Phi Beta Kappa
GM’s cost-effective strategy for shifting Pontiac into gear.
How do you reinvigorate a car division? In the case of Pontiac — with 2003 calendar sales slipping 8-percent from 2002 volume — drastic action is the only viable plan. That means roasting lame ducks such as the Aztek and restocking shelves with more vibrant models like the GTO and Bonneville GXP.
But if you’re serious about resuscitation, you go for the double whammy — low price and sex appeal on one set of wheels. Lightning struck 40 years ago with the original Mustang and Chrysler’s sub-$20,000 PT Cruiser was a coup in 1999. A shot of $20,000 two-seat roadster would surely cure Pontiac’s doldrums.
Credit GM’s car czar Bob Lutz for conjuring up the Pontiac Solstice as his first act after walking into the executive suite a few days before the World Trade Center came tumbling down.
What began as a last minute concept for the 2002 North American International Auto Show breathed life as if by divine intervention. Rather than build the push toy the boss had conceived, Engineering Executive Mark Reuss and project manager Mike Lyons conspired to build a driveable prototype … in about 100 days.
After enthusiast magazines raved and show goers mailed deposit checks, GM knew it faced a daunting challenge: converting Lutz’s brilliant concept into a hot Pontiac with profit potential.
Enter Lori Queen, GM’s vehicle line executive for small cars and Doug Parks, the Solstice’s chief engineer. “We began studying how to build Solstice soon after its show debut,” Parks recalls. “One early idea became known as ‘Delta with a tunnel.’ [GM’s Delta platform underpins the current Saturn Ion and the coming Chevrolet Cobalt.]
“The hope was to save investment costs by building Solstice on the same line that manufactures volume models. Unfortunately, by the time you add a tunnel and factor in the changes necessary to convert a transverse front-drive car into a longitudinal rear-driver, costs rise. It became clear that a modified Delta wouldn’t work so we began investigating a new architecture.
|The 2.4L Ecotec 4-cylinder engine (top) was switched from front to rear drive without any engine block modifications needed. The stamped-steel center tunnel (below) is reinforced with hydroformed tubes. The front-of-dash and windshield frame are built up as a subassembly and mated to the unibody with adhesives and a few welds, a technique developed for the Corvette. The rear differential (bottom) is from the Cadillac CTS.|
The challenge was finding a low investment approach that would enable a 20,000 units per year program to make money.”
Complicating matters were natural forces within GM to make Solstice longer, shorter, wider, and taller in hopes of stretching the platform’s potential. Variations on the theme were examined and presented to upper management in pursuit of a green light for production.
But the reactions of Lutz and GM President Gary Cowger surprised the investigation team. Parks explains, “They said ‘Wait a minute guys. All these variations, which are close but not the same, don’t look any better than the show car. And from an engineering standpoint, they aren’t any better. Furthermore, there’s no problem packaging the necessary components.’
Collectively we agreed that the original concept was a fantastic accomplishment that had earned GM heaps of praise and there was no good reason to mess with that success. So we decided to simply nail the show car.”
Queen explains that Solstice couldn’t have progressed in a timely manner were it not for the engineering integration that GM has achieved during the last five years, “Our most notable strength is our size. But GM’s dilemma has always been leveraging that size to our advantage.
“Thanks to recent reorganizations, GM now has a global linkage through system management teams (SMTs) that are knowledgeable about components available all over the world. Since we have a vast reservoir of parts bins to draw from, we began creating the new Kappa architecture by asking the SMTs to identify GM components most suitable for this small rear-drive application. Immediately, we found seats from the Opel Corsa and a suitable differential from the Cadillac CTS. If it’s already tooled, we know all the pros and cons of a particular part and its history.”
Parks adds, “Not having to engineer an engine, transmission, instrument cluster, or the car’s electronics saves a lot of time. The brakes and suspension knuckles are also reused.”
According to Queen, the goal was to chop the normal vehicle development process in half. “We used math everywhere we possibly could and built only a few physical properties. When possible, we went straight to production tools and built vehicles in the assembly plant. The whole development process was re-written and the critical path was changed. To go fast we took some risks. But we found our math capabilities are astounding and they did an excellent job of predicting how the hardware would perform.” Parks adds, “The cars have been designed, released, and we’re building production tools without a crash test. Instead we’ve gone through hundreds of computer simulations. If we find it necessary to tune the crash pulse, we have plenty of time to accomplish that by altering production tools.”
“Changing the critical path and relying heavily on math data allowed us to trim the normal 42-month process to 28 months,” beams Queen.
A speedy development process was just one means of keeping the price below $20,000 for a Pontiac steeped in sex appeal and sporty performance.
Parks explains, “While Solstice was still in the advanced investigation phase, we examined several attractive technologies such as one magnesium casting to serve as the entire front of dash, a composite center tunnel framed by four tubes, and a hydroformed windshield header.
“While the potential for lowering investment was good, some of these approaches posed a high risk. What was lacking was a proven strategy that could tie the components together with the desired dimensional accuracy. That risk inhibited our ability to go fast with this program.
“Even though the design evolved into a more conventional approach, we kept a structure that’s primarily MIG-welded hydroformed tubes. And some of Kappa’s makeup still falls under the heading of high risk.”
The key structural elements are a pair of hydroformed tubes that run bumper to bumper. Two additional hydroformed tubes define the bottom corners of the driveline tunnel.
The four tubes attach to transversely oriented stamped panels via MIG welds. The floor and tunnel are also ordinary stampings spot welded together and then bonded with adhesives to the structural framework.
Using a technique developed for the Corvette, the front-of-dash and windshield frame are built up as a subassembly and then mated to the rest of the unibody with adhesives and a few welds. Bumpers and the instrument panel support beam are roll formed.
Parks continues, “The more traditional approach cut risk and saved engineering time though it did increase the investments necessary for more stamping dies. That said, the hydroformed tubes we incorporated are far less expensive than a conventional body’s construction because they integrate several parts, thereby eliminating numerous welding fixtures and assembly tools.”
That in turn changes how Solstice will be manufactured. Notes Queen, “Solstice’s unique construction and low volume results in a body shop that looks nothing like those that use GM’s standard bill of process. Instead of having robogates clamp everything together in a fixture prior to welding, we’ll have smaller fixtures that set the dimensional accuracy piece-by-piece. Some of the MIG welding is automatic but most of it will be done by hand.
“The amount of work necessary to build this car in just a few stations is significantly less than what’s necessary for a conventional body. There aren’t that many welds because adhesives and fasteners are also used to join parts.
While hydroformed tubes are commonplace in body-on-frame applications such as full-size trucks and the Corvette, Kappa brings a new twist to body making called sheet hydroforming. While this technology is rare in the car business, it’s been in wide industrial use for decades.
Chances are your notebook computer’s case or the stainless steel sink in your kitchen was made by this method. According to Al Houchens, GM’s director of advanced manufacturing technology productionizing, sheet hydroforming delivers several benefits:
- A 10-50-percent tooling-cost savings.
- The ability to draw deeper-section panels with more complex shapes than is practical with conventional processes.
- Superior finish quality since there is no skidding friction or metal-to-metal contact on the visible surface.
- Added stiffness achieved by hydroforming’s more equitable spread of strain over the panel’s entire surface, improving dent and oil canning resistance.
|Solstice production begins in the summer of 2005. |
The one notable negative is a cycle time three to 10 times longer than conventional matched-die stamping. That’s a show stopper with high volume models such as the Chevrolet Cobalt but not a concern when the sales target is 20,000 or so sports cars per year.
The entire skin of the Solstice and mating inner panels — about ten parts in all — will be made by sheet hydroforming. Elated with this breakthrough approach, Queen exclaims, “We considered SMC and other composites but plastics drove investment and piece costs too high for a low-volume, low-cost car. And the beauty of sheet hydroforming is its ability to produce a hood with shapes, forms, and radii that couldn’t be achieved with conventional stamping methods.
“What’s more, the Kappa architecture doesn’t preclude other technologies. There’s no reason we couldn’t use aluminum, SMC, or conventional pressed steel for another car sharing this architecture.”
Parks adds, “Substituting longer hydroformed structural rails gives us a longer wheelbase. The chassis is a suspension engineer’s dream with forged-aluminum control arms and coil-over dampers so there’s ample capacity for other family members.
“The beauty of the Ecotec engine is that, with turbocharging or supercharging, it’s capable of delivering 250 hp which would take us from seven seconds for the base car’s zero-to-sixty performance down to the five-second range. In other words, the 4-cylinder offers so much flexibility we see no need for a V-6.”
Two interesting reference points are the Mazda Miata’s current base price of $22,388 and its zero-to-sixty acceleration of eight+ seconds. Assuming Lutz’s dreams come true, the Pontiac Solstice will trounce this arch rival on sex appeal, price, and performance. What’s more, the new Kappa architecture uses advanced manufacturing methods to hike quality and cut cost.
What we have here is the old GM tiger trying on a new set of stripes. SOLSTICE STATS
|unibody consisting of hydroformed, roll formed, and stamped steel components joined by MIG welds, spot welds, and structural adhesives|
|front engine, rear drive|
|2.4L GM Ecotec DOHC 16-valve four-inline; 170 hp @ 6400 rpm, 170 lb.-ft. of torque @ 4400 rpm|
|Aisin MW5 5-speed manual, Hydra-matic 5L40E 5-speed automatic|
|Suspension (front and rear):|
|forged aluminum unequal-length control arms, monotube dampers, coil springs|
|hydraulic power-assisted rack-and-pinion|
|4-wheel disc with optional ABS|
|18x8.5-in. cast aluminum|
|157.2 in./71.6 in./50.2 in.|
|60.5 in./61.2 in.|
|0-60 mph acceleration:|
|approximately seven seconds|
|summer 2005 as a 2006 model|