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  #11  
Old 08-01-2012, 10:51 PM
flynwest flynwest is offline
 
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Location: Sacramento
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Smile Take off fuel burn

On my IO 390X RV 8 fuel injected I see 20.3 gal. per hour on take off at 45 msl.
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  #12  
Old 08-01-2012, 11:35 PM
Lars Lars is offline
 
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Location: Davis, CA
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Quote:
Originally Posted by RV10inOz View Post
You have something not right, either fuel flow measurement or your fuel flow.

One or the other. Either way get it fixed.

18GPH please +/- 0.5 GPH is the aim. If it gets to 5% you need to tweak.
That works out to 0.6 pounds/HP-hour for a 180 HP engine assuming avgas at 6 pounds per gallon. Is that based on a rule of thumb, empirical data or Lycoming data or something else?
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  #13  
Old 08-02-2012, 04:34 AM
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RV10inOz RV10inOz is offline
 
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It is from demonstrated data.

Oddly enough, from the factory my IO540 and most others achieve this.

It is a rule of thumb, however ths rule is in keeping with well established data. Oddly enough TCM recently have found themselves releasing SB's.

You can bank this rule of thumb, it is not an OWT
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  #14  
Old 08-02-2012, 05:42 AM
David-aviator David-aviator is offline
 
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With a fixed pitch prop turning 2100-2200 for take off, the engine is not developing anywhere near 180 HP, it 's more like 135 HP. At that power level the fuel flow is about right.

What is the fuel flow at WOT in flight where the rpm is nearer 2700 and the engine is developing more like 180 HP?
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  #15  
Old 08-02-2012, 01:15 PM
Lars Lars is offline
 
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Quote:
Originally Posted by RV10inOz View Post
It is from demonstrated data.

Oddly enough, from the factory my IO540 and most others achieve this.

It is a rule of thumb, however ths rule is in keeping with well established data. Oddly enough TCM recently have found themselves releasing SB's.

You can bank this rule of thumb, it is not an OWT
It seems high to me, but then I don't have any data immediately available (and couldn't find any with a quick search) showing specific fuel consumption at wide open throttle, and presumably full rich mixture. I'm accustomed to seeing and using 0.5 lb/hp-hr for calculations, but maybe that's closer to stoichiometric? In any case, using 0.5 translates to 15 gph, which is closer to what some here have observed. Too lean on takeoff?
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  #16  
Old 08-02-2012, 03:40 PM
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mannanj mannanj is offline
 
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Default Fuel Flow

To add another data point. I have a 200 hp engine with a constant speed prop and at sea level, it will trip my fuel flow alarm (set at 20gph) occasionally on take-off.
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  #17  
Old 08-02-2012, 04:38 PM
N743RV N743RV is offline
 
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Location: Livermore, CA
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Lars,

I agree with you. I think the your value of 0.5 lb/hp-hr is just about right for my IO 360 with the Hartzel blended airfoil prop and Lasar ignition.
Bob Cowan
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  #18  
Old 08-02-2012, 06:08 PM
Scott Hersha Scott Hersha is offline
 
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Location: Cincinnati, OH
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As Dave has said, your takeoff RPM (horsepower) has everything to do with resulting fuel flow. So does what carb you have. JT and I have exactly the same engine (ECI O360 Titan with 9:1 pistons, built by the same engine shop, but with slightly different carbs. mine has a richer power enrichment set-up at full throttle than Jon's and I see up to 20 gph at takeoff (2700 rpm), about 3-4 more than Jon. At cruise at the same airspeed I see a slightly less FF than he does - verified at fill up. I don't think you are seeing anything unusual with your setup. As long as your other engine indications are normal (CHT, EGT, expected power/climb rate for the RPM) you are in good shape.
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  #19  
Old 08-02-2012, 06:34 PM
David-aviator David-aviator is offline
 
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Default .51 is a good number leaned out....

The IO360 I had with the 7A was a Barrett engine and it came off the dyno with a BSFC of .51 lbs/hr/hp. I believe that number was derived at best power mixture.

At take off with mixture full rich the number is higher for sure. If it is .60, the 13.5 gph with a fixed pitch prop computes to 135 HP which is about all that can be expected. RPM is in the 2200 range and the fuel flow is about normal.

It is impossible to develop 180 hp at 2200 rpm with a normally aspirated engine. If fuel flow were 15-16 gph at 2200 rpm, that would be a problem.
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  #20  
Old 08-02-2012, 06:46 PM
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RV10inOz RV10inOz is offline
 
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Folks, the info I have provided already is proven good data.

As some have shown, the IO390x is about 20GPH, funny enough for 200HP engines at 2700 RPM full rich at ISA, thats HP/10

On the rich side of peak EGT the HP is determined by MAss Air Flow, so in rough terms if you have a fixed pitch prop and get 2200 RPM on a ISA day (15deg C and 1013/29.92) you should see 146 HP and a fuel flow around 14-14.5GPH.
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