I'd like to know how many people out there are running large glow engines, such as the st2300, OS 160, BGX, Moki 180, etc with a "standard" fuel system. When I say standard, I mean, muffler pressure, no pumps or regulators, tank near the engine, no check valves, no header tanks, etc. More specifically, has anyone gotten acceptable results by just using large fuel line from the clunk to the carb,(along with large brass in tank)? Acceptable results means that the airplane is capable of all aerobatics, and the engine doesn't go lean or quit in flight. I know many of us are using pumps and regulators to get the tank back on the cg, but would we still want to use them if we weren't concerned about the cg shift? I have my own set of opinions on this, but I'd like to hear from some of you who have done the flight testing to support your comments.

Thanks guys!

I have run a ST 2300 in the past and am currently running an O.S. 1.60. I have not used a pump on either or these engines. I did make some mods to the ST carb to solve the mid-range problems. In both of my engines I am running medium size fuel line. On the ST I ran the stock muffler, but did plug one of the outlets. On the O.S. I am running a Bisson pitts muffler and also plugged one of the outlets. On both engines mixture has been consistent throughout the flight. I am also using O.S. "F" glow plugs in both engines. Both engines are excellent in aerobatics. The ST was in an old style Ultra Stick. The O.S. is currently in a 1/4 scale Aeroworks Edge 540. Both have unlimited vertical. Both engines have been very reliable and more than adequate for the task!

I hope you find some of this interesting.

Steve

I take it the 2300 you had was an Italian one? I have the new one with the carb barrel slot fixed. Mine has no midrange problems. It has an occasional surging in level flight, and goes lean in a right wing high knife edge. Also running F plug and 10% powermaster. Engine has 2/3 of a gal thru it so far.

Yes, my ST 2300 is one of the Italian made engines. I still have mine and am building a new plane for it. I have not had any of the problems you describe. Is it possible you might have a problem with the fuel pick up in your tank?

Steve

I've run ST, and Moki engines with the tank near the firewall. Works fine with large fuel tubing.

Only mods I made was to buy OS7D carbs for all my ST engines.

I always ran my big glow engines on 5% Omega fuel. High compression--European--engines. Don't need fancy plugs or lots of nitro. Omega is 30% castor and 70% synthetic--17% total oil. Thats good protection against lean runs and it won't overheat the engine. It's also the cheapest glow fuel around here.

Inverted engines:
I just moved my tank down so that it was CL with the carb spraybar. Used On-board glow a couple times. But, after break in---SEVERAL gallons--they would smooth out and the on-board glow was really only a convenient way to start a cowled engine.

It will smooth out after about 4 or 5 gallons of fuel.

Maybe drop the nitro to 5%. Not a big deal though. Just don't bump nitro up to 15% or you'll have lots of problems.

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Large fuel tubing is a must with these engines.

Surging is a sign of not enough fuel getting to the engine. A kink or unnoticed obstruction can cause this, as well as fuel tubing that is not large enough. Resist the urge to have extra fuel tubing flopping about. This can affect fuel delivery much more than one would suppose.

I'm tagging along on this post, not addressing this poster. Thanks for the ride! <G>

I like the composition of your fuel choice, (this poster).

I'm currently running a ST 3000 with an OS carb
and 2 OS 1.60 2 strokes. All of the above run fine
on muffler pressure. I will point out however that
I'm a civilian scale guy and I only do mild aerobatics.
And yes, I use the large fuel tubing.

Regards
Roby

Nope not satisfied. Mixture changes from fill to empty tank causing changes in engine performance, engine uses more fuel, engine leans out in vertical attitudes. So I actually tried my Moki 1.80 with and without the pump/reg and went back to it right away. The benefits were very apparent to me.

But I can totally understand why people would prefer to keep it simple. They may not care about the reasons I posted above and just tune the engine very rich so it never goes lean. They may also not be putting the plane in vertical attitudes or hard acclerations like 3D or other aerobatic planes experience. So it's all about personal preference and flying habits/setups.

In my experience the big glow engines run fine if you have the tank right behind the engine.
The problem being is that the big thirsty engines need large tanks if you want to fly for more than 5 minutes; when you run a large tank (over 20 oz) right behind the engine the airplane is so nose heavy at the beginning of the flight that performance suffers. (anyone that says it doesn't is obviously not an experienced pattern or imac pilot.) On my moki's I tried using header tanks, both styles of perry pumps. none of that garbage worked to my satisfaction. finnaly I purchased a cline regulator and all my problems went away and I have my 24 oz tank on the c.g.

Thanks people! These are the things i want to hear. I have a vp30 to use if I need to, but would rather not if I can get away with it. On the Funtana 90, the cg shift during flight does not require a trim change, so I don't really notice it. I am not after 3D with the 2300, even though it's on an F90. I will be putting it on a Goldberg Sukhoi after I am sure it performs up to my expectations. I really like the engine alot. Flying behind an 18" prop is fun, to say the least. I will be changing the fuel line to large before I fly again, and i'll make sure the clunk isn't too far back. If this doesn't quite get it, I'll add a one way valve in the pressure line from the muffler. At least I know now that what I am asking from this engine, others have achieved. Thanks again!

I have tried the "one way valve" from the muffler to the tank as you mentioned but my engine got very strange and was impossible to tune properly. Have you had good luck with "one way valves"??
Reducing the innerdiameter in the throttle barrel by putting a sleeve in there is a good way for better fueldraw.

Nope, never tried a check valve. I've only heard of them being used, never seen one. I think my particular problem could be associated with the medium fuel tubing and perhaps the clunk being too close to the rear of the tank.

I'm not into modifying carbs. If the stock one won't work, I will go with a Perry. I have had good luck with those, but I think the stock one is a much better piece.

Do yourself a BIG favor; if the stock set-up doesn't work for you, get a Cline regulator instead of the VP 30 pump.

You have a link to where I can get one? I haven't been able to locate one.

http://www.billsroom.com/pcfs/

It's better to call him and order over the phone. He's not setup for online purchases.

Large fuel tubing is NOT needed for the S.T. 3000.

Even the 4500 draws fuel satisfactorily through medium fuel line.

FBD.

That is in contrast to everything else I have read. This 2300 is my largest engine to date. It acts as if it could use more fuel pressure to the needle, as the needle is not sensitive at all. I would rather have to zero it in to within 5 clicks than to one full turn. Restricting the exhaust is one way to improve fuel pressure, but there is a downside to too much back pressure also. I think going with the large fuel tubing can only help, and can't possibly hurt.

Don't believe everything you read. I own and operate a S.T. 3000, and it runs
fine on medium fuel tubing. My flyin' Bud has a 4500, it runs fine on medium
fuel tubing as well.

If you want to quote, and contradict me....please do it with facts and experience.

Flyboy Dave.

The 2300 that I am currently running needed a little help with fuel draw. I suspected the venturi is too large for the rpm I'm turning, which is 9300. I made a sleeve from K&S tubing, reducing the barrel diameter by .030". This mod made the needle respond noticeably better. Now I can set the needle for a rich two-cycle on the ground and finish the tank with complete reliability. I am using 5% Omega, stock muffler, stock plug, and a 14 oz tank mounted close for 10 minutes in the air. After some run time and carb tuning this engine has become about as user friendly as my trusty OS108, and thats tough to beat.

If you run a check valve from muffler to the fuel tank you will then need a pressure regulator. I would imagine it to be a rare set of circumstances when you did not need the pressure regulator.

Many years ago, when I was flying pattern, OS decided to cheat in the horsepower race by hugely increasing the size of their carburetors. They began using the carb for the 1.08 on their then new .61 FSR. The carb was so large that they fitted it with a throat restrictor. The problem was, even with the throat restrictor, there just wasn't enough air flow through the carb for it to work right. Yeah, it was okay as it was for sport flying, but not for pattern. A pump/regulator was needed.

Rossi, on the other hand, had engines that developed their power through porting/engineering. They ran smaller flow carbs, but still produced more horsepower because of the sophistication of the innards of the engine. Those Rossis did not need a pump, for the most part.

Ever since OS fitted their .61 FSR with too large a carb for good throttling, we have had this problem of having to run a pump/regulator. Before that, most engines ran just fine with muffler pressure only. I wish the manufacturers would begin reducing the throat size of their carbs and begin utilizing better porting/timing for further horsepower increases. In fact, most engines are producing more horsepower than we really need these days. They can further reduce carb throat sizes to accommodate 3D throttling requirements. Enough of this blasted horsepower race. Tractability (engine throttling) is at least as important as gross brake horsepower on a dyno.

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Depends on how much nitro you are burning. On 5% or less, you may be right.

I've never ran anything but 15% Power Master in the big Tiger.

Same fuel I ran in every Tiger I've owned. What would the nitro content have to
do with the amount of fluid that can be drawn through the line.

FBD.

I appreciate your input on this matter. However, I don't appreciate your tone of voice. As a moderator, I would think you would be able to find a better choice of words.

running my St2300 with medium fuel line. I have also used it on my Spacewalker II without a pump and on my F90 with a pump. My Os 1.60 is used with a pump and medium line. It all depends on fuel tank position whether you need a pump or not. Medium line has worked fine for me on all my large engines (OS 1.60, ST 2300, ST 2500)