Thursday, Aug 25, 2011 at 14:29
Fuel flow meters are just that, they measure first and foremost the actual fuel supplied to the engine, and therefore provide a very accurate reading on fuel burn. All other calculations it makes are derived from this. “Long term measurement does not rely on multiple readings that compound into errors”.
But I did qualify, in my first response, that the use of a fuel flow meter in a vehicle to get a snapshot at any given point of time on ‘fuel flow rate’ will be difficult because power settings in a vehicle are not constant. And you are correct to say that simply relying on a ‘fuel flow rate’ reading at any point of time is not helpful for forecasting range.
However, it still measures quite accurately actual fuel supplied to the engine (actual fuel used) and therefore at any point of time you (or the device) can calculate actual fuel used for the distance travelled; the average burn rate. It does not rely on multiple readings to calculate actual fuel used. So no need to wait until the end of the day to calculate the fuel you have used, it is available to you at any point of time. Besides, the calculation you make at the end of the day is still an ‘average burn rate’ whether you measure into the tank by volume or weight.
I flew many aircraft with fuel flow meters, and most were usually linked to NMEA output, so a range and fuel usage to destination could automatically be calculated. Because aircraft are generally flown at a constant power setting you can simply glance at the fuel flow per hour to gain an insight to ‘fuel burn’. But another way of doing it was to simply take the actual fuel used to any point of time, and compare it against the distance travelled to calculate the ‘average’ burn rate per kilometre. You could do the same in a vehicle at any point of time quite accurately.
I’m sure there will be many EO members who have used similar in either larger motor boats, or possibly aircraft. But again, I don’t suggest we all spend $1,000 on having our vehicles fitted with them as for most it would be an over kill. But for regular, long-range remote desert travellers it may well be a great investment and viewed as a safety aid...
The discussion on fuel flow meters is an aside to your original proposition. And as I qualified earlier, whatever works well for you is best for you. However, I can’t accept that by determining fuel usage via a weight calculation improves the process of determining fuel usage any more so than by measuring by the volume you are adding, which I think is the point you are endeavouring to make.