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Old 18-04-2008, 07:17 PM   #1
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Gph

Having a clear-out, found this file, dunno where from (most likely here).
Q1. How does it work out with you-all?

1/2 of your horsepower divided by 6.23= GPH. This is just a rule of thumb.

Q2. Where does the "6.23" come from?
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Old 18-04-2008, 07:36 PM   #2
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Q2: that was the 'fudge' required to make the numbers work. It would be a different 'fudge number' to make it work in litres per hour...


V24 = 1.6 litres per mile at fullspeed.
75 miles in 1 hour.
1.6 litres x 75miles = 120 litres = 26 gallons

320 Hp = 160/6.23 = 25.7 So it works for the V24.......
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Old 18-04-2008, 07:41 PM   #3
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OK fine, where did the 'fudge' derive from?
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Old 18-04-2008, 07:52 PM   #4
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Extrapolation to make the 'world' numbers - in this case GPH relevant to the other 'world number' ie horsepower.

If you think there is a constant relationship between anything and something else, you can extrapolate to determine a 'constant' number. If something is always reproducable with trial after trial you can calculate the constant.

For a bad example: The number of beers drunk in a certain amount of time would give a rating of the uglyness of the bird you would pull. Unfortunately there are too many variables for this to be accurate, but as a very rough rule of thumb, the more you drink the more likely you are to pull the ugly bird. You can take a series of observations and calculate a formula, and apply a constant till the observations match the formula. If it was nicely repeatable, you could always determine the uglyness of the girl by the number of pints drunk.

This is not repeatable, mostly because women are involved, but hopefully you get the theory.

So you have an idea, you apply the theory to the idea ( in this case the HP produced by an engine is related to the fuel burned ) then you apply a constant so that the figures in the real world match each other.
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Old 18-04-2008, 07:56 PM   #5
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Anybody else!
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Old 18-04-2008, 07:57 PM   #6
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Isn't it just the 1 US gallon for every 10HP estimation convereted to UK gallons.
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Old 18-04-2008, 07:59 PM   #7
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Maybe, but where did that evolve & how ????
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Old 18-04-2008, 08:13 PM   #8
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Quote:
Originally Posted by Wayne Kerr View Post
Maybe, but where did that evolve & how ????
Just a rough estimation , no science I suspect.
If you took a handfull of different model 10 HP engines and fed them with a gallon of fuel they would average out about an hour at WOT before they ran dry. But some would be better than others
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Old 18-04-2008, 08:56 PM   #9
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Roger that 162, the equation denotes that I do 12.6 (ish) gph. Actual results record that 5.4 is a more realistic figure for me!
OK, not at WOT all the time, but most of.

Just wondered where the figures came from?
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Old 18-04-2008, 09:16 PM   #10
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If you are not WOT you are not producing the rated Hp, so it should not work for pottering around the thames on a sunday afternoon.....

Conversely you can thumbsuck calculate the Hp of your engines at say 3500rpm by calculating the fuel usage at that RPM.

I am stunned that the maths worked for the V24 engine. For the Bladerunner it looks a little diffrerent..

Bladerunner = 60 gallons per hour WOT

600 Hp = 300/6.23 = 48 gallons for the calculation - But I know the fuel usage exactly - So it does not work for a set of 300 promax engines... Which may be because they are two stroke and the calculations were derived from four stroke engines.....

320 Hp = 160/6.23 = 25.7 So it works for the V24.......
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