2014 BMW i3 (German-market version), Amsterdam, Oct 2013Enlarge Photo
The fuel tank on the range-extended BMW i3 has a capacity of 2.4 U.S. gallons. That would imply a fuel efficiency rating in range-extended mode of no more than 31 mpg (if electric range is 75 miles) to 37 mpg (with a 90-mile electric range).
Limits on speed, power?
Interestingly, a suggestion by CARB staff that the power output of the APU be limited did not make it into the final regulation.
The following language appears in the earlier draft, 2012 Proposed Amendments to the California Zero Emission Vehicle Program Regulations, but not in the final version.
Though not required, manufacturers are expected to incorporate further performance limits on charge sustaining APU mode operation, including speed restrictions. The intent of the backup APU is not to charge the battery, but rather, to enable the vehicle to drive to a charging station. BEVxs will fit the needs of drivers who are looking for an improved regional driving capability, but not for use in long-distance driving.
2014 BMW i3, 2013 Frankfurt Auto ShowEnlarge Photo
In other words, the BMW i3 will apparently not have a speed limiter or imposed limits on the output of its range-extending engine. BMW has not yet released final power or torque figures for the range extender.
Whether or not performance is compromised in range-extending mode--which BMW has said is "not for everyday use"--remains the biggest unknown about BMW's electric car.
At the global media drive last week, a BMW powertrain executive said that i3 users would see virtually no difference in performance between battery and gasoline operation.
Even during a 12-mile uphill grade of 5 percent at highway speeds with four people in the car, he said, passengers wouldn’t notice any difference in performance.
Real-world data sought
The regulations note that CARB will require manufacturers of both BEVx and TZEV cars to provide CARB with data on how they're actually used in the real world.
The board also wants to study how they're used in multi-car households with other vehicles running on gasoline.
That information will let it reassess the regulations (now in effect through 2025) after large numbers of these cars are in use on California roads.
2012 Toyota Prius Plug-In Hybrid, production version road test, San Diego, CA, Jan 2012Enlarge Photo
Plug-In Prius vs Volt
The specific question will likely be whether the presence of an auxiliary engine encourages more driving on gasoline than on the battery.
While that's almost surely the case with many Prius Plug-In Hybrids (which have an electric range of just 11 miles, only 6 of it continuous), it's not the case with the Chevy Volt.
That car has a rated electric range of 38 miles, and roughly two-thirds of all miles in Volts are covered on grid power--not by burning gasoline.
The CARB regulation also notes that in addition to BMW, two other automakers supported the creation of the new BEVx vehicle category: Chrysler and Volkswagen.
[hat tip: Matthew Nelson]