topwinguk

Hi

Anyone tell me what the specific fuel consumption is between glow and gas engines of similar size?

Tony

pe reivers

2:1

krayzc-RCU

My Feedback: (31)

I fly the following gas motors on:

3w-150 40oz tank easy 12 minute flight
3w-150 50 oz tank easy 15 min flight
DA85 24 oz tank easy 12 min flight
Brison 3.2 = 52.5 cc 16 oz tank easy 14 min flight

All of the above planes are at about 1/4 of a tank when I land if I fly lots of IMAC/sport flying
If I do only 3d they are all at 1/2 tank to 3/4 tank left when I land....
Most engine makers will tell you what about of fuel their motors use a certain RPM this is what Desert Aircraft says:

For their 170cc motor Fuel Consumption: 4 oz/min @ 6,000 RPM
For their 150cc motor Fuel Consumption: 3.3 oz/min @ 6,000 RPM
For their 100cc motor Fuel Consumption: 2.5 oz/min @ 6,000 RPM
For their 85cc motor Fuel Consumption: 2.2 oz/min @ 6,000 RPM

these are all large gas motors now take the DL20 and 30 and those babies sip about 1/2 oz or less a minute now that is the ticket gas all the way

WCB

I ran 18-24 ounce tanks with a Saito 150 and 12 ounce tank for a 26cc Zenoah gas (which is close power wise). The Saito would use about 14 ounces in a 10 min. flight. The Zenoah about half that. So Pe is pretty accurate at 2:1.

pe reivers

It is the rule of thumb.
A second rule is, that a gas engine uses it's displacement per minute at full throttle. Only half of that displacement at normal flying.

Tired Old Man

My Feedback: (1)

Then you have set up methodology.

Are you jetting for power or duration? Weight and altitude? Specific fuel consumptions can vary greatly between engines of the same type, completely dependant on intentional carb and jet sizing. Then you have the variations induced by an engine manufacturer using different models of carbs on the same engine.

Short version is go with Pe's answer of 2-1 of more glow fuel than gas, and displacement/minute at full throttle. Makes life a lot simpler that way.

STUKA BARRY

Yeah... what he said.

Whistling Death

That is true because I changed from glow to gas in my GP RV-4 but I kept the same tank. Now I get twice as much flying time as I used to.

pe reivers

You know I will be jetting for power, not duration. Power tuning is up to 40% rich! Altitude will need even more leaning of the mixture, so my thumb's rule goes down the drain! However, I like your last lines!
PS,
on a personal note: finally succeeded in obtaining the original Aspen oil, and will send you a sample of three oils, including the Aspen. I will know wich is wich, you won't. My treat, our gain.