Max Fuel Tank Size?
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Max Fuel Tank Size?
Ordered a Magnum .91 4-stroke this afternoon and was reading the manual that's available on line. In the section on fuel tank selection they make the following statement:
The size of the fuel tank used should be 12oz. - 14oz., depending on the
model and the length of flights desired. Use of a 14oz. tank will provide
between 10 - 15 minutes of run time at full throttle. Use of a fuel tank any
larger than 14oz. can lead to excessive leaning of the engine during flight
and is not recommended.
Trying to think this through, the only thing I can come up with is that the engine may not be able to draw fuel correctly from a nearly empty fuel tank whose volume is larger than 14 oz. Am I on the right track? I tend to fly very conservative, usually land after about 9 to 10 minutes, and normally with at least 1/4 tank of fuel left. Would the 14 oz. limit still hold true in this case?
The size of the fuel tank used should be 12oz. - 14oz., depending on the
model and the length of flights desired. Use of a 14oz. tank will provide
between 10 - 15 minutes of run time at full throttle. Use of a fuel tank any
larger than 14oz. can lead to excessive leaning of the engine during flight
and is not recommended.
Trying to think this through, the only thing I can come up with is that the engine may not be able to draw fuel correctly from a nearly empty fuel tank whose volume is larger than 14 oz. Am I on the right track? I tend to fly very conservative, usually land after about 9 to 10 minutes, and normally with at least 1/4 tank of fuel left. Would the 14 oz. limit still hold true in this case?
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RE: Max Fuel Tank Size?
Just my guess but with more than a 14 oz tank centered on the carb., when the fuel gets low, it will be harder to pull fuel up from the bottom of the tank. It would be like having the tank too low.
#3
RE: Max Fuel Tank Size?
Actually its the length that is the problem. Flying straight up on a nearly empty tank will be the leanest part of a typical run. The larger tanks are usually longer and will make this worse. Uniflow tank setup will not improve this, if you need a larger tank recommend a pump or regulator.
#4
RE: Max Fuel Tank Size?
Yes as Sport Pilot stated it is the length of the fuel line from the tip of the clunk to the carb on the engine.
The longer the fuel line the harder it is for the engine to draw fuel properly. So you wind up running the engine more rich to compensate, which may result in too much of a power loss at the beginning of the flight. But after the fuel tank gets down to around 1/2 full, then the engine leans out more and getting more lean as the tank empties.
The longer the fuel line the harder it is for the engine to draw fuel properly. So you wind up running the engine more rich to compensate, which may result in too much of a power loss at the beginning of the flight. But after the fuel tank gets down to around 1/2 full, then the engine leans out more and getting more lean as the tank empties.
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RE: Max Fuel Tank Size?
H, fourstrokes typically use about 1 oz of fuel per minute per cu in displacement. A 12oz tank will be plenty for a 10-12 minute flight. I used to get all enthusiastic and cram the largest tank that would fit and after the last flight I'd end up pumping half a tank back into the jug.
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RE: Max Fuel Tank Size?
Thanks for the input guys. I guess in this age of the ARF, sometimes it's hard (if not impossible) to control the fuel tank size/shape. I have a couple of Hanger 9 ARF planes. A Toledo Special, fuel tank on that one is only 11 oz. and I have a Saito 62 on it, so I'm safe there. The other one, a Pulse 60 XT comes with a "shaped" 17 oz. fuel tank that fits like a glove into a "egg shaped" space under the front hatch. There's nothing available from any of the fuel tank folks that will fit that space. Possibly, all I should do is open the tank up and shorten the fuel intake line. Or maby better yet, do nothing. There's a lot of these Pulse 60 XTs out there and I may be the only one in search of an issue to solve. It's the engineer in me. Just can't leave well enough alone.
#7
RE: Max Fuel Tank Size?
ORIGINAL: Homer712
Thanks for the input guys. I guess in this age of the ARF, sometimes it's hard (if not impossible) to control the fuel tank size/shape. I have a couple of Hanger 9 ARF planes. A Toledo Special, fuel tank on that one is only 11 oz. and I have a Saito 62 on it, so I'm safe there. The other one, a Pulse 60 XT comes with a ''shaped'' 17 oz. fuel tank that fits like a glove into a ''egg shaped'' space under the front hatch. There's nothing available from any of the fuel tank folks that will fit that space. Possibly, all I should do is open the tank up and shorten the fuel intake line. Or maby better yet, do nothing. There's a lot of these Pulse 60 XTs out there and I may be the only one in search of an issue to solve. It's the engineer in me. Just can't leave well enough alone.
Thanks for the input guys. I guess in this age of the ARF, sometimes it's hard (if not impossible) to control the fuel tank size/shape. I have a couple of Hanger 9 ARF planes. A Toledo Special, fuel tank on that one is only 11 oz. and I have a Saito 62 on it, so I'm safe there. The other one, a Pulse 60 XT comes with a ''shaped'' 17 oz. fuel tank that fits like a glove into a ''egg shaped'' space under the front hatch. There's nothing available from any of the fuel tank folks that will fit that space. Possibly, all I should do is open the tank up and shorten the fuel intake line. Or maby better yet, do nothing. There's a lot of these Pulse 60 XTs out there and I may be the only one in search of an issue to solve. It's the engineer in me. Just can't leave well enough alone.
#8
RE: Max Fuel Tank Size?
Sorry for the duplicate post here... My cat decided to try her paw at posting on RCU... Instead she copied what I wrote.. go figure... [:-]
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RE: Max Fuel Tank Size?
1Q, fourstrokes run regulators very well, here's a Saito 1.30 with two Cline regulators, since the check valve captures the peaks of the power pulses there is plenty of pressure. In fact there is enough to put a serious bulge in a stiff walled Sullivan tank.
#11
RE: Max Fuel Tank Size?
ORIGINAL: Hobbsy
1Q, fourstrokes run regulators very well, here's a Saito 1.30 with two Cline regulators, since the check valve captures the peaks of the power pulses there is plenty of pressure. In fact there is enough to put a serious bulge in a stiff walled Sullivan tank.
1Q, fourstrokes run regulators very well, here's a Saito 1.30 with two Cline regulators, since the check valve captures the peaks of the power pulses there is plenty of pressure. In fact there is enough to put a serious bulge in a stiff walled Sullivan tank.
I stand by my thought that shortening the fuel pickup line is not going to cure the trouble of an engine running over-lean at the bottom of too big of fuel tank... If one uses a felt clunk in the tank, that will cause even more problems on bigger engines. My SuperTigre S90K will not run anywhere close to rich enough using a felt clunk, even on a 4oz tank. I normally use a 16oz tank on this engine which the engine can drain in about 10-12 minutes at WOT using a normal clunk.
#12
RE: Max Fuel Tank Size?
ORIGINAL: Homer712
Thanks for the input guys. I guess in this age of the ARF, sometimes it's hard (if not impossible) to control the fuel tank size/shape. I have a couple of Hanger 9 ARF planes. A Toledo Special, fuel tank on that one is only 11 oz. and I have a Saito 62 on it, so I'm safe there. The other one, a Pulse 60 XT comes with a "shaped" 17 oz. fuel tank that fits like a glove into a "egg shaped" space under the front hatch. There's nothing available from any of the fuel tank folks that will fit that space. Possibly, all I should do is open the tank up and shorten the fuel intake line. Or maby better yet, do nothing. There's a lot of these Pulse 60 XTs out there and I may be the only one in search of an issue to solve. It's the engineer in me. Just can't leave well enough alone.
Thanks for the input guys. I guess in this age of the ARF, sometimes it's hard (if not impossible) to control the fuel tank size/shape. I have a couple of Hanger 9 ARF planes. A Toledo Special, fuel tank on that one is only 11 oz. and I have a Saito 62 on it, so I'm safe there. The other one, a Pulse 60 XT comes with a "shaped" 17 oz. fuel tank that fits like a glove into a "egg shaped" space under the front hatch. There's nothing available from any of the fuel tank folks that will fit that space. Possibly, all I should do is open the tank up and shorten the fuel intake line. Or maby better yet, do nothing. There's a lot of these Pulse 60 XTs out there and I may be the only one in search of an issue to solve. It's the engineer in me. Just can't leave well enough alone.
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RE: Max Fuel Tank Size?
ORIGINAL: DaveFri
Sorry ..not hijack the thread but....if you had a 120 4-stroke...then how much flite time could one expect from a 12-14 oz tank...approximately..??
Sorry ..not hijack the thread but....if you had a 120 4-stroke...then how much flite time could one expect from a 12-14 oz tank...approximately..??
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RE: Max Fuel Tank Size?
My brother and I use a lot of .91 four strokes. We typically use 10 to 12 ounce tanks. We set the timer for 10 minutes and land shortly after it beeps. We never run out of fuel and are not carrying a lot of excess fuel weight around.