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  #1  
Old 12-10-2018, 02:48 PM
Bavafa Bavafa is offline
 
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Default IO-390 fuel flow rate

Just curious what others see for their high end fuel flow, lets say full power at see level?

Yesterday, I saw 20.x GPH on take off at see level which caused my set alarm on G3X to go off. Is that too high for this engine?

I am still dialing in my fuel flow rate and calibration and it might not be super accurate but it is not off by a whole lot.
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  #2  
Old 12-10-2018, 03:06 PM
flynwest flynwest is offline
 
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Default Fuel Flow

That sound right 20 to 21 gph. Reset the limits.
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  #3  
Old 12-10-2018, 03:29 PM
Bavafa Bavafa is offline
 
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Default

Thank you guys, appreciate the confirmation.
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  #4  
Old 12-10-2018, 04:45 PM
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If it was a particularly cold morning, you will see higher fuel flow due to denser air.
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  #5  
Old 12-10-2018, 08:24 PM
N49ex N49ex is offline
 
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Location: Wheaton, Illinois
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Agree. Mine runs about 19.5 to 19.7 and I am at 750 ft. above sea level. Unfortunately, Lycoming is not very clear on this, but I convinced myself of what was appropriate from the published Continental numbers. You can look up the 210 horse 360 or scale from one of the other engines, and you will be in this 19.7 to 20.x range.
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  #6  
Old 12-11-2018, 06:43 PM
spannbauer spannbauer is offline
 
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I work as an engine performance development engineer for a major automotive OEM. Even with all of our fancy equipment it is still good to know the old rule of thumb.

In general I use '1/2 pound of fuel per horsepower per hour' or (0.5 lbs fuel)/(1 hp * 1 hour).

Using that you'll get: 210 hp * (0.5 lbs fuel)/(1 hp * 1 hour) = 105 lbs fuel per hour. The density of gasoline is approximately 6 lbs per gallon, so you're left with an approximation of 17.5 gallons per hour. Given the antique design of these engines it isn't surprising that your value would come in at least 10% over this rule of thumb since the efficiency is so much worse than modern engines. Additionally, you're probably operating rich which would shift the guess.

The point of all of this rambeling is that you can get a quick mental conversion between horsepower and fuel flow with one simple number. If you divide your horsepower by 12, you'll have your approximate GPH fuel flow. If you multiply your fuel flow (in GPH) by 12, you'll have your approximate horsepower output. It's not exact science, but it's something you can quickly do in order to sanity-check against your instruments. Obviously, don't be dumb try to cut your fuel minimums too close using approximations
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  #7  
Old 12-11-2018, 07:14 PM
mturnerb mturnerb is online now
 
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Quote:
Originally Posted by spannbauer View Post
I work as an engine performance development engineer for a major automotive OEM. Even with all of our fancy equipment it is still good to know the old rule of thumb.

In general I use '1/2 pound of fuel per horsepower per hour' or (0.5 lbs fuel)/(1 hp * 1 hour).

Using that you'll get: 210 hp * (0.5 lbs fuel)/(1 hp * 1 hour) = 105 lbs fuel per hour. The density of gasoline is approximately 6 lbs per gallon, so you're left with an approximation of 17.5 gallons per hour. Given the antique design of these engines it isn't surprising that your value would come in at least 10% over this rule of thumb since the efficiency is so much worse than modern engines. Additionally, you're probably operating rich which would shift the guess.

The point of all of this rambeling is that you can get a quick mental conversion between horsepower and fuel flow with one simple number. If you divide your horsepower by 12, you'll have your approximate GPH fuel flow. If you multiply your fuel flow (in GPH) by 12, you'll have your approximate horsepower output. It's not exact science, but it's something you can quickly do in order to sanity-check against your instruments. Obviously, don't be dumb try to cut your fuel minimums too close using approximations
At the advanced engine management course taught by the GAMI gurus, the rule of thumb for LOP (lean of peak) is 14.9 x fuel flow in GPH = HP, and of course you can divide that by rated HP to get a percentage power. For an IO-390 (210HP), for example 10GPH x 14.9 =149 HP, or 71% power. As you noted, aircraft engines are deliberately run rich in climb to lower EGT/CHTs, and the calculation isn't applicable.

I took the course when flying a Bonanza: Continental recommends peak fuel flow at full throttle, full rich for the IO-520 to be around 24GPH: the instructors at the APS course recommended increasing this to 27GPH to improve cooling in climb - higher fuel flow (i.e. running richer) is useful to reduce CHT. You can always lean in climb - the same course recommends leaning to maintain EGT seen at ideal fuel flows at takeoff: usually starting around 3000 AGL and adjusting every 2-3 thousand after that, then stay out of the red box in cruise (either ROP or LOP).

Red box reference: https://www.jpinstruments.com/wp-con...BoxRed-Fin.pdf
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Last edited by mturnerb : 12-12-2018 at 05:42 AM.
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  #8  
Old 12-11-2018, 08:22 PM
Don E Don E is offline
 
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Default Checked my data logs...

My field elevation is 436í and my WOT takeoff fuel flows range from 17.9 to 18.4 GPH. Thatís a stock 390 with stock injectors.
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  #9  
Old 12-11-2018, 10:40 PM
n982sx n982sx is offline
 
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My real world numbers from today. Field elevation 810'

Density altitude -500'

Fuel flow WOT full rich 19 gph max during initial climb.

19.3 gph is highest I've ever recorded in cool weather.
Summer numbers range from 17.5 to 18.5 approx.

Stock io390 in my 14.
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  #10  
Old 12-12-2018, 05:39 AM
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DanH DanH is online now
 
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Quote:
Originally Posted by spannbauer View Post
I work as an engine performance development engineer for a major automotive OEM.
I am darn glad you have joined us.

Quote:
Even with all of our fancy equipment it is still good to know the old rule of thumb.
In general I use '1/2 pound of fuel per horsepower per hour' or (0.5 lbs fuel)/(1 hp * 1 hour).
Using that you'll get: 210 hp * (0.5 lbs fuel)/(1 hp * 1 hour) = 105 lbs fuel per hour.
...which is exactly what Lycoming lists as minimum fuel flow for rated power.
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