razorice79

My Feedback: (1)

hello, I have a question I have a 0s.91 with two 11oz main tanks mounted below engine in wings of the mirage.. and a 2oz hopper tank mounted in the fuselage by the engine.. everytime i run the engine it dies out after like 1-2 mins of use.. its not running lean, i have plenty of smoke coming out.. but seems like once the fuel is burned out of the hopper tank, the fuel isnt coming up from the main tanks.. im using medium size fuel tubing.. and a JMP fan pressure vent for my pressure to main tanks.. does anyone suggest me getting a fuel pump for my 0s91. or should i change my setup some how? what fuel pump would you recommended and has anyone ever used a fuel pump on these engines? thanks btw, im using a BVM inflight mixture... thanks for all your help, im sure a few of you guys have some experence with this problem...

-Razor

Phil Cole

If the hopper tank is emptying without drawing fuel from the main tanks you either have an air leak between the hopper and main tanks (or a leaking hopper), or your plumbing isn't correct.

The hopper should remain full until at least one of the main tanks is empty, depend on whether you have a tee going to the main tanks, or have them in series.

You can easily test the system by connecting a fuel-filler pump to the tubing that connects to the main needle valve. Fill the system and then block the vent(s).
Try the pump in both directions. Look for fuel squirting out or air bubbles entering.

I came back to add that a pump is not going to help if the hopper is running dry first, but Gary replied simultaneously with me.

grbaker

My Feedback: (29)

Before trying a pump, I would try pipe pressure from your tuned pipe instead of the pitot pressure.

After it dies, is the hopper tank dry?

With all tanks full, can you de-fuel all the tanks by pumping the fuel out of the hopper (using the tube that feeds the engine)?

razorice79

My Feedback: (1)

i cant see if the hopper is dry without taking the whole duct/fan/tube setup out.. but i can see that there isnt strong fuel flow coming from it after like 1-2mins of run time.. yes, i can pump out all the fuel i put in through a qwik fueler value between the lead line from hopper to pick up line to bvm flight valve.

razorice79

My Feedback: (1)

i have them running in series off the pivot pressure vent.. im using large fuel turbing for the main pressure line to first main tank.. and the rest is medium sized.. should i try all large tubing? or is medium tubing ok for os91.. thanks for the info..

Darryl Usher

The hopper tank is drawing air. Somewhere you have air leak. Use drilled out clunk, 5/32 tubing and large fuel lines.
Darryl Usher

volkan

ok, while we are on the subject, ive been wondering (while in boring English and German lessons)
what uses more fuel

Os .91 (DF) or simmilar, or a standred turbine (P120??)

also whats cheaper Jet A (or whatever you use) or %5??

grbaker

My Feedback: (29)

OS.91 burns 2oz of fuel a minute. Last time I bought 5% ducted fan fuel it was about $14.00 a gallon.

On my P120 powered Facet I burn about 10oz of Kero a minute. @ about $4.50 a gallon.

volkan

ummm, i guess you want me to do the math...turbine is better (BUT BLOODY EXPENSIVE) what about pulse jets, how much fuel,
i think that would be the cheapest though, unleaded!

grbaker

My Feedback: (29)

Forgot to mention that most of the Facet flight is at 1/2 throttle.

joeflyer

My Feedback: (48)

Razor,
You are having this problem because fan pressure simply cannot provide enough push to get fuel to the hopper. The fact that the main tanks are mounted below the engine and are plumbed in series means you'll need lots of pressure to move the fuel. You should never mount tanks below the engine if you can help it, perhaps there was something interfering with putting them in the proper location.

Gary is on the right track. I would recommend pipe pressure AND plumbing the main tanks in parallel. If that doesn't work then relocate the main tanks on each side of the ductwork so that the centers of the tanks are approximately even with the center of the carburetor. That setup works on every ducted fan I've had.

It is possible that you do have an air leak compounding the problem, but I seriously doubt that you'll ever get your current setup it to work right even if it is leak free.

Joe

Randy M.

My Feedback: (38)

Razor, I see you mentioned a quick fill valve, does it have it's own line to the tank? or is a dubro type- when you plug into it to fill, it cuts flow to carb, when you unplug, flow is restored. I would not use one of this type unless it was for fill only. I've seen them leak on several occasions, plus I don't know if it would flow enough fuel for the engine. I've been using fan pressure for 10 yrs. now with no problems. It's in the plumbing. Petot to vent tube, to tee, to vent on main tanks. from main clunks to tee, to hopper vent , hopper clunk to carb. Tanks should be as close to center with carb as possible. If properly plumbed you should pull fuel into hopper, not air. You have a leak or you have a vent line wrong.
I hope this helps.
Randy

Randy M.

My Feedback: (38)

grbaker,
$4.50 a gal. seems high to me. I get kero at $1.89 gal plus $5.00 a quart oil per 5 gals. Roughly $2.89 per gal.

grbaker

My Feedback: (29)

Actually the fuel I burned last weekend was about $5.20 a gallon. $19 for 5 gallons of Kero and $7 for the oil. my next batch of fuel will be cheaper because I bought some 5 gallon cans of kero for $5 each.

razorice79

My Feedback: (1)

its like a dubro type where it shuts off fuel to engine.. i'll get some "T"s and hoook up the tanks as told.. ALL my fuel line is brand new.. right now i got it running in series and the hopper lead line is going through that quik fueler then to bvm flight mixture then to carb. LOTS of tubing.. just not enough pressure to get a good feed..

grbaker

My Feedback: (29)

I'm with Joe, I doubt you will have much luck getting it to run consistantly with the tanks below the engine. I would do away with the fill valve. Just pull a fuel line loose to fill.

Is there any way you can raise the tanks?

Good luck.

b17flyer

My Feedback: (32)

if unable to pull line from carb. Need to go to a 3line system. Two(2) lines with clunks and a vent. One p/u to carb and plug the other when not fueling or defueling. This rarly leaks unless the line has a hole or YOU FORGET TO PLUG IT. Unless the system is restricted on the final vent , It is always easyer to fuel the tanks then trying to push past the needle valve. You could always clamp the other line if you want.

razorice79

My Feedback: (1)

i dont think i have enough room, to move main tanks.. this is a JHH mirage older kit, 2 cutouts are their in the wing below fan/engine setup..

rongreg13

My Feedback: (129)

You should give one of Iron Bay's fuel regulators a try. I've got them in 3 of my ducted fan planes right now and if setup correctly, I swear by them. As long as you have a leak-free fuel system and a reliable pressure source, you will not have any fuel feed problems no matter where you place your tanks. An added benefit is that the mixure stays constant even as fuel levels decrease. I use crankcase pressure on 2 of my OS91's and the other uses pipe pressure from a Weston pipe. Either way is equally as reliable, but I prefer the crankcase pressure just in case the pipe comes loose. That way there is still pressure to the fuel system. Assuming your fuel system is rigged properly with no air leaks, this would probably solve your problem. Just my .02 cents worth.

http://www.ironbaymodelcompany.com/W...Regulator.html

CARS II

My Feedback: (7)

Razorice79 I had a JHH Mirage not to long ago I know that the plans tell you to put the fuel tanks in the wing below the engine and use a fuel pump well forget all that, now days Mirage owners are using two 11oz. Sulivan sadle tanks they are positioned in front of the fan left and right of the intake ducting facing forward kind of tight just enough room to push them into place push them with the tubing facing forward then run the lines back to the engine and fan I also was using a 2oz. hopper tank of oval shape and a BVM in-flight mix. it can go past the engine on the left side the oval shape is the best shape to fit in such a tight spot.

About the fuel sys. that you have right now it just doesn't have enough pressure to push the fuel up to the engine even if you use pipe pressure it will not work it is just not a reliable way to do it, if some how you manage to get the engine running good enough for TO. and you get it to fly, once you throttle back the power the engine will quit running because at idle there is not enough pressure to push the fuel up to the engine. I know all this because I run an engine on a airplane with a fuel sys. like that and out 7 TO. 6 of the landings were without power the engine just quit once I throttle back the only time that I landed with power was because I was running it very very rich so rich that it barely had enough power for TO.

CARS II

My Feedback: (7)

On this pic. you can clearly see the set up of the fuel and pressure lines, the fuel tanks will be forward of the fan instead but still facing forward, the hopper tank is closed to the actual position in the airplane and it is of oval shape, the BVM in flight mix. is also around the spot, you can also see that the fuel line is blue for fuel and the the pressure line is red for hot gas also the filters and I made my own line restrictors out of 1/8 ply one for the hopper tank and one for the pressure line.
One more thing the fill line with afuel plug, never leaks.

Hope all this helps.

CARS II

razorice79

My Feedback: (1)

I just purchased one today have it setup with 2 tanks in parallel, with 2 tees for filling and venting.. my pipe is a macs 15cc tuned pipe. i changed over to pipe pressure, and installed the one-way restrictor on pressure line.. question should my pressure line be as short as possible to gain max. pressure from pipe? right now its probly 12-15inchs long and i can probly take off 5inch.. will this new length after being cut give me a little more pressure? im using blue dubro large fuel line.. and large panther red line for pressure lines..

I ran it earlier and the engine got a little hot after like 5 mins of mid-idle.. so im thinking its needs a little more pressure... i'm going to try it again tomorrow will let you know if it successfully runs through a whole tank of nitro.. then it will be ready..

JohnnyA

My Feedback: (1)

"its like a dubro type where it shuts off fuel to engine"
razorice79,
I'm not clear if you're still running the supply (carb) line through the fueler or not, but thought I'd tell you of a problem I had with an OS .46VRDF in a Patriot. It wouldn't richen up, no matter what I tried until I by-passed the DuBro fueler with a short peice of 1/8"(or 5/32",I can't remember) brass tubing. That did it!
I never would have beleived that an OS .46 required more fuel than the standard sized fueler would supply. I installed a LARGE fueler in its place and it ran great.
JA

razorice79

My Feedback: (1)

I disconnected that fuel and just installed a Iron bay regulator with lagre tubing and 2 tees with plugs for fueling and venting..i just had way to much plumbing in there (ex. 3 tanks, fuel filter,dubro fueler,etc) now im just tring to make it simple.

Johng

My Feedback: (4)

I looked at that Iron Bay regulator and thought it looked like a knock-off of the Cline PCFS. But then I checked the prices. Cline wants $60 for an all-plastic piece while Iron Bay is getting $45 for this one with nice brass fittings. Kudos to Iron Bay.