Crash diet gets results at GM
Many models are heavier than rivals; new design approach changes that
DETROIT -- When General Motors rolled out the Cadillac ATS compact last fall as the lightest entry in a performance-oriented segment, Mark Reuss noted the irony.
"For the first time, we actually did a car that wasn't bigger and heavier than everyone else," GM's North America president told The New York Times.
Reuss' blunt assessment could serve as a reality check for GM's massive engineering enterprise. While all automakers are working hard to reduce vehicle mass in a quest to meet toughening fuel efficiency standards, GM faces heavier lifting than most.
GM showcased its engineering prowess with the ATS, which, at 3,315 pounds, is 45 pounds lighter than the BMW 3 series; and with the recently introduced Chevrolet Corvette Sting-ray, a trim 3,000 pounds. Yet many of GM's highest-volume vehicles, including the Chevy Cruze and Malibu, are among the heaviest in their segments.
That's forcing GM engineers and executives to play catch-up.
They insist that the weight-conscious approach used to develop the ATS rear-wheel-drive platform -- which also will underpin the redesigned Cadillac CTS due out later this year and the next-generation Chevrolet Camaro due in 2015 -- is now baked into GM's vehicle-development process.
For every vehicle program, mass targets now are approved and monitored by global product chief Mary Barra. Engineers who propose a component or subassembly for a vehicle program must have calculated down to the gram its effect on overall weight. And GM has overhauled a one-size-fits-all approach to developing global platforms that bogged down the Cruze, Malibu and other GM cars with unnecessary weight.
Cutting weight "was an area we should have had a stronger focus on," Barra says. "But we have it now on every vehicle. We are maniacal about mass."
To explain why many of GM's vehicles pack more heft than rivals, Barra points to GM's first crack at developing platforms for vehicles that would be sold around the world, a process begun nearly a decade ago.
The first two architectures under GM's global push were its front-wheel-drive compact platform, which underpins the Cruze, Chevy Volt, Opel Astra and Buick Verano; and a mid-sized platform for the Chevy Malibu, Buick LaCrosse, Opel Insignia and other nameplates.
GM designed both architectures so those vehicles can be sold in markets around the world with little tweaking to meet various safety regulations or powertrain configurations. That saved costs but added pounds.
GM insiders lament that the redesigned Chevy Malibu launched last year is too heavy, hurting its fuel economy and competitiveness in the cutthroat mid-sized sedan market.
"We tended to create architectures that would do everything," says Doug Parks, GM's vice president of global product programs and Barra's top lieutenant. "I'd say we got a little bit inefficient that way."
For example, the engine compartment for the compact platform was designed to handle the largest engine that would go into any vehicle built on it: a 2.0-liter twin-turbo diesel that does service in the Opel Astra. Making room for that beefy powertrain required add-ons, such as reinforcements to the motor compartment rail, even though the vast majority of cars would never need it.
The result: Cruze and Verano owners in North America must put fuel into their tanks a bit more frequently to propel that added weight.
"In the future, if we want to do an uber car like that, we don't want to penalize everyone else on that architecture with the extra mass," Parks says.
Doug Parks: “We tended to create architectures that would do everything. I’d say we got a little bit inefficient that way.”
Priority: Weight loss
Instead, Parks says GM now is committed to developing the lightest platforms possible, and then tailoring vehicles regionally to meet safety requirements or make way for different engine setups. That approach requires extra parts and different tooling in those regions, which adds costs, Parks acknowledges. But "overall you're reducing the mass for everyone."
Jim Hall, principal of research firm 2953 Analytics Inc. in suburban Detroit, doesn't believe GM's new approach to global platform development will result in significantly higher costs. He says it will simply require GM to be more tactical about which markets it enters.
"If a certain market warrants it, they'll optimize the car for that market," he says. "If it doesn't, they won't pay for that differentiation."
When GM engineered its first global platforms, it wasn't strategic about its powertrain strategy, "so they just covered their butts so they could fit almost anything they thought they would need, and that drove mass," Hall says.
At the time, GM was pushing to establish common engineering and manufacturing processes globally, which led the company to "pre-engineer a very wide bandwidth" into each vehicle platform, even if some cars never ended up needing it, Hall says.
"Now, standard processes aren't that big of a deal -- they've got that part down," Hall says. "So they can focus on mass efficiency and ease of differentiation" among vehicles.
Mary Barra: “We are maniacal about mass.”
The Cadillac ATS' rear-wheel-drive platform was the first developed using GM's more nimble approach -- the "proof point" of GM's new religion on mass, Parks says. GM is following that pattern as it develops other platforms, including an underpinning for the next-generation Cruze, expected to debut in 2014.
In the biggest break from past practice, GM engineers built the ATS platform with only the highest-volume model in mind. Initially, they didn't incorporate weightier, more durable parts for, say, a V-6 engine or all-wheel-drive version, says ATS chief engineer Dave Masch.
"We gave the engineers amnesty to be able to push the limit on safety and durability factors to see how well we could perform," Masch says. Later, if parts gave out in lab or vehicle testing, "we would go in and surgically fix that problem, without having to add mass" to the high-volume model.
There were a few things that Masch says "we did in fact break" during testing of the awd model: the front cradle and shocks needed to be reinforced with slightly thicker-gauge material. But the rwd version, which sells in higher volumes, was not saddled with additional weight.
Similarly, GM changed its approach to the development of potential future variants for the ATS, such as a wagon, coupe or convertible. To avoid packing on extra pounds, GM initially did not add components that would make it easier to add a body style later. For example, it's widely expected to offer an ATS coupe as an answer to the BMW 3 series coupe, which will be named the 4 series starting in the 2014 model year. Masch says that not "protecting" for those variants is a break from the past, when GM would tailor a platform's design to easily handle any body style that it might later want to greenlight.
"We'll have to go in and add some reinforcements for those vehicles -- for crash performance or durability or handling -- but without driving mass into the volume ATS," Masch says, declining to discuss the prospect for future body types.
New software helps
Another change since GM developed those first two global platforms: Broader use of a homegrown software system that helps engineers avoid using components that are thicker and heavier than necessary. Created five years ago, the system can run hundreds of thousands of virtual scenarios that test how hundreds of components will hold up at various thicknesses and material types.
"The analysis continually looks at each part -- the gauge, the yield strength -- to zero in on the requirements in terms of vehicle dynamics or safety or durability," says John Calabrese, GM's vice president of global engineering. Engineers can virtually shrink by a millimeter the thickness of, say, a shock tower, and then run an analysis to see how that might affect the performance of dozens or hundreds of other parts.
About three years ago, GM invested $50 million to $75 million in extra computing capacity to run more robust versions of the software. "This stuff will dim the lights," Calabrese says. He believes GM's system is unique in the industry and will give the company an edge in keeping its vehicles as trim as possible.
There are more subtle changes too, including the gram-by-gram approach that engineers now are required to follow. While developing the ATS, engineers tediously included hundreds of "scallops," or little cutouts in the flanges between the welds in the sheet metal. That shaved about 2,800 grams, or more than 6 pounds, from the ATS' body weight.
"Six or seven years ago, we'd have said 'Nah, the view's not worth the climb,'" Calabrese says. "Now it's worth the climb for every gram."
No diet for trucks
Given GM's sharper focus on mass reduction, some industry observers were surprised that the company didn't develop a lighter weight next-generation of full-sized pickups, which was unveiled last month.
The redesigned Chevy Silverado and GMC Sierra weigh roughly the same as the current version, which has been on the market since 2006. Some analysts figured the new pickups would weigh several hundred pounds less than the outgoing trucks.
GM used lighter weight materials throughout the redesigned pickups, including an aluminum hood and engine and high-strength steel for about two-thirds of the cab and much of the frame. But added content offset those savings, GM engineers have said. The new engines should offer better fuel economy, GM has said. The pickups haven't yet been rated by the EPA.
Richard Schultz, managing director of Ducker Worldwide in suburban Detroit, an adviser on mass reduction to GM and other automakers, says GM's current pickups have a 200-pound weight advantage over Ford's F-150. GM's pickups on average weigh 5,037 pounds, compared with 5,236 pounds for the F-150, according to Ducker.
But Schultz believes that Ford could leapfrog GM by shedding as much as 500 pounds on its next-gen truck, due in 2014. Ford is expected to include far more aluminum than GM did on its redesign.
Schultz says GM could be biding its time until later in the decade, when federal fuel efficiency requirements get much tougher, jumping from a fleet average of 35.5 mpg in 2016 to 54.5 mpg by 2025. The EPA target for full-sized pickups jumps to 33 mpg by then, from 17 mpg today.
By then, he believes GM might brandish proprietary weight-cutting weapons that could lead to far greater use of aluminum and carbon fiber by making them cheaper and easier to incorporate into the manufacturing process.
For example, GM says its r&d arm has developed a method to spot weld aluminum pieces together, rather than using rivets to join them, a more cumbersome process that adds weight. GM already uses the technique on the hood of the CTS-V and the liftgates of some SUVs, and plans to expand its use this year.
In late 2011, GM partnered with carbon fiber producer Teijin Ltd. of Japan to dramatically reduce the time it takes to process the strong, lightweight material. If it pans out, GM said the process could be "a game changer" that would reduce the cost of carbon fiber and clear the way for much broader use in high-volume vehicles.
"By 2025," Schultz says, "they'll need to pull out every arrow in the quiver."
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