Hi guys,

What should be the expected fuel flow from a 20CC gasser engine (say, a G20Ei with a 15X6 prop) in mild cruise, non-aerobatic flight? IOW, how long should I expect a 16oz tank to last?

Also... can anyone share thrust data from the above prop at full power in an engine such as the G20Ei?

Thanks,
Bruno

I would say that if you were to drink 16oz of water immediately before takeoff with that setup, your flight time would be limited, not by how long the fuel lasted, but how long you'd go before you had to land for a "pit stop"
Seriously, 16oz for a 20cc engine will go a long, long time. I have a 20cc engine (RCGF) in an old Extra 300, I fly at WOT much of the time. The fuel tank is only 10oz and my flight timer is set at 12 Min. and there's plenty left in the tank after that 12 min. flight.
Pete

OK, I see you're in Brazil. What percentage of Ethanol will you be running. I run the standard 87 octane 10% ethanol blend sold in my area

I have a well broken in G20ei on my RV4 with a 16oz tank and after a 15min flight I still have over a half tank of fuel left . Most of the flight time is WOT.
The thrust you get will depend on the brand and type of the prop as much as the size of the prop. So asking for thrust based only on the size is pretty much meaningless.

Thanks for the replies, guys.

Since this will be far from WOT, it seems safe to assume 15-30min endurance on a 16oz tank. This project is for an autonomous UAV, and if more endurance should be needed, the fuel tank may always be replaced by a slightly larger one.

Pilotpete2 - Auto fuel in Brazil has a high ethanol content - it has recently been reduced to 20%, from the earlier 25% mix. I'd rather use straight gasoline, but it just isn't available here. We don't have Coleman fuel, either, so I'm pretty much stuck with this 20% mix (or use AVGAS). I have extracted ethanol from auto fuel in the past, and don't want to go through the process again.

I'll keep the forum posted with my progress with this.

On a dle20 with a 14 oz tank I flew 15 minutes and still had half a tank, and thats with an APC 16x8 prop, mostly WOT.  It also depends on how light the wing loading is. If the plane can hover at 1/8th throttle without stalling, chances are you can fly even longer.  My 4*120 will stall out at that speed, a touch over 1/4 is where mine is at.

Funny thing is, between 1/2 and WOT there is not much difference in RPMs! 

The static thrust on the G20 is way less than the DLE20, but not sure what the absolute number. I own both of them and the DLE20 is much stronger and lower weight. Zenoah is probably better long term engine, though.

As far as fuel, 8-10 ounce tank is adequate for either, any more is overkill for a 15 minute flight.

What numbers do you have? I fly the G20, and it's an impressive engine. My DLE 20 is still in the box, so I have not yet compared them.