Save Old Iron 1,563 #1 Posted June 7, 2013 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) ???? 1 Share this post Link to post Share on other sites
tunahead72 2,332 #2 Posted June 7, 2013 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? Share this post Link to post Share on other sites
dwayneGT 6 #3 Posted June 7, 2013 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) Share this post Link to post Share on other sites
KATO 115 #4 Posted June 7, 2013 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 Share this post Link to post Share on other sites
dwayneGT 6 #5 Posted June 7, 2013 Diesel weighs 7.15 pounds per US gallon ( thanks Bing ) Share this post Link to post Share on other sites
Anglo Traction 759 #6 Posted June 7, 2013 (edited) 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 Share this post Link to post Share on other sites