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  #1  
Old 05-27-2018, 10:57 AM
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agirard7a agirard7a is offline
 
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Location: Newport, RI
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Default Carburetor jet size

I have an 0320 that I upgraded from 150 hp to 160 hp. I am running lean on climb out and seeing high temps on CHT (over 400) and EGT. (1,300 plus). Fuel flow at 90-95% power is 11gph. Lycoming manual states it should be high 12-13 gph.

I would like to drill out the jet to the next numbered drill size. I have included a photo bellow. What part number actually gets drilled out? Is it the very tip of the nozzle( 1 ) or is it part which is listed as the power jet (4) that appears to look like a gasket. Does the lower part of the nozzle come apart to expose the jet?

For those who have done this, I would love some feed back. Thanks.


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  #2  
Old 05-27-2018, 11:41 AM
YellowJacket RV9 YellowJacket RV9 is online now
 
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Location: Clearwater, FL / KZPH
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It is part #1. One end of it is restricted, and you just drill out that small section. I have done it twice, in two small increments, to get to where I felt happy. First time under the direction of a professional aircraft carb rebuilder, the 2nd time myself. Really not too complicated. Just make sure you buy new replacement gaskets / lock washers for everything that comes apart.

To make sure the hole was drilled perfectly I made a jig to hold the nozzle under a drill press. It is soft metal and drills easily.

Chris
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  #3  
Old 05-27-2018, 01:03 PM
Dreamin9 Dreamin9 is offline
 
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I believe, according to the Lycoming power/FF charts, FF at full power (sea level) should be high 13's for the O-320 160.

Recently I was showing 11.6 gph. Jesse Saint changed the jet size from a 42 to 40. I now burn about 12.7 at full power and it still runs a bit hot, may take it up another notch.

It's my understanding that the diameter of the fuel jet is only relevant at or near full power. At partial power, the mixture control (red knob) is what matters.

Carl
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  #4  
Old 05-27-2018, 01:46 PM
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agirard7a agirard7a is offline
 
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Awesome thanks. Just the info I was hoping for.
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  #5  
Old 05-27-2018, 01:52 PM
jabarr jabarr is offline
 
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Location: Fayetteville, Georgia
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Factory max fuel flow numbers are only for full power/ redline RPM (as stated above). You will not achieve full power/rpm with the fixed pitch prop on takeoff therefore fuel flow numbers will be lower.
You can find a more accurate flow number based on your actual rpm/map if you can decipher the Lycoming charts.

Last edited by jabarr : 05-27-2018 at 02:07 PM.
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  #6  
Old 05-27-2018, 02:03 PM
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snopercod snopercod is offline
 
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An old machinist trick: When drilling brass, round off the corners of the drill bit with a stone. That keeps the bit from "grabbing". That's what I did when I drilled out the nozzle in my MA-3SPA. Mine was the same inner diameter all the way through.
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Old 07-18-2018, 07:46 AM
BABALU BABALU is offline
 
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Location: Nags Head NC.
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Default New carb fuel flow

Quote:
Originally Posted by Dreamin9 View Post
I believe, according to the Lycoming power/FF charts, FF at full power (sea level) should be high 13's for the O-320 160.

Recently I was showing 11.6 gph. Jesse Saint changed the jet size from a 42 to 40. I now burn about 12.7 at full power and it still runs a bit hot, may take it up another notch.

It's my understanding that the diameter of the fuel jet is only relevant at or near full power. At partial power, the mixture control (red knob) is what matters.

Carl
I just had an A&P replace my carburetor on my 0320 160 HP with a new one, my fuel flow is now at 10+ gph when it used to be 8 full rich at the same cruise RPM. I have one CHT that is running about 50 degrees cooler now than the others when before all was pretty consistent. I relayed this info to the A&P and he said its because its a new carb and that it will just have a higher fuel flow and to just lean it out. Im no mechanic but i think the jetting needs to be adjusted.
When leaned at altitude and cruise RPM i was at 6.5 before i havent messed with the mixture yet because im not comfortable with what im seeing yet so i dont know where im at with that now. Ive flown this RV over 500 hrs before the new carb was installed and i know where it should be , im not liking the new numbers. Any input? Does it need to come off?
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  #8  
Old 07-18-2018, 10:56 AM
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agirard7a agirard7a is offline
 
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Quote:
Originally Posted by BABALU View Post
I just had an A&P replace my carburetor on my 0320 160 HP with a new one, my fuel flow is now at 10+ gph when it used to be 8 full rich at the same cruise RPM. I have one CHT that is running about 50 degrees cooler now than the others when before all was pretty consistent. I relayed this info to the A&P and he said its because its a new carb and that it will just have a higher fuel flow and to just lean it out. Im no mechanic but i think the jetting needs to be adjusted.
When leaned at altitude and cruise RPM i was at 6.5 before i havent messed with the mixture yet because im not comfortable with what im seeing yet so i dont know where im at with that now. Ive flown this RV over 500 hrs before the new carb was installed and i know where it should be , im not liking the new numbers. Any input? Does it need to come off?
What flow are you seeing on climb out? 160 hp should be mid 13 gph according to Lycoming manual. You can always lean in cruise. High CHTís on climb was my issue that I am still working on. Iíve decided to open up the snorkel entry for air intake. More air intake will Venturi more fuel flow.
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  #9  
Old 07-18-2018, 11:43 AM
BABALU BABALU is offline
 
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Location: Nags Head NC.
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Hi Al, im seeing 13.5 on climb out i get two cylinders in the low 400 range on climb out then all is good after that , i just try not to climb to aggressively in the summer especially. Im fine with all my CHTs as per lycoming. The new high fuel flow at cruise is not acceptable though for me and im concerned about that .
BTW i was in Newport the first week of june with my RV9A. Black white silver.
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  #10  
Old 07-18-2018, 02:32 PM
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agirard7a agirard7a is offline
 
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Default Leaning

Have you been leaning at cruise? You should be able
To lean it back to 6.5-7. If your getting 13s on climb out, it leads me to believe
Your good on your jet size.

You can put in a smaller jet if need be. There is a part number scribed on the jet. Call Marvel Shibler and see if it is the right size for your carb or order a smaller one.
Easy to install. Or have your AP put it in.
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