Quote:
Originally Posted by AeroMcAeroFace
So we can agree that it is possible to ascertain drag reduction from throttle stop testing?
That is of course assuming the following:
Accessory load is the same (no-air con, no extra lights, heating, etc.)
Tests are done back to back multiple times on the same day to average out any wind changes.
The vehicle is appropriately warmed
The fuel is the same
Whether it is safe to block your throttle, or accurate enough to measure a 1% or 0.5% drag reductions is yet to be decided/ascertained, I will not argue for or against either of those.
|
1) I'm in total agreement that we can.
2) Accessory load will increase at the new, higher velocity, after the aero modification, and we have no baseline data for that.
3) Same for rolling resistance
4) Same for powertrain mechanical efficiency ( it's at a new rpm and lower load )
5) Same for BSFC as the engine is 'blind' to some former signal input
6) From the EPA, we know that A-B-A testing doesn't cancel wind effects, as the vehicle demonstrates different reactions to, say, headwind / tailwind.
7) If we're in 'quartering' winds, there's no available data for that, one way, or another. A complete unknown.
8) Fuel Btu content won't vary.
9) Fuel density ( coefficient of thermal expansion ) WILL vary with temperature, however, probably not, in the timeframes we're working with.
10) As to accuracy, one thing not mentioned, but of some assistance to us, would simply record the fuel economy for a spectra of higher velocities which happen to include the new, higher, velocity-2 with no modifications, to compare to the modified car at velocity-2. Some things could be reverse-engineered from that kind of data.
11) The more 'book-keeping' we can perform, the higher the resolution when attempting to isolate the aerodynamic effects.
12) Qualitatively, the throttle-stop test will demonstrate the trend, without countless hours and liters ( gallons ) of fuel going up in smoke. It's worth the fuss.