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Old Oct 03, 2006, 05:45 AM
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Fuel injected gasoline engine for UAV

Hi all,
This is my first thread so be kind! Im a final year engineering student, and I am a member of a team designing a long endurance, low altitude UAV. I have been given the task of engine selection and integration, however am finding it difficult to find any "off the shelf" fuel injected gasoline engines of the power range we are looking at (around 2.6 KW or 3.5 HP). Would any body know of any engine manufactururs that make fuel injected gasoline engines of this power range - I am aware a few companies that modify existing glow engines, and even some that have modified glow to diesel - but as a reference design I would like to find a company that actually makes the fuel injected gasoline engines.

Any help would be greately appreciated!

Cheers
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Old Oct 03, 2006, 06:13 PM
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kd7ost's Avatar
Nampa. Idaho
Joined Nov 2004
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Quote:
Originally Posted by charlieandrews
Hi all,
This is my first thread so be kind! Im a final year engineering student, and I am a member of a team designing a long endurance, low altitude UAV. I have been given the task of engine selection and integration, however am finding it difficult to find any "off the shelf" fuel injected gasoline engines of the power range we are looking at (around 2.6 KW or 3.5 HP). Would any body know of any engine manufactururs that make fuel injected gasoline engines of this power range - I am aware a few companies that modify existing glow engines, and even some that have modified glow to diesel - but as a reference design I would like to find a company that actually makes the fuel injected gasoline engines.

Any help would be greately appreciated!

Cheers
I'm not aware of any off the shelf versions either. Futaba and OS colaborated on a Glow engine with EFI but that doesn't spell economy. I do know that Aerosonde uses a fuel injected system on their gas powered UAV's but they did tell me it was a closely guarded secret and one of the most difficult things they had to work out in a 1.5 cid engine. They do get about 24 hours or better of flight time on a gallon and a half of 2 cycle gas mix.

Here's a thread that might interest you. Check out what is said from post 31 on. It might be of help. Let us know what you come up with. It's a good topic.

Dan

http://www.rcgroups.com/forums/showt...=long+duration
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Old Oct 04, 2006, 01:02 AM
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I'll second what Dan said. The only stuff I've heard of is the pretty-much-secret magickry the Aerosonde guys did with fuel injection on their Enya (I believe it was an Enya to start with). This is indeed a good topic and an enterprising engineering student is just the thing we need around here, to do some studies on low-consumption engines!

Luke
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Old Oct 04, 2006, 06:29 AM
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Maynard Hill's TAM-5 used a modified carb to get 2 oz per hour consumption on a .61 4 stroke.

http://findarticles.com/p/articles/m...01/ai_n9400487
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Old Oct 04, 2006, 09:30 AM
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Yeah I have done a little resarch into both the Aerosonde and ScanEagle aircraft. The Aerosonde team used a HEAVILY modified ENYA R120 (in there first design anyway - I believe the crank casing is the only remaining component). They also use a seperate oil system, with oil fed to the engine through positive crankcase ventilation - removing the need to dilute the fuel with oil! The ScanEagle (the base design for the UAV we are looking at) uses a modified 3W engine - lots of protected secrets though!
I'll just have to have a look around, I know alote of people have done alote of things with regards to engine mods, its just difficult doing any kind of theoretical analysis because the numbers arn't out there (BSFC's etc).

Thanks for the replies though guys, much appreciated!
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Old Oct 04, 2006, 09:42 AM
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United States, TX, Wimberley
Joined Mar 2004
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Hey Charlie,

You may want to look into some of the aftermarket EFI systems that are used in setting up turbochargers on automobiles.. Many guys will take an engine that is not normally turboed and do a DIY setup.. the trick is getting extra fuel into the engine if your stock computer doesnt allow for you to increase fuel curves and injector pulse.
There are aftermarket single injector systems that would basically tie into your existing sensors to regulate a single injector that provides fuel under boost..
There is a computer like that made by Halltech that is desigend to run an EFI system from 1 to 8 cylinders. I know the engine our working with is small and there may be too much of a weight penalty but that is all part of the challenge..

A while back there was a video circulating around the internet of a guy on one of those small gas powered scooters racing a hopped up Trans AM WS6(345hp)
The single cylider scooter had a small turbo on it.. Scarry thing was that it was just as fast as the TA!

Myron
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Old Oct 24, 2006, 07:51 PM
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Chicago
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And another thing to keep in mind - carburetor can be tuned to a perfect mixture on a steady power setting (as would be on uav) , and probably provide better efficiency than a crude half component injection system ever could. At a fraction of a cost.
Same is true for ignition - when run at preset optimum rpm there is no need to have variable timing.
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Old Oct 24, 2006, 09:25 PM
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Minnesota
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Quote:
Originally Posted by Tom Harper
Maynard Hill's TAM-5 used a modified carb to get 2 oz per hour consumption on a .61 4 stroke.

http://findarticles.com/p/articles/m...01/ai_n9400487
That's amazing. The OS 1.60FX on my Rascal 110 UAV burns about 2 oz per minute at full throttle (maybe closer to 1 oz per minute in normal flying.) The OS .61 4 stroke on my Kadet Sr. probably burns 1 oz every 2-4 minutes depending on throttle setting ... and to get across the Atlantic, you can't be running your throttle on idle the whole way.

Those guys certainly did a nice bit of engineering to pull that all together.
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Old Oct 24, 2006, 09:34 PM
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Maynard built engines and carbs for perhaps 40 to 50 years before his transatlantic flight. He holds many model plane records for endurance and high altitudes.

His OS .61 FS was modified for spark ignition and the generator charged batteries to keep the ignition powered. The carb had a much smaller than stock venturi and he used miserly amounts of white camp stove gas as fuel. Some type of kitchen cooking oil was used as a lube. Vegetable or animal based I don't know which. His fuel mix burned really hot. The engine had lost power to gain that endurance but was plenty strong to get it across the Ocean in fair weather.

Dan
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Old Oct 24, 2006, 09:36 PM
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Hi cholson,

Yes it was certainly some impressive engineering! But bear in mind they converted their .61 4-stroke to run on gasoline with spark ignition, and with a tiny carb. I think they ran it at something like 3900 RPM across the Atlantic, so they were virtually idleing it!

Hugo
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Old Oct 27, 2006, 03:46 PM
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Thoughts on fuel useage

A well made 2 stroke (weedeater type) with proper leaning of the mixture and work on optimizing the gas to oil ratio (if you aren't trying for max output the oil requirements go down) and proper cooling (to compensate for lower oil ratios), tweak the timing for the optimum at you rpm and you should be able to get good performance.

run as large a prop as practical

On the other hand if you wnat lots of speed...
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Old Oct 27, 2006, 10:21 PM
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Thats Funny. It is a million dollar question. If you find an answer, call me immediately.
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Old Oct 27, 2006, 10:39 PM
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Miami
Joined Apr 2005
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Quote:
Originally Posted by charlieandrews
Hi all,
however am finding it difficult to find any "off the shelf" fuel injected gasoline engines of the power range we are looking at (around 2.6 KW or 3.5 HP). Would any body know of any engine manufactururs that make fuel injected gasoline engines of this power range

Cheers
Forget fuel injection, its abslutely NOT NEEDED. Get a Zenoah G-45. Mine is VERY reliable, light, has the power you are looking for, and has flown over 2000 miles without a single failure and zero maintenance, I have never even had the plug out It is self contained, no ignition battery or any extra stuff to worry about, I just start it and fly, never even have to think about the engine.

If you want 4 stroke reliability and efficiency, then get the Honda 32 CC weed eater conversion. Less power, but is reliable, great fuel usage, and also self contained. No ignition battery etc. to worry about.

If you start trying to make your own EFI, or converting glow engines, you are going to complicate matters, make it 10 times as hard as it needs to be, and end up with an unreliable engine.

The solution to your needs is available, cheap (400 dollars) and you wont waste a bunch of time on something that wont work. Dont make your project harder than it needs to be.

JettPilot
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Old Oct 27, 2006, 11:07 PM
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Jett, part of his requirement was long-distance/endurance (ie, fuel miserly). What can you tell us about the fuel consumption of the Zenoah and Honda engines you mentioned?

Luke
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Old Oct 28, 2006, 12:05 AM
JettPilot's Avatar
Miami
Joined Apr 2005
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Fuel injection is NOT needed for fuel efficiency.

If he is looking for the most efficient engine, then the Honda 32 CC 4 cycle engine would be the way to go. Its very fuel efficient.

JettPilot
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