[Ken Fry]

Originally Posted by NeilBlanchard

So, MPGe is only really useful to compare different energy sources with a common denominator. The Aptera 300MPGe number would be better if we also knew the conditions of the test.

The "test" was an approximation of 130 mpg at "highway" speed. (50, 55, 60? -- not specified.) This was not a test in the EPA highway cycle -- just some arbitrary constant speed. Here is the text from the part of the Aptera site that explained the calculation: "Sure, it's asymptotic, after 350-400 miles it eventually plummets to around 130 MPG at highway speeds where it will stay all day until you plug it back in and charge it up."

The actual test condition makes little-to-no difference, because using the Aptera rationale of the time, you can make up any figure you want: the idea is to pick one that's very high but plausible. This requires a very long daily drive (to bring the number down to plausible) so the site provided some explanation for how they thought 43,000 miles a year would be a reasonable Aptera usage, (whereas the EPA seems to think 15,000 is typical).

The "300" quoted by Aptera in late 2007 was 300 mpg, not 300 MPGe. There is a huge difference (with the first being just like the 230 mpg Volt first claimed -- just marketing math.) 300 MPGe, on the other hand, represents a very efficient electric car in a standardized EPA test. I think the only reproducible standard test of the Aptera, (at the X Prize) indicated 140 MPGe: better than a Leaf; more like a GM EV1. This test was of a somewhat heavier version than the "300 mpg" one but even it (in plug-in hybrid version) could be advertised as 300 mpg -- because the rationale makes that number have no real meaning.

As if to make the number seem more "real" they sometimes said "up to 300 mpg" as if there was some limit or rational stopping point there. They should have, more accurately, been saying up to infinite MPG. But then maybe people would "get" that mpg measured across charge depleting and charge sustaining modes, is meaningless as a measure of the vehicle.

There are no accurate test conditions required for this kind of marketing calculation, just as there are no test conditions required for me to quote 1000 mpg, 2000mpg 3000mpg, etc. (Which I do for demonstration only.) Truthful... if you are willing to ignore the electric energy consumed.

Edison2 competed in the X-Prize with E85, and they got 110Mpge on the EPA Combined test. They now have built an electric version called the VLCe, and it got 245MPGe on the same EPA Combined test.

I've been intending to look into the actual equivalency figures used by the XPrize for E85. Given the 110 MPGe on ethanol, 245 MPGe seems low. Maybe the AC motor will do better.

Back on topic: Ken do you know an average Wh/mile kind of number for your 39 mile drive? And getting 100MPG in charging mode is an excellent achievement!

The actual drive was 29 miles on electricity, and 1 on gas, which produces an equally meaningless 3000 mpg. (I was extrapolating to the production range. The actual figures don't matter, when using the mpg rationale Aptera did. You can come up with any figure for any car: the Popular Mechanics cover could have been of a 1200 mpg Volt.)

I've been using almost 100 Wh per mile, measured out of the battery. Rolling resistance will be better on the production version, despite weight being higher, because the sticky tires on the POC have high Crr. Aero will be cleaner on the production version. But grades will require more energy in the production version. So I am not expecting any better. I don't think I'll be far below 300 MPGe, but I doubt I will go over that.

Thanks re the 100 mpg while charging. It, too, should be close in the production version, but I am not expecting any higher than that.

Regards, Ken