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Topic-icon Arrow 200 take off fuel flow

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5 months 11 hours ago #1273

hi

I see about 16gph fuel flow on my arrow 100 at sea level take off power. strangely this puts me at just about only 75 F rich of peak (1400-1450F egt during take off).

is there a way to increase the take off power fuel flow? what got do you all see on your arrow 200?

Baris

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4 months 4 weeks ago #1274

Hi Baris;
Great question. Let's take a look at some statistics about the systems involved.
I took a look at the Lycoming IO-360 Operators manual for some of this information.
Figure 3.5 in the manual cites a fuel consumption at 200 hp of 93.5 pounds per hour. 93.5 divided by 6 which represents the weight of a gallon of 100 LL avgas at average temperature yields a fuel power fuel flow of 15.58 gallons per hour.
Based on the data from the performance charts published by Lycoming, you are getting a little more than full power fuel flow at takeoff.
You quote a number of 16 gph fuel flow at takeoff. I'm going to assume that you're getting that number from a fuel flow gauge. If your fuel flow gauge is an aftermarket stand-alone gauge or is part of an aftermarket engine monitor such as the ones from Electronics International or JP Instruments, the fuel flow gph reading will be correct IF what's called the K-factor has been properly set during the installation of the gauge. You can verify the correctness of the K factor by filling your tanks to a recognizable spot on the filler neck, for instance. Then after taking off on one tank (we will call this tank 1) and climbing to altitude (any one you're comfortable with for leaning.) After leveling off, lean the engine in accordance with your normal practice at your normal cruise power setting. Then note the time and switch to the other fuel tank (tank 2). Fly without touching the throttle or mixture knobs or climbing or descending for an hour. Note the fuel flow gauge gph reading during the flight. At the end of exactly one hour, switch from tank 2 back to tank 1 and return to base. When fueling tank 2 the amount of the fill should match the fuel flow gauge gph setting. If it doesn't, you need to adjust the K-factor setting. It's usually pretty easy. Continue to adjust until you're within a few tenths of a gallon per hour.
Cylinder head temperatures (CHT) are the most important number during high power operations. EGT numbers are used to establish peak EGT when leaning at 75 percent or lower. Due to many variables such as installation orientation and distance from the cylinder exhaust flange, the actual numerical value of EGTs is not important.
If your CHT numbers stay below 400 during high power operations, you're getting sufficient fuel flow, no matter what your fuel flow gauge reads.
My suggestion is that you pay attention to your CHTs and do the K-factor calibration flight and adjust the K-factor if necessary.
Happy Flying

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4 months 4 weeks ago #1275

Hi
thanks very much for your opinion. I have a JPI EDM700 with fuel flow option and an OEM fuel flow gauge. They both match so I assume my JPI is set up correctly. My datalogs show about 15.8-16gph during take off and my hottest CHT never really exceeds 370 even in prolonged climbs to FL060-090.

I was just a little bit confused as to why all my cylinders peak EGT just about 50-75F leaner than full rich mixture.
So i see about 1450 on nr2 during take off.. it peaks at just about 1510. Same with other cylinders too. So it looks like sea level full mix full power runs just about 70F richer than peak egt. Everything I read on the internet points to full rich mix should be about 200-250F richer than peak EGT. That is why I thought my fuel flow was maybe not high enough.

But honestly, everything runs great. I just wanted to a 2nd opinion from here and got it!
thanks
Baris

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