Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - The BSFC chart thread (post 'em if you got 'em)

johnQ · 06-20-2009, 06:21 AM

Hi, I am new here, I registered just for this interesting topic. I am a former physycist.
In principle it is possible to measure BSFC in not professional conditions.
You must have access to reliable fuel consumption measurment. Some newer cars display this quantity. If you have this together with rpm display, you can measure BSFC on standard dyna chassis. Just make several dyna tests with different throttle opening and film with camera (even callular phone camera) what is fuel consumption and rpm. Than you can combine dyna plots with filmed data and make bsfc chart. It will be even better then presented ones because it will show overall efficiency together with gearbox losses.
In principle it is also possible to measure it without dyna chassis. You must have a nice flat road and no wind at all (like sometimes in the evening). Then there should be a fixed relation between speed and power losses. If you know the mass of your car (together with a driver and fuel) then you can film how your car is losing speed at free gear. Of course couple of measurments are better then one. Then you can find this dependency. Then film how the car is accelerating at some throttle opening together with fuel consumption. (of course you can combine both measurements i.e. accelerate and then loose speed at no gear) That is just a method how to replace dyna chassis by a mass of the car. Such measurement is perhaps closest to what one wants to do in real-world economical driving. The point is in controlled conditions. If the road have some slight slope you must measure it driving in both directions but it must be flat. And if there is some wind it will ruin everything. The best is to measure everything couple times and combine results on one chart with errorbars. In fact analog (clock type) controls may have some inertia and lcd display of fuel consumption may be not very accurate. The best would be if one could directly connect to the computer of the car and record values on a laptop (on dyna chassis as well). Just the idea. When I buy a better car I will try to measure it.

06-20-2009, 06:21 AM	#141 (permalink)
johnQ EcoModding Lurker Join Date: Jun 2009 Location: poland Posts: 3 Thanks: 0 Thanked 0 Times in 0 Posts	measuring bsfc Hi, I am new here, I registered just for this interesting topic. I am a former physycist. In principle it is possible to measure BSFC in not professional conditions. You must have access to reliable fuel consumption measurment. Some newer cars display this quantity. If you have this together with rpm display, you can measure BSFC on standard dyna chassis. Just make several dyna tests with different throttle opening and film with camera (even callular phone camera) what is fuel consumption and rpm. Than you can combine dyna plots with filmed data and make bsfc chart. It will be even better then presented ones because it will show overall efficiency together with gearbox losses. In principle it is also possible to measure it without dyna chassis. You must have a nice flat road and no wind at all (like sometimes in the evening). Then there should be a fixed relation between speed and power losses. If you know the mass of your car (together with a driver and fuel) then you can film how your car is losing speed at free gear. Of course couple of measurments are better then one. Then you can find this dependency. Then film how the car is accelerating at some throttle opening together with fuel consumption. (of course you can combine both measurements i.e. accelerate and then loose speed at no gear) That is just a method how to replace dyna chassis by a mass of the car. Such measurement is perhaps closest to what one wants to do in real-world economical driving. The point is in controlled conditions. If the road have some slight slope you must measure it driving in both directions but it must be flat. And if there is some wind it will ruin everything. The best is to measure everything couple times and combine results on one chart with errorbars. In fact analog (clock type) controls may have some inertia and lcd display of fuel consumption may be not very accurate. The best would be if one could directly connect to the computer of the car and record values on a laptop (on dyna chassis as well). Just the idea. When I buy a better car I will try to measure it.