Formula for Fuel Consumed by PTO

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Anonymous Poster #1	Formula for Fuel Consumed by PTO 03/26/2013 2:52 PM
	Does anyone have the right formula or rationale for additional fuel consumed to operate PTO equipment. I have two for diesel applications from different sources and one appears to be wrong. They are: A X B X 0.543 = liters per hour or [(A X B X 0.543) + 2] / 2 = liters per hour Where A is the fuel consumption in lbs/bhp from the engine performance curve chart for a specified RPM and B is the horsepower of the PTO in normal operation. As you can see, the first answer would be nearly twice the second.
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phoenix911 Guru Join Date: Aug 2007 Posts: 23647 Good Answers: 420	#1 Re: Formula for Fuel consumed by PTO 03/26/2013 3:00 PM
	PTO?????? ah... Power Take-Off? __________________ “ When people get what they want, they are often surprised when they get what they deserve " - James Wood
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Doorman Guru Join Date: Apr 2009 Location: Yellowstone Valley, in Big Sky Country Posts: 7425 Good Answers: 295	#2 Re: Formula for Fuel consumed by PTO 03/26/2013 3:05 PM
	"Where A is the fuel consumption in lbs/bhp..." I am prepared to wager this isn't correct. __________________ Semper Ubi Sub Ubi
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Barry Hutchinson Participant Join Date: Mar 2013 Posts: 2	#7 In reply to #2 Re: Formula for Fuel consumed by PTO 03/27/2013 9:10 AM
	"'Where A is the fuel consumption in lbs/bhp'... I am prepared to wager this isn't correct." Thanks Doorman. Bigg is correct. I meant to say lbs/bhp - hour. Your tag takes me back to Gr 10 Latin (a long way back) Jockey or briefs? illegitimati non carborundum (forgive the spelling?)
	Reply Off Topic (Score 5)

lyn Guru Join Date: Oct 2008 Posts: 42355 Good Answers: 1693	#3 Re: Formula for Fuel consumed by PTO 03/26/2013 3:05 PM
	The manufacturer SHOULD have that information. Otherwise, SWAG it.
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bigg Guru Join Date: Jun 2010 Posts: 1296 Good Answers: 104	#4 Re: Formula for Fuel Consumed by PTO 03/26/2013 3:27 PM
	1. the units of A should be lb/bhp-hr (specific fuel consumption - SFC) 2. the units of 0.543 would be liters/lb (giving a density of 1.84 lb/liter). Converting to units I am more familiar with, this is equivalent to 6.98 lb/gal, which is about right for diesel fuel. So there's your rationale for the first equation. As long as you take SFC off the performance chart and don't treat it as a constant, you're good to go. The second equation may be someone's attempt to use a constant for SFC and then add a constant (2) to account for additional fuel usage due to inefficiencies at low loads, but I don't know, and the 'divide by 2' sure doesn't look right.
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Tornado Guru Join Date: May 2009 Location: Richland, WA, USA Posts: 21017 Good Answers: 795	#5 In reply to #4 Re: Formula for Fuel Consumed by PTO 03/26/2013 3:56 PM
	Agreed. You've said sooner and better what I was about to say. __________________ In vino veritas; in cervisia carmen; in aqua E. coli.
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Barry Hutchinson Participant Join Date: Mar 2013 Posts: 2	#8 In reply to #4 Re: Formula for Fuel Consumed by PTO 03/27/2013 9:41 AM
	Thanks Bigg. My gut feeling about equation 2 was similar to your comments. I could understand part of an equation being omitted by mistake if it happened (equation1), but no one would add factors without some rationale for it, wrong though it may be. Isolating the consumption for a specific power take off from other power draws (parasitic, idling) seemed the most likely. But since the equation 1 result is already a factor of the hp requirement of the PTO alone, a further reduction would appear redundant. I'll phone the manufacturer.
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dhayanandhan Guru Join Date: May 2008 Location: CHENNAI, TAMIL NADU, INDIA. Posts: 1851 Good Answers: 65	#6 Re: Formula for Fuel Consumed by PTO 03/27/2013 4:19 AM
	Dear Friend, Your Question is not clear. Pl. elaborate. There is a say, understanding the question is equal to Half-solved. DHAYANANDHAN.S
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