(Un)Fit to Print

July 1st, 2011

The majority of folks these days get their news and information from some form of mainstream media outlet.  Which is a shame. Because, while most of us (myself included) assume “they must know what they’re talking about,” when it comes to subjects about which we ourselves have no expertise, it’s on those occasions when they so ignorantly cover a topic of which we DO have intimate knowledge that we then call into question their comprehension of basically anything.

I know stuff about cars.  Alex Taylor III does not.

In a June 27 Fortune Magazine online article (also published on CNN.com), Alex The Third writes about how all the Chevy Volt enthusiasts out there are incredibly misguided because, although the Volt can travel an average of 35 miles on electricity alone, it only gets 32 mpg in the city (36 mpg highway) once the battery is depleted and the gasoline engine turns on.  The upcoming plug-in version of the Toyota Prius, on the other hand, can be expected to get 51 mpg city / 48 mpg highway (same as the current “regular hybrid” Prius) once its battery is depleted after 13 miles of electric driving.  Thus, Mr. 3 contends:  “On trips of 13 miles or less, the Prius plug-in and Volt deliver the same all-electric mpg: zero.  On trips between 13 miles and 35 miles in length, the Volt beats the Prius.  But after 35 miles, the Prius handily outscores the Volt.”

Unfortunately, Alex has failed to understand simple math. The actual cumulative fuel consumption of the plug-in Prius as compared to the Chevy Volt is shown below.  (I’ve used Taylor’s assumptions here, except for the 32/36 mpg that he cites for the Volt.  Although that’s what Popular Mechanics experienced, the EPA figure is 36/37 mpg, and since he uses the EPA figure for the Prius, we might as well be consistent.)

See, the Prius driver doesn’t suddenly overcome the Volt driver with respect to fuel saved at the 35 mile mark.  It takes quite a few miles of the Volt burning gasoline before the break-even point is reached.  In fact, one must drive 97 miles before any fuel-savings is realized by the Prius compared to the Volt.  Which is a lot more than most people drive each day.

But this isn’t even the full story.  I’ve driven both the Volt, and the plug-in Prius (in near-production form).  The architecture of the Volt lets you accelerate hard on electric-power alone.  It lets you reach triple-digit speeds with no help from the gasoline engine.  It has a true all-electric driving range of around 35 miles.  On the other hand, the plug-in Prius is largely the same as the conventional Prius, but with a larger battery.  The low power of its electric motor means that, if you press the accelerator more than just a little, the gasoline engine turns on.  Due to mechanical limitations of the motor-generator attached to the sun-gear of the planetary gearset in its power-split transmission, its electric-only speed is limited to 62 mph.  So if you’re on the freeway (and not stuck in D.C. traffic), the gasoline engine will turn on.  If you try to pass someone, the gasoline engine will turn on.  If you try to drive it at all like a normal person drives a normal car on a normal road, the gasoline engine will turn on.  The 13-mile “electric range” really isn’t.  This pushes the break-even mileage well beyond my generously calculated 97-mile mark.

Don’t get me wrong – the Prius (especially the plug-in version, which is not yet available) is a technically sophisticated, well-engineered vehicle that offers incredible fuel economy, with an internal combustion engine that is more advanced and efficient than that in the Volt.  And it’s true that the charge-sustaining MPG numbers for the Volt are somewhat disappointing (although that’s the penalty for lugging around a large 35-mile battery).  But Alex asserts – in Fortune Magazine – that the Prius is “a better idea” than the Volt, and that the numerous accolades the Volt has received are “an excess of praise in the wrong place.”

Which simply illustrates that he doesn’t know much about either car.

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