Thread: MPG Tool Math Help View Single Post 09-18-2012, 09:45 AM #3 (permalink) Pb2Au EcoModding Lurker   Join Date: Sep 2012 Location: Texas Posts: 2 Thanks: 0 Thanked 0 Times in 0 Posts Got it now ... I think Watts / Energy Density --> GPH MPH / GPH --> MPG Embarrassingly simple. Watt confused me (pun intentional) are the units of a Watt (N m / s) and a brain cell screaming to multiply by 3600 to get the hourly quantity. This forum is going to be fun. I'll have to blow the dust off my physics book and get back into form. The energy density's time dimension needs to match up to the consumption velocity measurement. hour <--> hour And the energy density's power dimension's time needs to (now obvious for me) match up to the power measurement. second <--> second Work = Force x distance Power = time rate of work So ... some really crazy units can be used with different units of velocity if the reported energy density is consistent with both the power measurement and the rate measurement. Here is a crazy example: Work = lbf * inch POWER = lbf * inch / day ^^ Here the velocity would be inches per day No acceleration, so distance = Velocity if the time frame of interest is same as the measurement unit. Here one day is that unit. ======================================= Energy density = POWER (lbf * inch / day) week / wheel barrow Velocity = inch / week Note how the power quantity is in days and the consumption is in weeks. Inconsistent units!! POWER / Energy density --> wheel barrow / week {volumetric consumption rate} Velocity / (wheel barrow / week) --> inches per wheel barrow {volumetric performance} Perhaps not another soul around that got confused as I did. This posting was for my own sorting things out and for your entertainment.  