BMW i3 REx Electric Car: 'Coding' Unlocks Features Owners Want (And May Void Warranty)

The BMW i3 REx model is an unusual beast, the sole example to date of a car built specifically to comply with California regulations that define it as a zero-emission electric car even though it has a range-extending engine.

That's because its gasoline range (EPA-rated at 78 miles) is more or less equivalent to its battery range (EPA-rated at 72 miles).

How does BMW manage that? By restricting drivers' ability to fill its tiny gas tank to a minimal 1.9 gallons (7.2 liters).

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That restriction in turn frustrates eager i3 REx drivers who want to use their cars on trips without having to stop every hour or so to add $5 or less of gasoline on long road trips.

While some i3 REx drivers swear they can do a quick fillup in less than two minutes, meaning it has minimal impact on travel time, the European version of the i3 REx has a larger tank capacity: 9.0 liters, or 2.4 gallons--enough for about 20 extra miles.

The European i3 REx also has a mode that allows users to conserve battery energy if they know high levels of power will be required in near-term future driving: on hills, for example.

So what's a BMW i3 REx owner to do?

At least some are choosing to follow instructions posted online and in BMW forums to "code" their cars--which is to say, modify the car's software to provide these functions.

That, not surprisingly, is highly frowned upon by BMW, for a very rational reason. Software updates could go awry, creating safety hazards from modified electronic control systems that operate every aspect of the car.

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Nonetheless, at least a few intrepid i3 REx owners have enthusiastically taken to coding their cars.

A partial list of functions that can be added or modified with those updates includes:

• Allowing fuel tank to accept full capacity of 2.4 gallons

• Adding suppressed European "hold battery charge" function

• Enabling suppressed AM radio

• Suppressing U.S.-mandated seat-belt warning tone

• Permitting video to be run from USB storage device

• Changing startup image (one owner found "a cool Alpina" emblem hidden in the car's software)