Testing the Range Extender - 2014 BMW i3 Long-Term Road Test

2014 BMW i3 Long-Term Road Test

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2014 BMW i3: Testing the Range Extender

March 3, 2015

2014 BMW i3

I knew I'd be driving 40 or so miles to Simi Valley, Calif., and back to visit the in-laws. I also knew I'd be making a return trip to downtown Los Angeles. There was any number of regular old gasoline-powered cars available with hundreds of miles of range, and yet, I chose to take our long-term 2014 BMW i3. It was time to test its range-extender engine.

Stuffed under the i3's trunk floor is a 647cc two-cylinder gasoline engine that serves as an emergency back-up should you need to go beyond the i3's electric range. It's a safety net, not the makings of a true plug-in hybrid, as its rinky-dink 2.4-gallon tank means you'd be hard pressed to drive very far.

We reached Simi Valley with 8 miles to spare on the battery, but the round trip to dinner with four aboard killed that remaining range. This was the first time I had experienced the range extender, which sounds a bit like someone is running a sewing machine in the trunk. It's frankly hard to notice when moving, but once the car is stopped, it is louder than the typical engine and produces more vibration (generating electricity and therefore not being at idle is a big part of that). However, it should be noted that, like a hybrid, it can shut down when the car stops if there's enough juice in the batteries to keep everything functioning.  

In this suburban driving around Simi Valley and during the next day's journey into downtown Los Angeles, running on the range extender was perfectly pleasant. That initial burst of perfectly smooth and eerily quiet all-electric propulsion is still available, and despite adding engine noise to the equation, I wouldn't classify it as objectionable.

Having said that, I did experience the range extender's limitations. Despite using the i3's Eco Pro mode and accelerating economically leading up to the grade out of Simi Valley, the little engine had trouble keeping up with the increased electricity demands. No matter what I did with the accelerator, my speed gradually dropped from 74 mph down to 56 mph by the time I reached the summit. It would've kept going down had the grade been any higher or steeper. It was reminiscent of driving the Chevy Volt to Death Valley when I was reduced to a 28-mph crawl despite my foot being planted to the floor and the engine crying bloody murder. The i3 didn't get that bad, but we were certainly hearing its discontent.

2014 BMW i3

That climb also didn't do much for the gasoline engine's range. As we later approached the Sepulveda Pass on southbound Interstate 405, the DTE meter read 26 miles. The navigation system said we were 21 miles to home. With another grade looming and my wife worrying, I stopped for a splash of fuel. Although, in the i3, a 1.1-gallon splash of fuel is good for half a tank.

Now, as it turns out, we actually would've made it home with 11 miles of range left since the Sepulveda Pass is clearly steeper and longer on its south side where the i3 mostly coasted and recharged its battery. Yet, this episode clearly demonstrates that opting for the range extender does not eliminate range anxiety. Rather, it simply transfers it from the battery to the tiny gas tank.

In case you're wondering, I got 32.6 mpg with the range extender. The initial highway bit with the grade out of Simi Valley was 26.6 mpg (the first fill) and the remainder, mostly around town and in traffic, was 38.3 mpg (the second fill). Keep in mind that this amounts to a very small sample size with an extremely small amount of gasoline burned.

In the end, my time with the range extender proved that you should avoid large highway grades and that an extra gallon or two in the gas tank would be helpful. However, it is still worth that extra amount of payment as I couldn't have accomplished the journey at all without it.

James Riswick, Automotive Editor @ 2,701 miles


2014 BMW i3

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