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Fuel Burn question

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Streffpilot

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Hello, I have no experience with aviation use of 2 strokes......The weight savings peaked my interest for my Minimax.....

I am curious about different fuel burns at cruise (70% power) for different hp......


50 hp
60 hp
70 hp

Or any other hp you might have experience with.

I just dont know what to expect........Thank you ahead of time for your help
 

Aerowerx

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I don't know about 2 strokes, but for 4 strokes the rule of thumb is about 6 gallons per hour for every 100 hp.

So a 40 hp engine would burn 2.4 gallons per hour.
 

nickjaxe

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I have a Rotax 503 50hp duel carb 2 cylinder 2 stroke...in my 50mph draggy a/c at cruise power 5000RPM it burns 10 LPH solo....2 up it burns 15LPH.

Hope thats of some help.

Nick.
 

radfordc

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My Rotax 503 turns 6000 rpm to keep my airplane flying and burns a little less than 4 gal/hr.
 

radfordc

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I have one of the biggest 1/2 vw engine Hummel makes. Its rated at around 45 hp. I burn a little over 1 gallon an Hr.
At full power? That would be .13 lb/hr/hp SFC. Most normally aspirated engines are around .5 lb/hr/hp. I assume you meant 1 gal/hr at low cruise power.
 
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don january

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how can a person even get a number? you have head wind's, grass strip, paved strip. I don't think you can get a true number.
 

Joe Fisher

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I think 1/2 lb/hour /horse power. One gallon / hour is 12 horse power. My Cub with 65 cont. 4 gallons/hour 48hp. 70% of 65 =45.5. My Colt with 108 Lyc. 6 gallons/hour. 70% of 108= 75.6=6.3 gallons/hour. That is what I see in my real world.
 

Aerowerx

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how can a person even get a number? you have head wind's, grass strip, paved strip. I don't think you can get a true number.
With a clock and a fuel gauge. Use X gallons of fuel in Y minutes, at a constant RPM. The fuel usage would be X/Y. All that other stuff is irrelevant until you start talking about airspeed or takeoff roll.
 

N8053H

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At full power? That would be .13 lb/hr/hp SFC. Most normally aspirated engines are around .5 lb/hr/hp. I assume you meant 1 gal/hr at low cruise power.
I meant I go out, fuel up my airplane and go fly for an hr. I land and refuel. I put a little over 1 gallon back in the fuel tank. Those are real world numbers. You can crunch the numbers all day on paper, put what counts is what one actually uses in real life not what should be used when doing the math on paper. I guess if I flew around at WOT I may burn over 2 gallons an hr. But this is no turbine. Meaning it does not run at 100% power settings.
 

N8053H

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To give a more accurate description. After I level off or climb out, I set the MP gauge to around 23. With an RPM of around 2800. On climb out I see close to 3200 rpm. I try to keep the MP under 25 in cruise. Anything between 21-23 is the ideal spot or what I like to cruise at.

Tony
 

nickjaxe

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Used to be a guy at my airfield...operated a older mini-max...that had an older Rotax 447...think they are around 40hp...seemed to go well with that...quite a light motor.
 

Pops

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Friend of mine had over a thousand hours on a larger 1/2 VW engine in a Mini-Max and I told him anytime he makes the hour flight to my field, I will fill him up for free. Usually took 1.7 gallons of fuel to top him off.
 

BJC

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Friend of mine had over a thousand hours on a larger 1/2 VW engine in a Mini-Max and I told him anytime he makes the hour flight to my field, I will fill him up for free. Usually took 1.7 gallons of fuel to top him off.

Hoping that your field isn't flooded ...


BJC
 

Pops

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Hoping that your field isn't flooded ...


BJC
He lives in the flood areas but on higher ground and I am north of the worse part. Watched the storms all night. The lighting was so bad that it was continuous light outside. No way you could sleep.
 
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N8053H

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Friend of mine had over a thousand hours on a larger 1/2 VW engine in a Mini-Max and I told him anytime he makes the hour flight to my field, I will fill him up for free. Usually took 1.7 gallons of fuel to top him off.

What one finds should work on paper, in the real world, it does not always compute like it does on paper. Fuel burn according to HP rating is a good example of this.
 

mcrae0104

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What one finds should work on paper, in the real world, it does not always compute like it does on paper. Fuel burn according to HP rating is a good example of this.
No one gets an exemption on the laws of chemistry and physics. If "real world" numbers don't match fairly closely with what is expected based on a hundred years experience with internal combustion engines, it seems more likely that there is some imprecise measurement going on rather than all of the other evidence being disproven.

Don't get me wrong, Tony; I'm not saying the results you see aren't happening or that you're stretching the numbers. It's just that there's room for error when the numbers are so small. "About an hour" and "about a gallon" are different in everyday use than in a laboratory.
 
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