Engineering the 2016 Chevy Volt


The unsurprising thing about Pamela Fletcher, executive chief engineer, Electrified Vehicles, General Motors, is that she is a graduate of the then-GMI (now Kettering University). Plenty of engineers at GM (and elsewhere) attended GMI (or Kettering).

What is somewhat more unexpected is that Fletcher, who heads up the engineering for the GM portfolio of cars that are run by electric motors—the Volt, the Cadillac ELR, the Spark EV, and the forthcoming 2016 Cadillac CT6 plug-in hybrid and Chevrolet Bolt EV—is that she has a master’s degree . . . in combustion.

Which is not to say that in some cases—as in the Volt—there aren’t internal combustion engines involved, but in the case of that vehicle, Fletcher explains, the point is to use the engine as to serve primarily as a generator. But it is part of the “Voltec” electric propulsion system. For the 2016 Volt, there is a new engine—referred to as a “range extender.” It’s an all-aluminum 1.5-liter four that produces 101 hp at 5,600 rpm. In the first-generation car, it is an 84-hp 1.4-liter engine that produces 84 hp @ 4,800 rpm. And even though the current engine is bigger and provides more horsepower, it (1) runs on regular unleaded, not premium and (2) provides 41 mpg compared to its predecessor’s 41 mpg.

But Fletcher really talks with a whole lot of pride about the improvement on the battery/motor system, although she emphasizes the system aspect of the vehicle.

And what they’ve been able to accomplish is a system that provides an EPA-certified 53 miles of purse electric range, which is almost 40% better than the gen-one vehicle (38 EV miles).

What is all the more impressive about what they’ve achieve is that the lithium-ion battery has 96 fewer cells than the previous generation (it uses 192), yet it has more power (18.4-kWh).

The new and improved—and this is a case where those terms do apply, as if you were to look at the battery case, you might think, “Hey, that looks just like the other one,” with all of the improvement being inside—lithium-ion battery is 21 lb. lighter than its predecessor. And the number of components have been reduced by 
a third.

Fletcher points out that the team worked diligently to reduce the overall weight of the car by over 200 lb. (3,543 from 3,781 lb.): “We were chasing tenths.” About 100 lb. were taken out of the propulsion system.

One of the interesting comments that this engineer makes is that when they developed the first-generation Volt, a car for which there was no existing template within or even without the GM portfolio, there was no template. “There was a lot of engineering judgment the first time around.” But for the second-generation, Fletcher says, they listened to what the customers said, and they had OnStar-sourced data on what the actual customers were doing with their Volts. This, she explains, supplemented the first-rate engineering they performed.

What did the Volt customers look for? “When we asked the customers, the number-one response was greater electric range,” Fletcher answers. And adds that that was pretty much the answer for the top-10 list of customer desired.

The 40% improvement. They clearly listened.—GSV