General Motors Co. executives say sales of the new-for-’11 Chevrolet Cruze and Buick Regal are gaining momentum after capacity constrained launches for the two compact cars.

“We doubled (Cruze) sales last month,” GM North America President Mark Reuss tells Ward’s on the sidelines of the North American International Auto Show.

After launching initial builds of the Cruze in September at GM’s Lordstown, OH, assembly plant, the car’s production reached full line speed last month.

Jim Graham, president of United Auto Workers union Local 1112 at Lordstown, told Ward’s earlier the slow ramp-up was put in place to ensure a squeaky-clean launch.

GM earlier wanted to pull ahead the launch to further distance the Cruze from redesigned competitors arriving later this year but reversed those plans.

The auto maker’s deliberate launch also left dealers short on Cruzes, a dilemma Reuss says the auto maker remedied in December. GM insiders also have confided to Ward’s their disappointment over the Cruze’s early sales results.

“There’s a bit of a lag between when you hit line rate and what you can get in the field and what you sell.

“Every time we launch a car, we want it as close to perfect as it can be,” Reuss says. “So we made sure that happened. We’ve got a lot at stake on that car.”

GM sold 10,865 units of the Cruze in December, up 19.7% from November.

So far, the auto maker has delivered 24,495 Cruzes, a vehicle expected to approach the 200,000-unit mark its predecessor the Cobalt delivered annually in its best years.

Reuss says additional powertrain availability also has helped sales. GM launched the Cruze with a 1.4L turbocharged 4-cyl. engine, which it expects to comprise the volume of sales, but also recently added a more economical 1.8L to the mix.

Reuss expects a Cruze Eco model arriving at dealers this month and achieving 40 mpg (5.9 L/100 km) to further boost sales. A 6-speed manual for the 1.4L also arrives later this year.

Deliveries of GM’s highly anticipated Regal sports sedan also started tepidly, blamed on the limited availability of its 220-hp, 2.0L turbocharged 4-cyl. engine.

The car launched with a 182-hp, 2.4L direct injection 4-cyl. engine, a Ward’s 10 Best Engines winner in other applications but arguably short on punch for its segment.

Last month, the auto maker sold 3,059 units, up 37.4% from prior-month with the turbo in the mix. Since its arrival in May, the Regal has accounted for 12,326 sales.

In addition to the single engine choice early in its launch, the Regal also has been selling with just one trim level. Until production begins next year at GM’s Oshawa, ON, Canada, assembly plant, the car is being imported from Russelsheim, Germany, where the auto maker builds its European twin, the Opel Insignia.

“The turbos are just arriving here in December and…we’ll be able to grow availability,” says John Schwegman, marketing chief for Buick-GMC. “We’ll have the second half of the portfolio. We’re starting to get some traction.”

GM also launches the new-for-’11 Buick Verano compact luxury car later this year with the 2.4L and will wait roughly one year to add the 2.0L turbo to its portfolio. But the Verano is a different car, Schwegman notes.

“(The) Regal is more of a performance-oriented sedan; (the) Verano in a lot of ways is like a baby LaCrosse,” he says, referring to the bigger, more luxurious premium sedan launched last year.

“We tuned it accordingly, so we think the mainstream 2.4L engine is going to be the bulk of the volume (for the Verano),” Schwegman says.

He also says GM has not publicly set a more specific date for the Regal’s production launch at Oshawa beyond “tail-end of quarter one.”

jamend@wardsauto.com