments Guys,

I ran into a situation a while back when using a 4-stroke Thunder Tiger on a "Magic". The engine would run fairly good no matter which way the plane was flying or rolling, inverted flying included. My problem always occured when I attempted a high G manauver as in starting into a tight loop. The engine would just die, no cough, no sputter, just die. If I eased it into verticel it would continue to climb
without a problem. I reoriented the engine on the firewall a couple of times just to be sure the carb was not too high or too low in relation to the tank. I finally gave up on the 4-stroke and put a 2-stroke in it and the plane flys perfectly. So, this problem has been sticking in my head - I digging really low trying to figger this one out - thus the one way valve question. [sm=72_72.gif]

Thanks for your thoughts,
Sonnytex

P.S. The tank, clunk, lines ect. were all checked at least twice. All engine possible air leaks were also checked.

On top of what John said, putting a check valve in most engines that run off of normal muffler pressure will cause many problems. Most of which John has addresses. One that he didn't was an excessive waste of fuel. When you put a check valve in a system that wasn't designed for it you will build up pressure in the tank. Most normal glow engines have no way of checking that pressure in the carb/engine. The excess pressure is going to "force feed" the fuel into the engine. Most of that fuel is going to just get blown out of the exhaust without ever being burned.

Ken

Thanks Ken,

I shall forever more deep six the one way valve idea. I am not exactly a newbie at this (flying since mid 50's) but this problem has really affected my brain. [sm=spinnyeyes.gif] The last plane I had the 4-stroke on flew just fine but now I can't find fault with the engine or the plane. Thanks again.

Sonnytex

sonnytex you being a child and modeler of the fifties as I perhaps you remember the pen bladder tanks all the rage for performance enthusiasts in some controlline and freeflight, Actual fountain pen bladders with a tube inserted and the assembly rubber banded. Penny ballons were also used. Force filled with a fuel bulb and pinched off untill the engine was started on prime then the hemostats were released.

Usually did not work very well due to the high head pressure at the needle. That is untill quite a cottage industry in speed needles developed where small mom and pop suppliers started producing needles for various engines with much finer threads than the stock types thus minimising the sensitive needle syndrome from the high pressure a little more user friendly.


John

Yes, I do remember those days - mostly used on c/l racer at that time. Never actually tried it my self but my Dad was one of the very first to tap into the backplate and try to make his engine run better. Had some trouble with it as best I remember.

sonnytex

And our FireBabys came with the balloon tank that we could use as A pressure tank or A bubbleless tank. I think we tried anything that was new or different back then. People today think the bladder tanks are something new. [8D]

The late great Jim Walker was actually the first to commercialize a presssure tank that consisted of a bladder but the bladder was not pressure filled. Instead it had two boards on each side and rubber bands were slipped around the outside. This allowed some adjustmeni of head pressure by adjustment of the number of rubber bands. The real secret of the success with this system was however because Mr Jim saw fit to design a clever for real pressure regulator into the system therefore avoiding the sensitive needle syndrome completely.

John