Hi Wayne,

Using Wayne Brown's (WB) simulator, the Prius II is expected to acheive a maximum MPG of about 80 MPG in the 30 - 35 mph range. As you know, the Prius does better than that. I have always thought that the discrepancy lay in the fact the WB obtained his data at steady speeds, in which two additional energy expenditures occur as compared to P&G: 1, More of the ICE->wheels mechanics are creating friction a larger fraction of the time; and 2, the Prius II ICE in the power output range required for steady 35 mph driving of around 4 kW is inefficient.

This last point is a bone of major contention, actually; and as AFAIK, has not been resoved to everybody's content amony the Prius intelligentsia: how good are the Prius brains at lower power output demands. Clearly, the algorithm allows the ICE to produce more power than is demanded by the driver, and shunt the excess to the battery for later consumption, but the efficiency is I think uncertain. And of course the shunting on energy to and from the battery has it's cost.

Bottom line: to the extent that steady rate driving is below the sweet spot of the Prius ICE, P&G will show benefit.

--
Two nitpicks with your analysis to consider:
I have seen estimates of max Prius ICE efficiency of 38%, although there is interplay between rpm and torque, so pinning down exactly where it is has eluded me.

I have to believe you are constitutionaly incapable of NOT drafting , so your accord MPG data may require a fudge factor.

Cheers -- Eric

R2-E2, 2G Prius.
Highway/City/Husband/Wife MPG: 56.5, as of 12/2005, 26K miles

Jac Nasser, Ford President: "We are planning to launch a hybrid version of
this car [P2000] within this year [1998]. We will also make FCEV available in
2004."