ESX Education

Automotive Industries,  April, 2000  by Gerry Kobe

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DaimlerChrysler's ESX3 schools the PNGV program on how to make 80-mpg family cars affordable.

The most important thing about DaimlerChrysler's ESX3 is not its 72-mpg (gasoline equivalent) diesel/electric hybrid powertrain. Nor is it the car's advanced lithium ion battery pack, injection-molded thermoplastic body or even its ultra-trick elastomeric rear suspension. The real key to ESX3 is how its design, engineering and materials have dropped the cost of the company's latest PNGV concept into striking distance of an affordable car.

To its credit, DaimlerChrysler has discussed the cost bogies of its Partnership of a New Generation of Vehicles program right from the beginning. In 1996 company officials estimated the first ESX, an aluminum-intensive, Intrepid-based hybrid concept, would cost a prohibitive $60,000 more than a conventionally powered car, if built. Two years later, the plastic-bodied ESX2 slashed that cost penalty to $15,000. The new ESX3 carries a mere $7,500 premium, the company estimates. Of that premium, 70 percent is in the diesel/electric hybrid powertrain; 20 percent is in the lightweight chassis; 15 percent is in the electrical system, 10 percent is in the body.

While that tallies up to 115 percent, Chrysler officials claim that ESX3's body structure will save 15 percent cost, compared to the current steel-bodied Intrepid, if labor in stamping and paint is included. And further cost reductions are in the works. Projections for volume production cars in 2004 show costs dropping to within $3,000 of a gasoline powered Intrepid.

Indeed, philosophies at DC are different than either General Motors' or Ford's approaches to PNGV (see AI, January 2000, p.23). GM's Precept is a hotbed of pricey technology, high cost materials and bizarre, but aerodynamically efficient styling. Ford's Prodigy, on the other hand, looks almost blandly conventional, but still bears the price of its aluminum body/chassis.

In contrast, ESX3 wears angular and aggressive styling (think future 300M) that's meant to appeal to a mass market. In fact, the car's form is intentionally less aerodynamic than ESX2 (0.22 Cd versus 0.19), to eliminate the "futuristic concept car" look that could potentially turn off buyers.

Plastic Body R&D Continues

To help "fund" the mechanical technology in ESX3, DC continues to embrace the idea of a lightweight, injection-molded thermoplastic body -- a process it developed for its CCV program. And more recently, the company further validated its belief in this technology when it announced it will be used for mass production on MY2001 Jeep Wrangler hardtops (see AI, January 2000, p.29). Note, however, that ESX3 itself is not injection molded. It is a hand-built fiberglass bodied proof-of-concept car, designed to signal DC's intended production methods.

Larry Oswald, director of body engineering at DC's Liberty and Technical Affairs group, says the injection molding technique intended for ESX3 can pull 15 percent out of the cost of making a vehicle body, perhaps even more if some technical hurdles are cleared.

"Right now we still put some metal into our plastic structures," Oswald says. "But we are getting less and less as we learn to put the vehicles together. We probably can't do a plastic unibody yet, but we are working towards it. Currently, it's impossible to carry all the suspension loads and powertrain loads directly into the plastic without driving the cost of the composite sky high. Those plastics cost six or seven dollars a pound and that defeats our cost advantage."

For now, ESX3 is designed to use what Oswald's team jokingly dubs an aluminum "sparseframe" inside the thermoplastic, inner and outer body side rings. This same approach was taken with second-generation CCV vehicles to help them meet rollover standards. However, Oswald says that by designing more hollow sections into plastic structures, as well as the use of structural foams and/or cellular reinforcing materials, metals could be eliminated.

The low-cost body in ESX3 helps make up for other expensive technologies, such as the hybrid drivetrain. It features a 1.5L, three-cylinder, common rail diesel from Detroit Diesel, linked with a Delphi-developed 15 kW electric traction motor. The motor supplies extra power during hard acceleration and also serves to "hot start" the engine, which shuts down when the vehicle comes to a stop.

An even lighter, more efficient 1.3L turbodiesel is being developed by Daimler-Benz for a future evolution of the ESX, say company officials.

The two power sources are mated to a six-speed automatic transmission that is claimed to have the efficiencies of a manual. The transmission is similar to what is used on DC's Smart Car, but refined for smoother shifts and no lag time during gear change. The unit has two separate clutches that ease the transition between gearchanges. In essence, two gearsets are engaged at all times and the clutches cycle on and off to facilitate change from one drive path to the other.