Hi,
I've been reading this paper closely and I think I found why their results, 25% improvement, versus mine, 11% are so different. If I read the paper correctly, they did their vehicle tests using a dynamometer and their model does not include aerodynamic drag effects. I've sent an e-mail invitation to discuss their paper in a public forum. Also, I suspect they did not include what Ken@Japan has called the 'heartbeat' or the ~300-400 W of power needed when the Prius is just sitting there. This power runs the electronics and electric assisted brakes and steering.
To show you what I mean about the 'heartbeat' load:
The 'blue' line is the expected MPG for my NHW11 based upon a drag formula published by Toyota. But when I add the fixed, vehicle overhead, I get the lower, 'gray' curve that shows there is a peak range speed in the 18 mph range. Any slower and the fixed overhead begins to predominate. Any faster and the aerodynamic drag effects reduce mileage.
I think this paper, "Vehicle Inertia Impact on Fuel Consumption of Conventional and Hybrid Electric Vehicles Using Acceleration and Coast Driving Strategy" Jeongwoo Lee, Douglas J. Nelson and Hennning Lohse-Busch used just 'road' constants (pp
2 and
3) and not aerodynamic effects. This makes sense when comparing the 2007 Ford Focus and 2004 Prius on a dynamometer (pp.
4). So when I look at "Table 4. Summary of Results of 2004 Toyota Prius" (pp.
6), I'm wondering why these data points are off by a factor of 2 from
my field results.
Bob Wilson