Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - Tested: what's the resolution of coastdown testing? Can it register an open window?

aerohead · 06-23-2009, 06:34 PM

Darin,I'll be of little help on this one.Sorry! I do believe that it may be asking for trouble attempting to apply "counts" from one development vehicle to another.--------- The least squares method from statistics is supposed to provide a good curve from the coastdown scatterplot,and the slope-intercept at any point along the curve would reveal an accurate time/velocity relationship for the deceleration,from which the forces could be derived.--------- The "scale" of the graph should limit the resolution at the standard deviation.If the RR is well established,the curve would "show" any aero changes if they were larger than the signal-to-noise-ratio.------------- Since an open window "may" show up in a windtunnel measurement for a particular vehicle,it follows, that it would also show up in a coastdown ( no test variables other than body change ) for that particular vehicle.If any environmental factors were to vary during the investigation,the data would be trash.----------- Seems like the Scan-gauge or burrette fuel supply ( as used by students at U.C. Davis ) might be easier for this sort of thing.

06-23-2009, 06:34 PM	#10 (permalink)
aerohead Master EcoModder Join Date: Jan 2008 Location: Sanger,Texas,U.S.A. Posts: 16,404 Thanks: 24,471 Thanked 7,410 Times in 4,800 Posts	resolution Darin,I'll be of little help on this one.Sorry! I do believe that it may be asking for trouble attempting to apply "counts" from one development vehicle to another.--------- The least squares method from statistics is supposed to provide a good curve from the coastdown scatterplot,and the slope-intercept at any point along the curve would reveal an accurate time/velocity relationship for the deceleration,from which the forces could be derived.--------- The "scale" of the graph should limit the resolution at the standard deviation.If the RR is well established,the curve would "show" any aero changes if they were larger than the signal-to-noise-ratio.------------- Since an open window "may" show up in a windtunnel measurement for a particular vehicle,it follows, that it would also show up in a coastdown ( no test variables other than body change ) for that particular vehicle.If any environmental factors were to vary during the investigation,the data would be trash.----------- Seems like the Scan-gauge or burrette fuel supply ( as used by students at U.C. Davis ) might be easier for this sort of thing.