Road Horse Power x 0.7457 = Road Kilowatts
 

In my original thread on Road Horse Power I posted I had reached 18.2 mpg at 80 mph. That is a 17.1 % improvement over the truck naked. My goal is to see if I can reach 20 mpg at 80 mph which would be nearly a 25% improvement in highway mileage. I have already recorded a 22.7 mpg at 70 mph with a 4 mph head wind on a 68 degree day so I think this will be very doable. We recorded a 23.7 mpg at 75 mph with a 4 mph tail wind during this test also. This is effectively 23.7 mpg at 71 mph and 22.7 at 74 mph.

Truck Naked 48 F 80 mph = 15.1 mpg = 64.2 RHP = 47.87 RKW's
Aero/Boat Tail 48 F 80 mph = 18.2 mpg = 53.3 RHP = 39.74 RKW's
Goal with Aero 80 F 80 mph = 20.0 mpg = 48.5 RHP = 36.17 RKW's

(Note 80 F should give me an effective air density of 6,300 ft of
elevation here in southern New Mexico at 4,000 ft) I would need
retesting to establish true baselines.

Mileage would be much higher at lower speeds of course but I consider the 80 mph test to be very critical in evaluating performance. I can perform the test on local interstate highways where the limit is 75 mph. While technically speeding I can do the test in 2 or 3 minutes on open level ground and with good visibility I can hopefully avoid a ticket.

I am throwing out my 40 mph data because the truck is often in 5th gear at this speed. I need to restrict myself to 6th gear data. For example the other day at 40 mph in 5th gear at 1300 RPM we registered a 31.5 mpg. At 45 mph in 6th gear at 1050 RPM we registered a 31.5 mpg also. This amounts to a energy consumption rate of 11.47 RKW's v 12.9 RKW's respectively which are the actually the same normalized over distance.

While the efficiency may look the same it is not. In 6th gear I can use the same amount of energy to go 5 more miles then I can in 5th gear at the same burn rate. To make a apples to apples comparison all data needs to be in the same gear.

You're not gonna get a ticket for going 5mph over the speed limit, and that's not even acting carelessly. For science! I'm interested in how this turns out, 20mpg at 80mph in a truck would be amazing.

We just need warmer weather. If we can get some belly pans installed I think this would make the difference. I am looking at 36 sq ft of belly pan work that ought to be fairly easy to do. I got my barometer reset for sea level again so it is now uncorrected. I will be able to use it for data gathering again.

We pulled a 19.6 mpg at 80 mph with the Aerolid only. It was 67 F and the baro was at 26.13. We had a 2 mph wind out of the SW and we were headed north. It is looking more and more like 20 mpg is easily doable with a boat tail added.