BROWNSTOWN TWP., MI – Andrew Farah, chief engineer on the ’11 Chevrolet Volt, says his team is close to completing validation work on the industry’s first extended-range electric vehicle, but engineers continue to tinker with items such as noise, vibration and harshness.

“It’s like refinishing your bathroom at home,” he tells Ward’s after an event here marking production of the Volt’s first lithium-ion battery pack. “You know where every flaw is. You neighbors would never see them, but you do.

“This car is that home-improvement project. We know where all the flaws are, but I’m almost satisfied,” Farah says.

One sticking point remains NVH issues that arise when the car switeches from full-electric mode to its internal combustion engine.

The Volt is designed to travel 40 miles (64 km) under electric power. After eclipsing that range, a 1.4L gasoline engine kicks on to generate electricity to propel the car another 250 miles (402 km) before a recharge or fill-up is needed.

But engineers continue to wrestle with exactly how much feedback they think passengers should hear and feel when the Volt transitions between those operating modes. Too much NVH would alarm passengers, Farah says. But if the ICE starts too slowly in an effort to optimize NVH, engineers run the risk of depleting the 16-kWh Li-ion battery too far.

A Li-ion battery likes to keep a constant state of charge, never reaching full charge or depleting its charge completely. And a happy Li-ion battery performs better and lasts longer. GM wants its Volt batteries to last 10 years.

“So it’s these finer points we’re working on,” says Farah, who has been using a production-type Volt as his daily driver for several months.

Volt engineers also are in the middle of what is called a “match check” at GM’s Detroit-Hamtramck, MI, assembly plant.

The auto maker invested $336 million to renovate the 24-year-old, 3-million-sq.-ft. (278,709 sq. m) facility last year to accommodate production of the Volt. Now the car’s engineers are making sure all of its body panels match to specifications.

“We want perfect fit and finish,” Farah says.

GM will begin production of the Volt in the fourth quarter, with plans to put customers behind the wheel of the first units by late November. Farah says his team should wrap up validation this summer.

“You can push the software work a little later, tooling for the plant needs to finish up a little earlier, but we don’t want to be making any changes on Halloween night,” he says.

Doug Parks, global vehicle line executive for the Volt, tells Ward’s he expects GM to proliferate Volt’s technology to other GM divisions without great expense.

The recently bankrupt auto maker spent billions developing the Volt, but with its propulsion system complete, additional EREVs probably won’t involve costs any greater than when GM shares platforms between divisions on traditional vehicles.

“The big thing is we don’t want to just re-skin a Chevy Volt,” says Parks, who took over as VLE of the Volt after his predecessor, Frank Weber, jumped ship for a position in his native Europe with parts supplier Magna International Inc.

Instead, GM would engineer the system to fit the brand, which would involve some expense.

For example, if, as widely expected, the propulsion system goes to Cadillac in a vehicle similar to the Converj concept EREV shown at last year’s North American International Auto Show in Detroit, GM might tweak throttle response, tighten the suspension and add bigger wheels and tires.

“We have that capability with the Volt system,” Parks says. “There might be some sacrifices, such as range, but it’s fairly simple” to migrate the system to other vehicles.