Get out your calculators

[Save Old Iron 1,571]

I tried to calculate the THEORETICAL running time of a 12 HP Kohler on 1 gallon of gasoline.

 

Paramaters =

 

RPM constant @3600

Gas = 6lbs / gallon

Air = 100 gal per lb.

Air / Fuel Ratio = 15 / 1

12HP displacement = 29 cu inches

 

I get about 40 minutes per gallon (theoretical)

 

????

[tunahead72 2,581]

Okay Chuck, the (lazy) math geek in me wants to know, what's your formula, and where did you get your gas and air weights and the air/fuel ratio?

 

Your final answer sounds about right actually, although I've never tracked my Wheel Horse running times very closely.  I HAVE tracked the running time on my big ole farm tractor (she name Bertha), and it's quite a coincidence that I get almost exactly 40 minutes on a gallon of diesel.

 

Do you happen to know how much a gallon of diesel weighs?

 

[dwayneGT 6]

40 min per gal.= 1/4 gal per 10 min

60 min=1.5 gal

3rd gear,high range@ 3600rpm=7mph

7mph divided by1.5 gal=4.66 mpg (theoretical)

[KATO 115]

In a low compression carbeurated engine at a perfect 14:7 to one ratio,with an engine with a BSFC

of.5lbs per hphr (about normal). It would run 1hr on 1 gallon of gas at pk hp. Assuming this engine is slightly less efficient

and runninng slightly rich at 15:1 I would say your pretty close

[dwayneGT 6]

 Diesel weighs 7.15 pounds per US gallon  ( thanks Bing )

[Anglo Traction 761]

You may want to consider another parameter to the equation, and that is Fuel Temperature. Having played with Civil Aviation Fuel calculations over a longer period than I care to mention, it has an important affect on it's weight, volume and consumption. 

 

 As Dwayne mentions above, the weight of a given fuel, at a given volume, but will only be constant at a fixed temperature. 

 

The colder it gets, the volume reduces, but the weight remains the same.

Equally,  the warmer it is, the fuel expands and the weight still remains constant.

 

So if you have warm fuel, your Carb is passing a metered volume, but less weight of fuel for a given throttle setting.

 

Generic Fuel density tables are usually based on 60 deg F .

 

Sorry if I'm Muddying the Waters even more.   

Edited June 7, 2013 by Anglo Traction