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Do you use pressure on your fuel system?

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Do you use pressure on your fuel system?

Old 12-24-2001, 10:24 PM
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Tex Pilot
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Default Do you use pressure on your fuel system?

Hello all. We have been flying without pressure on our 4-strokes for a while now. A *seasoned* flying friend told me that I didn't need presure if my tank center was located within about 1/4 to 1/2 an inch below the center line of the carb......... the area with the spray bar. He said that running pressure only added carbon to the tank and alowed junk to get into the tank....... resulting in a poor running engine within a short time. If you use fuel filters this helps..... but I like to filter my fuel before it goes into the tank. My engines seem to do just fine this way inverted flight or not....... it just doesn't matter. Just checking for some feedback........ Anyone else do this? Tex

edited to add that this is for 4-strokes only. I don't know about 2-strokes.
Old 12-25-2001, 01:53 AM
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Default Pressure fuel system

On a glow engine without a pump I use the mufflers pressure to the tank using a fliter in the line.
Old 12-25-2001, 02:51 AM
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GUNSHIPGUNNER
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Default Do you use pressure on your fuel system?

Having my own flying field makes it easy for me to fly every day the weather allows. I use about 25 gallons a year in various size aircraft.

All my planes have either pressure from the muffler, the engine back plate or pumps.

And in over 33 years of flying I have never heard of experienced fuel tank carboning!!

One Of my Sig Somethin' Extra's has over 300 flights on it using the same tank. I have tried several different engines on this bird including 2 and 4 strokes and the tank is still as clear as ever.

Muffler pressure (tuned pipe pressure) is so easy to set up and it has been my experience that it provides you with a more consistent needle setting regardless of where you locate the fuel tank.

What happens when the tank is perfectly in line with the carb but it is directly BELOW the carb because you are either climbing vertical or hovering? Can you say "fuel starvation" which can lead to serious engine damage due to a overly lean condition?

My suggestion would be for you to refer to either Dave Gierkie the engine guy from Model Airplane News or the master himself, Clarence Lee who writes a column for RCM. Both of these "Seasoned" engine experts always say to use either a pump or engine / muffler pressure.
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Old 12-25-2001, 03:09 AM
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Default Pump!

I always run a pump, from the exhaust or a purchased unit to aid in it. The only time I have not run one is on a gas engine. You must always keep pressure on the take with a glow engine.
Old 12-25-2001, 04:08 AM
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Tex Pilot
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Default Do you use pressure on your fuel system?

Hello Gunshipgunner. Do you ever take your needle valve out and clean it? I was just wondering what you were cleaning off it when you do. If you do not you are the *only* seasoned pilot that I have heard of that does not. This would be a very unusual condition.

Chook...... You must always use pressure on a tank? I should tell my engines that as they don't know it yet. My engines run just fine without pressure. My needle valve stays clean.

The information about the center of the tank is for a rough gestimate. That is so it is about as close to being in the ideal location as can be....... for example the tank being almost empty..... or almost full.

This is for 4-stroke engines only. I am not talking about 2-strokes. A 4-stroke engine should pull fuel 2 ft. through small fuel lines without any problems.

I am *not* saying this is for everyone. I am just saying what works well for our flying group. Not everyone in our flying group does this. Just 90% of them. The others are not sold on it. They still have to clean their needle valve.

If you will read my post........ I am asking for feedback on what experience others have had with this. If you have never tried it...... then please don't say it will *not* work, and work fine.

The only real benefit other than a clean fuel system is not having a pressure line running to the muffler. It looks a lot better without it. JMHO Merry Christmas, Tex
Old 12-25-2001, 08:07 AM
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Default Do you use pressure on your fuel system?

You asked the question, not me.

You asked what other did, not me.

I referenced well known and reputable engine experts in my reply(just in case you responded to advice like you did). You did not.

Even though I have been flying RC for a long - long time I always read everything I can about it in hopes of learning something new and I learn something new very often this way.

You seemed to express a considerable amount of fear and anger in your reply. Lighten up a bit. After all we are only talking about little toy airplanes here not World peace.

"Contemp prior to investigation will forever keep a man in darkness"
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Old 12-25-2001, 11:27 PM
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Default Do you use pressure on your fuel system?

Sorry Gunshipper if you thought my reply was with fear and / or anger. It was not meant to be that way. I was only trying to say that if you have not tried this......... then how can you say it does not work. I am proud that the experts run pressure. If it works best for them...... then thats great. I am only telling the few that think they would like to know........ you don't have to run pressure on your 4-strokes. We have checked performance with a tach..... using same engine and fuel and prop. No better with the pressure line. I like the clean look of the plane without the pressure line running to the muffler. It is very simple to run pressure......... but if it is not needed....... I don't think I will use it.

My *seasoned* friend let me in on this well kept secret. You can use it........ or you can rebute it ......... I like all the responses....... its just that when someone tells me that my engines will not run that way......... I guess I just forgot to tell them ..... cause they are still running happily. Thanks for your reply, and have a Merry Christmas! I really mean it........ no ugly replies coming from this direction. I'm really not mad.... or in fear......
edited to add. You will have to change your high speed needle setting. You will realize a much greater range of adjustment..... less finicky with your engine not changing with just one click of the needle. Try it!
Old 12-27-2001, 03:45 AM
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Default pressure

Fuel tank pressure (from whatever source) is only an aid in delivering fuel to the carby whether it be 2 stroke or 4 stroke. The primary means is by the depression in the carb venturi. The use of pressure will not give ANY increase in revs or power but it does allow a more consistent mixture from start to finish and at varying attitudes (particularly with an almost empty tank and going vertical or hovering....a worst case scenario).
My preference is to always try a new model/engine combination without pressure and if it works OK then why complicate things? Most 2 strokes however have a carb that's way too big for the revs normally used (advertised HP sells engines) in which case pressure could be a necessary evil. 4 strokes, from what I've seen, seem to have a much more suitably sized carb and being mounted at the back of the engine give less head of fuel to be drawn when going vertical or hovering.
The problem with carbon getting into the tank when using muffler pressure would really only happen if using castor in the fuel. There's the tradeoff...the best possible oil but does produce minute carbon particles, some of which must find their way into the tank although I've never had any problem with it. However most 4 strokes use synthetics anyway to avoid carbon build up on the exhaust valve.
Old 12-27-2001, 12:03 PM
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Default Do you use pressure on your fuel system?

It's interesting that YS decided to pressurize their 4 strokes long before they began supercharging them.

As the YS engines line was initially developed for pattern flying, the need for instantaneous throttle response was a given.

That is why YS and most other 4 stroke engine makers suggest you use either pump, crankcase or muffler pressure.

As for "complicating" things I must be missing something.

Every fuel tank requires at least 2 lines. One to provide the fuel and one to vent the tank. If you don't run muffler pressure then
the vent line STILL needs to go somewhere and unless your careful fuel will pour out of the vent line when the plane is in certain attitudes (such as inverted). Running muffler pressure completely prevents this and gives you something to do with the vent line to boot!!

Regarding the use of castor oil. As I stated in an earlier post, I read a lot about what it is I am doing at the time. This way I don't need to re-invent the wheel. I use and have been using a combination of synthetic and castor oil for over 32 years in literally hundreds of engines.

Go on the net and look up the writings of the most knowledgeable engine makers and developers. Clarence Lee, Dave Geirke, and the list is almost endless.

They ALL advocate the use of bean oil in both 2 and 4 stroke glo engines.

Bean oil provides at least an additional 100 degrees F. of protection over any synthetic oil presently used in our engines.
No other substance know to man provides this protection and this is the main reason most of the notable engine Gurus recommend adding at least 2 ounces of Castor oil per gallon to any glo fuel that doesn't already have it in the ingredients.

Another important reason these same fellows suggest you use some bean oil in your fuel is the prevention of corrosion. Corrosion of the engine internals caused by the fact that Nitro actually attracts moisture. After run oil helps prevent this but I for one don't always take the time to use it after every run.


BTW: There is a subset of RCers that REALLY like to spend big money on our hobby and run their engines harder than any other group (except maybe pylon racers) The helicopter guys. And most of them DO NOT like to use ANY bean oil in their engines.

But ask one of the top chopper pilots just how often they rebuild or replace their engines. And it's a well know fact that this shortened engine life is primarily due to lubrication failure.

A quick note regarding pressure and helicopter engines.

EVERYBODY uses muffler or pump pressure on their helicopters. It is a MUST to have a reliable mixture during a run as they run their engines so close to the ragged edge that going slightly lean will destroy a $300.00 engine in a few seconds. And the only way to insure a consistent setting is with a pressurized fuel system of some sort.

Anyway, use what works for you but don't do it just because you want to be different or a 'rebel" . So many guys need to be different so they latch onto an idea that is different from the conventional wisdom in order to stand out in the crowd and be noticed. Maybe in hopes of others thinking them smarter than the rest.

I did that for years and it only cost me time and money. And to be honest I would ALWAYS go back to the way of conventional wisdom as soon as my ego allowed and my pocket book required!! I no longer "need" to be different and I sure don't need to re-invent the wheel every time out.

Go read and find out what really works, not what YOU want to work and then use it. I seem to have a lot more fun and a lot less stress by doing it this way!
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