Under the Hood of the 1999 Saturn
In March 1988, the first production equipment arrived in the buildings in-progress on the Spring Hill, Tennessee, site that is Saturn Corporation. On July 11, 1988, these machines were up and running in the Powertrain Building.
More than a year later, on November 1, 1989, the first Saturn engine was produced. (The first car rolled off the line on July 30, 1990.)
The die casting in powertrain of such things as transmission cases is pretty straight-forward and common. But the manufacture of engine blocks, heads and other components, even today, remains unique among auto manufacturers. That's because Saturn's aluminum blocks and heads are made with the lost-foam casting process. Simply, this process involves using a polystyrene material for the patterns. A big benefit of this is that the parts can be cast with much more detail than is possible with alternative casting approaches. Consequently, the parts are more near-net shape. Which means that there is less machining that needs to be performed on the parts—less drilling, milling, etc.
Perhaps it is a result of the fact that Saturn Powertrain was a greenfield site (literally and figuratively) that it was possible for them to use what was considered then—and to a certain extent, now—a rather radical approach to engine manufacture. That is, most engine plants have a considerable investment in conventional casting approaches; consequently, to move to lost-foam would be a huge investment, even though the process does eliminate the need for some post-casting machining equipment.
But there are some inherent limitations in the lost-foam approach. For example, like all aluminum auto engines, it is necessary to use cast iron liners in the cylinder bores of the Saturn 1.9-liter engines (there are single- and dual-overhead cam configurations). Chrysler, for one, is utilizing a process for its 3.5-liter V6s (used in the LHS and 300M) that has the cast iron sleeves cast right into the aluminum block; it's done in one. But because of the lost-foam approach, the cast iron sleeves must be inserted into the Saturn engines after the block has been made—so while there is some process minimization on the one hand due to the near-net casting, there is some additional work that needs to be done (liner insertion), on the other.
GM researchers are checking out some processing alternatives that may be beneficial, however. For example, the plasma source ion implantation process (GM is calling its approach IONCLAD) allows aluminum pistons to be treated with a diamond-like carbon coating. Which—assuming that the tests prove that this can be performed economically and reliably—would be a natural for use in the Saturn power plants. So it may be back to "score one for Saturn" in this regard, as it would eliminate the need for a liner of any type.
For the past several years, the automotive consumer press has complained that theSaturn engines are too noisy. So, for the 1999 model Saturns, product and process engineers at Saturn have taken this criticism to heart and worked at developing fundamental fixes that would silence the critics. This is actually a case of considerable continuous improvement, because the extent of the changes are such that Richard P. Andersen, Product Engineering manager, Powertrain, suggests that it would have been appropriate to consider the present engine to be a new product as approximately one-third of the parts in the engine have been changed for the '99 model. Karen Lewis, Powertrain's future model year coordinator, remarks, "This is the biggest change for powertrain since the initial launch."
The changes include a redesign of the block. One of the efforts made was to increase the structure, so ribbing was added to the side of the block (actually, this was one of the first steps taken to improve the powertrain; it occurred in the '98 model). The lost-foam casting process facilitated making the modification in a cost-effective manner.
The aluminum pistons, which are produced for Saturn by Kolbenschmidt, have undergone a modification, with a redesign of the head profile to make it smaller than the previous piston. Also, a molybdenum coating is applied to the piston to help decrease friction.
There is a significant change in the connecting rod. It is now a powdered metal, near-net shape forging. The centerline of the connecting rod has been moved 3.5 mm, which changes the kinematics of the system, helping reduce forces, thereby helping to minimize noise.
The crankshafts, which are also made with lost-foam, have been modified through the addition of four counterweights, which now bring the total to eight. The benefit here is better balance. Given that the crankshaft accounts for about two-thirds of the vibrations in an engine, this is of considerable help to the mission to reduce noise.
The DOHC head was significantly modified so that there is a size reduction of 30 mm across the front.
According to Andersen, the overall 1999 engine is slightly heavier than its predecessor. Specifically:
|•Con rod:||-0.1 kg|
|•Head (DOHC)||-1.9 kg|
Which provides an overall weight increase of 2.6 kg. While that may seem counter with regard to efforts to lighten things up wherever possible for the sake of fuel economy, they have been able to reach their noise reduction targets while—at least in the case of the DOHC engines—being able to increase miles per gallon by at least one in both city and highway driving. This is due, in large part, to the utilization of a pivoting roller rocker system for the camshaft and the valves in place of a direct-acting setup. Due to the decrease in friction that it provides, there is a fuel economy improvement.
Asked to survey what he knows of with regard to engine technology both within Saturn and without, Andersen says that there are no huge changes that he's aware of when it comes to materials for engine applications. He comments that people are starting to look at ceramics again. But overall, it seems that aluminum and cast iron will hold sway for the foreseeable future.
What Really Matters
What are you trying to accomplish?
That, fundamentally, is the question that Tom Denning, vice president, Manufacturing, Saturn, thinks managers at manufacturing companies need to ask, then determine what steps are necessary to achieve that goal.
Denning explains that there is sometimes a situation when people do benchmarking and discover that, say, Toyota is good at this, Honda is good at that, Chrysler is good at something else, and so on. Or The Harbour Report is in hand, and it indicates who is doing what well.
Then there is a tendency for there to be a drive to meet those marks (or marquees).
But Denning points out that what really needs to be done is for an organization to assess what is internally important, then concentrate on improving those areas. Going after the other things may simply be distracting or not fundamentally useful for achieving the goal. "Do you think Mark McGuire is concerned about the record for stolen bases?" Denning asks rhetorically, when the slugger, just after the mid-season break, was at 40 runs.
Focus on what's important. If there's a benchmark that has 72 items on it, it probably isn't worthwhile to pursue number 72 (or maybe anything after 10) unless it is a metric of critical competency.
In the case of Saturn, Denning says, the goal is to build a reliable, functional vehicle that customers will acknowledge represent good value. He knows that it is not going to be perceived as having avant garde styling, for example, but he also knows that continuous improvement in building the cars can help Saturn reach the reliability measures that they are working toward. That's what's important to them.
In order to do a better job of producing vehicles, not only must there be a recognition of what's important and a means put in place by which that can be achieved, but there needs to be an examination of the entire system: design through production. There can't be a situation where an organization makes a hand-off, as in "You deal with it."
Which sounds like simultaneous engineering.
"That's right," Denning says. "But there is still too much sequential work going on in industry today."
So pick your spots. Then cross functionally work to accomplish those goals.
If Mark McGuire were to get the most stolen bases this season, he'd undoubtedly be pleased. But clearly, his focus is on accomplishing another goal. Which is what really matters.
Why Midsize & Not Sport Ute?
Next year, the Saturn franchise will be getting a new car, the midsize L-Series, which will be built in a plant in Wilmington, Delaware.
Don Hudler, Saturn chairman and president, admits that the popularity of trucks and sport utility vehicles "has made our job more challenging during the last two years." That's because, of course, Saturn has a small coupe, a small wagon, and a small sedan. No truck. No sport ute.
Which might lead to a bit of wonderment about the first sentence: Why a big(ger) sedan?
Hudler answers that when they began looking at expansion plans in 1995, they determined that the sport ute segment offered an opportunity on the order of 60,000 to 70,000 units. But midsize could mean 200,000 units per year. That latter number would effectively double the size of the output of the company.
"If we had to make the decision again," Hudler says, "we'd make the same one."
According to a knowledgeable industry analyst, there is a sport ute in Saturn's future, however.