Interesting because I actually realized increased mileage with the TG down. I have not modeled the air currents with "smoke" but I did fill the gas tank and check the mileage. I got between 3 and 5 miles per gallon better with the tail down at different times. I'm one of those people that saves receipts and write the mileage down on it so when I fill the tank again I can calculate the mileage. But I don't do all highway driving. I get about 20 mpg plus or minus on my V6 in 2W HD. I never checked it in 4W HD or 4W LD. I only use 4W LD to pull the backhoe or trailer. I wonder if I were to put NTC thermistors in strategic places and pulse them to avoid self heating error, could I collect the air flow measurements with the TG up and TG down? Also if I correlate the airflow at those points with the velocity of the vehicle could I actually model the fluid kinematics? And, if the drag is increased with the TG down to the extent that it increases fuel consumption it would seem that additional energy would be required from the engine; similar to turning on the head lamps or air conditioning. Could the tach to speed ratio be recorded in continuous real time with the TG up versus TG down? Of course, the delta drag may be too insufficient to cause a measurable delta RPM. It could be fun to do some of this. Just a kind of fun project with no pressure to meet a dead line. ----- Original Message ----- From: "Jinx" To: "Microcontroller discussion list - Public." Sent: Wednesday, June 27, 2007 7:03 PM Subject: Re: [EE] Simple fuel-saver, so they say > > >> I drive with the tailgate down when I use the pickup unloaded. It >> does save fuel because up, it can scoop up enough air pressure at >> 50 mph to cause significant drag > > Mythbusters claimed that with the tailgate down, the vortex behind > the cab disappears. According to the pick-up manufacturer (smoke > trail test film), air coming over the cab roof bounces off that vortex, > resulting in less drag > > http://www.cartalk.com/content/columns/Archive/1997/October/05.html > > As they say there, it's counter-intuitive > > Not that I'm doubting your results, you know your vehicle and > have the numbers > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist