Quote:
Originally Posted by Piwoslaw
Dude, but many of us here try to quantify our mods, though outside of a windtunnel it's only an approximation, as Neil noted. Look and ye shall find. There are a few how-to threads, calculators and spreadsheets on coastdown and rolldown testing. Also, many members have included results in their modding threads (MetroMPG's cardboard boattail is good for a 15% reduction). In some cases it's easier to test the reduction in fuel consumption, which is usually about twice the Cd reduction (very ballpark here).
|
MetroMPG's cardboard boattail was good for a 15% increase in FE (I think this is what you are saying). Metro tends toward doing FE comparissons at a set speed, using cruise control and a Scanguage to measure results. I don't have cruise control, so my FE numbers are kind of sketchy. There are lots of ways to do comparisons, the big thing is documenting what you do and making sure YOUR comparison is apples to apples.
I should have said, my first set of aero-mods was good for about a 7% increase in FE (from a 12.5% reduction in Cd) and my second set was good for about a 6% increase in FE (from another 12.5% reduction in Cd), so the "about 2% Cd = 1% FE" rule is pretty good.