chivas

I've mounted a Saito 100 inverted. The centerline of the main fuel tank is about 1.5 inches above the carb centerline. I'm having fuel mixture problems. Presume neither can be moved. Any solutions? Header tanks? Fuel Regulators? Fuel Pumps? Uniflow system?

I've read a lot on this and I hear a lot of conflicting info...

I would love any thoughts you have.

alan0899

G'day Mate,
I bet it is running lean as tank level drops, & you can't get enough fuel up to it.
Lower the tank, centre line must be even with or no more than 1/4 to 3/8 below the needle valve, then tune it properly, use this web page,
http://saito-engines.info/throttle_setup.html
Then you won't need pumps or regulators, or anything else to make it run sweet. Not even on board glow.
Tank height is the number one problem with inverted engines, of any size.
Get that right & the motor will run right, get it wrong & you know what happens, because it is happening to you now.

chivas

I can't move the tank any lower. Presuming I can't move the tank or the carb, any thoughts?

khodges

My Feedback: (1)

If your tank is so much higher than the carb, it's probably a Rich condition instead of a lean one. You could try running without the exhaust tap to the tank, or put a regulator in the fuel line. Ideally, the tank centerline should be no more than 3/8 to 1/2 inch higher than the spraybar on the carb.

alan0899

G'day Mate,
Sorry, stupid me, I thought the carb was above the tank, I need to clean my glasses more.

Are you sure you can't move the tank, or swing the motor 90 Degrees, so it's sitting sideways.
Don't know what the plane is, but that would be the best, if not the easiest solution.

chivas

I agree that it seems to be running rich. When I try to lean it out on the low end, it seems to cut off the fuel flow, chokes and dies.
I'd really like to avoid changing the orientation of the engine, even though it is a good suggestion.
Would the regulator work? It makes sense, but I've heard some feedback that they wouldn't fix this problem, but I don't quite understand why.

R8893

My Feedback: (20)

I have successfluuy dealt with this situation in a Hurricane with use of a Cline regulator. Also in a Typhoon using an OS 1.20 with a pump (hence regulator). Just finished a Ki-61 Tony with similar, but less extreme, situation. If necessary I will experiment with uniflow on the Tony.
Chuck

KC36330

something that may be way out there in left field but i recently ran into a problem with an inverted OS70 (which I've ran inverted many many times with no problems), what ended up being the problem was the orientation of the pressure tap on the muffler, with the tap pointed down oil in the exhaust would get passed up through the vent to the fuel tank, as the oil was passing up the fuel tubing it caused the engine to lean then at is was free of any oil it would richen back up. i turned it so the vent was pointed up and that cured the problem. just something you might check.

I've also ran header tanks with inverted 2 strokers with good results.

kc

rclement

My Feedback: (1)

Sounds to me like you need cline regulator. Same situation that exsists on the 60 size U Can Do.

chivas

A Perry pump is $20. A Cline regulator is about $50+. I wonder if the pump will serve the same purpose in this context as the regulator...

KC36330

Cline regulators or the Ironbay regulators are great where the fuel system is Above the carb the Perry pump is great when the tank is Below the carb, the regulators will stop fuel flow when the engine is not running, the Perry pump will allow fuel to siphon into the carb and flood when the engine is not running.

kc

chivas

Cline's regulator is $60, Iron Bay's is $43. Any new opinions on relative quality?

Of course, these issues have been discussed some before, but more in the context of putting the tank on the CG:
[link]http://www.rcuniverse.com/forum/m_1737794/anchors_1741346/mpage_1/key_/anchor/tm.htm#1741346[/link]

chivas

The links:

Iron Bay: [link]http://www.ironbaymodelcompany.com/Webpages/Accessories/Accessories.html[/link]
Cline Regulator: [link]http://www.billsroom.com/pcfs/products/CFS/fuelsysdesc.htm[/link]
Perry: [link]http://www.perrypumps.com/prod02.htm[/link]

Interestingly, the Perry pumps that operate off of crankcase pulses (VP30) claim to have a regulator feature (which would presumably defeat siphoning). The vibrational activated pumps (VP20) are silent on this point:

"The VP-30 regulating pump is capable of performing like no other fuel delivery system. It delivers an ideal .25 PSI to any model carburetor from a .15 to a 3.0 cu.in. engine. The pressure remains constant throughout the entire speed range, making the carburetor adjustment easy and simple. Once the needle valve is adjusted, the mixture will not vary regardless of how low the fuel or the attitude of the airplane, thus eliminating rich/lean runs altogether."

"The VP-20 pump for your 4-cycle engine is used by thousands of modelers throughout the world because it is trouble free and provides the most reliable fuel delivery to your 4-cycle engine. This pump mounts to the front or back of the crankcase, on a mounting plate supplied with the VP-20 and 22SG pumps. The pumps are actuated by engine vibration. May also be used for 2-cycle engines. Not recommended for opposed multi-cylinder engines."

WRM

Chivs
I had the same Problem. You will not believe how I fixed it.[sm=wink_smile.gif] I put a Saito F-1 Fuel filter below the carb . The F-1 will stop it from syphoning the fuel.

daubut

Hadthe same problem with a GP Tiger Moth, I upgraded the stock 12oz tank to a sullivan round 16oz tank. This put the tubing lines about 1" higher than the center of the carb. I installed a Sullivan Anti Siphon Valve $8.50 @ Tower Hobbies between the supply line and the needle valve. No more siphoning problem and the engine runs fine, it's inverted and seems to have no problems while rolling, looping and making basic manuevers.

chivas

Cool. Great suggestions!

WRM

I installed a Sullivan Anti Siphon Valve on my Mayham 40 an it is GREAT![sm=thumbup.gif]