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HelicopterMain Discussion › Pumped motor vs. non-pumped
09-13-2007 02:40 AM  10 years agoPost 1
Nashville

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Formerly Music City now back home in Sunny Florida

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Ok. Stupid question time. I just bought an OS SZ 91 motor for my Avant. It is pumped. Are there advantages to this? I've always run non-pumped in my 50's. Also, what is the proper setup with the pumped motor? Should it have the fuel tube connected to the muffler or just cap the muffler? Thanks.

I was Spektrum when Spektrum wasn't cool

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09-13-2007 02:48 AM  10 years agoPost 2
Nashville

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I did some searching and got some answers. But more confused than anything. Another question, if using muffler pressure does this use more fuel? Seems like it does.

I was Spektrum when Spektrum wasn't cool

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09-13-2007 02:58 AM  10 years agoPost 3
legoman67

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Nanoose Bay B.C, Canada

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you cap the muffler when using a pumped system. fuel goes from main tank to pump, the to top of header, then to engine....

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09-13-2007 03:04 AM  10 years agoPost 4
Envision

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MI

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fuel goes from main tank to pump, the to top of header, then to engine....
That doesnt sound right. When the pump runs out of fuel the header tank will still be full? Will it still pump with only air? Serious question...

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09-13-2007 03:05 AM  10 years agoPost 5
JeffM1999

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Erie, CO

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A pumped system should be more consistent throughout the tank of fuel. A muffler pressurized system tends to lean out towards the end of the tank.

Pumped systems add a small extra level of complexity to your fuel system, but I have found that they run smoother and are easier to tune. Just make sure your check valve is facing the right direction...

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09-13-2007 03:06 AM  10 years agoPost 6
JeffM1999

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Erie, CO

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That doesnt sound right. When the pump runs out of fuel the header tank will still be full? Will it still pump with only air? Serious question...
I have always run the fuel line from the main tank to the header and then to the pump and lastly the carb. Some say that the header is unnecessary with a pumped system, but I always run one anyway.

EDIT: To clarify, the pressure tap line should run from the backplate through the check valve to the main tank in the scenario that I posted about.

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09-13-2007 03:44 AM  10 years agoPost 7
Nashville

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Thanks guys. Any pics of your setup? That sure would help un-confuse me.

I was Spektrum when Spektrum wasn't cool

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09-13-2007 03:47 AM  10 years agoPost 8
JeffM1999

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Erie, CO

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Here is a pic of my old Freya with a pumped YS91. It is kind of hard to see, but the pressure line goes from the motor backplate, through the check valve, to the main tank. Then the fuel line goes from the main tank, through the header tank, into the carb.

Feel free to PM me if you are still having troubles.

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09-13-2007 03:50 AM  10 years agoPost 9
JeffM1999

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Erie, CO

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remember to have an air vent line off your main tank. Otherwise you will flood your engine everytime after you kill it.

You need to pinch off the fuel line going into the carb and vent the air from the main tank immediately after shut-down, otherwise the air pressure in the main tank will force fuel into the carb/engine.

Hope that makes sense.

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09-13-2007 04:02 AM  10 years agoPost 10
tlankford01

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Amarillo, TX 79110

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I only use ys motors in my nitro setups. This is because of the pump. I still use a header tank. This provides the most consistent setup thorough out the entire tank. As far as carb settings with my ys I only change with the seasons.

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09-13-2007 04:04 AM  10 years agoPost 11
JeffM1999

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Erie, CO

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Here, I tried to use Microsoft paint and show you how it is plumbed. WARNING: I am retarded with photo editing software, view at your own risk.

Sent you a PM also, feel free to call me.
-Jeff

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09-13-2007 04:06 AM  10 years agoPost 12
JeffM1999

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Erie, CO

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wow... after looking at the pic I just posted, I am even more retarded than I thought! LOL!

caption at the bottom says "Backplate Air Pressure into Main Tank"
caption at the top says "Air Vent Line"

Sorry that pic is so horrible. Just give me a call, it will be much easier to explain. I have a 600N, too.

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09-13-2007 04:37 AM  10 years agoPost 13
JeffM1999

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Erie, CO

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fuel goes from main tank to pump, the to top of header, then to engine....
After looking a little closer at the OS91SZ pumped, Legoman is probably right. Fuel would get sucked from the main tank into the pump, then into the header to eliminate bubbles, and then into the carb.

This is a little different from the YS systems that I have had experience with, but after looking at this particular setup a little closer, it sounds logical to me.

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09-13-2007 05:08 AM  10 years agoPost 14
legoman67

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Nanoose Bay B.C, Canada

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hehe, i dont even have a pumped system, but one question that trex600 brought up wiht me in a pm, how does the fuel not pour out the vent when inverted?

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09-13-2007 05:12 AM  10 years agoPost 15
JeffM1999

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Erie, CO

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The vent line would have to be plugged when the motor is running to prevent fuel loss and keep air pressure in the tank, and the air pressure would have to be relieved after each flight to prevent flooding the motor.

That is how the YS systems have worked for me in the past, but I don't have an OS91SZ with the pump to compare it to.

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09-13-2007 05:17 AM  10 years agoPost 16
Nashville

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Formerly Music City now back home in Sunny Florida

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boy would that suck to be inverted and see fuel pouring out! Thanks again Jeff. I'm going to cap the muffler and the tank and see how she does. I hear it will comsume less fuel.

I was Spektrum when Spektrum wasn't cool

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09-13-2007 05:20 AM  10 years agoPost 17
JeffM1999

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Erie, CO

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Best of luck to ya! Let us know how things turn out.

p.s. Great talking to ya! Give me a call anytime!

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09-13-2007 05:26 AM  10 years agoPost 18
Envision

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MI

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After looking a little closer at the OS91SZ pumped, Legoman is probably right. Fuel would get sucked from the main tank into the pump, then into the header to eliminate bubbles, and then into the carb.
But after the main tank is empty would the pump still supply air pressure to the header so it would run until the header is empty? Or would it run out of fuel with the header still full since the pump has nothing to push?

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09-13-2007 05:45 AM  10 years agoPost 19
DrDan

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Potosi, Missouri

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If the main tank is not pressurized, you don't have to plug the vent. The pump is pulling the fuel out of the tank which is then in turn filling with air that is being pulled in through the vent. If the tank is pressurized, then yes you would have to plug the vent.

I am just throwing this scenerio out there because a lot of folks are using it like this and getting better results. I also have the pumped version.

Dr. Dan

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09-13-2007 02:55 PM  10 years agoPost 20
gullie667

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Brooklyn, NY

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You get more power from a non pumped engine.
You get a more consistent run from a pumped engine.

A friend of mine runs an Os 91 SZ-H w/o pump and it runs well. He says the only fuel it really likes is Wildcat 30% CY though. That is the fuel I use so I am fine with that...

I have a Vibe w/ an OS 91 sz-h and a Cline mod but no header tank and it runs really consistent too.

I bought the os 91 sz-h w/o pump for my Aurora.

Gullie

Helicopters - 1000 parts flying in formation.

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HelicopterMain Discussion › Pumped motor vs. non-pumped
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