DEARBORN, MI - As U.S. Big Three representatives provide updates of their ongoing Partnership for a New Generation of Vehicles (PNGV), or "Supercar," programs at the Environmental Vehicles '95 (EnV'95) conference here, it becomes increasingly apparent that ideas for development specifics are starting to converge.

Big Three officials tied to the hybrid electric vehicle (HEV) programs directed by the U.S. Department of Energy (DOE) confirm Supercar-type development efforts now are focusing on hybrids. This "focus-narrowing" follows a general timeline set by PNGV to have Supercar prototypes ready for testing by 1997-'98.

Absent from EnV'95 is any substantial representation from either Japanese automakers or suppliers. At least two executives from large U.S. suppliers say a race for environmental-vehicle development superiority may be shaping up between U.S./European interests and the Japanese.

Maurice Isaac, manager-automotive technical programs for General Electric Co., observes that "the Japanese tend to do their technical work at home while Americans and Europeans are more likely to work together. It may just be an accident of culture."

Others at EnV'95 aren't so sure. They believe the Japanese are miffed at their near-total exclusion from U.S.-oriented technology partnerships such as PNGV and the United States Council for Automotive Research (USCAR). Both organizations are limited to Big Three participation.

Politics aside, hybrid-vehicle project leaders from Ford Motor Co., General Motors Corp. and Chrysler Corp. essentially agree that - considering foreseeable technology applications - a vehicle that meets Supercar economy, performance and emissions targets must be an HEV.

Engineers developing drivetrains for the new cars also say their research will help near-term vehicle development, particularly in the areas of increasing fuel economy and decreasing emissions.

"CAFE (Corporate Average Fuel Economy) standards are here. They may get worse," says Gerald D. Skellenger, GM hybrid vehicles engineer. Mr. Skellenger says the near-term possibilities from Supercar development include a goal to achieve at least twice the fuel economy of current vehicles, and that those developments are critical to meeting potentially more demanding CAFE requirements.

To do that, hybrid-vehicle engineers have identified two crucial areas for development: increasing the efficiency of electric drives and optimizing the thermal efficiency of heat engines. But Mr. Skellenger stresses that developing just a high-efficiency electric drive or heat engine "isn't going to be enough, alone, to reach two-times (current) fuel economy."

And most agree that the "series" hybrid - one in which the heat engine generates only electricity to supply a traction motor or an energy storage device and is not directly linked to the driveline - appears to be the most practical hybrid arrangement.

In narrowing the possibilities for environmentally friendlier vehicles, and keeping in mind the main priorities of electric drive and heat engine optimization, hybrid development engineers have identified some technologies that have truly realistic near-term potential - and some that don't.

The winners:

* Direct-injected piston engines, particularly direct-injected diesels. In the conferences (and in the halls) of EnV'95, engineers once again spoke in excited tones about the diesel.

How can that be, given the diesel's rather unceremonious tar-'n-feathering following the early-'80s fuel crisis? GM's 1980 Cadillac Seville was the first American auto to feature a diesel engine as standard equipment, and diesel-powered Oldsmobiles were sold in large numbers. GM's diesels, along with most of its early-'80s contemporaries, formed the still simmering public perception that diesels are smelly, noisy, smoky, underpowered creatures that clatter, start hard and require hard-to-find fuel.

Although the fuel availability problem is not yet fully resolved, today's passenger-vehicle diesels are far removed from the ill-refined lumps of two decades ago. High-revving diesels - featuring both direct (in-cylinder) and indirect fuel injection - have been developed by some of the best names in the auto business: Mercedes-Benz AG, Volkswagen AG and VM Motori SpA. These diesels are quiet, almost clatter- and vibration-free and produce much less pollution.

Moreover, the diesel's inherent efficiency still is all but unchallenged. "Diesel is the mechanical equivalent of the fuel cell. That's where all the (engine development) effort should be spent right now," asserts GM's Larry J. Oswald, program manager-hybrid vehicle.

A BMW engineer concurs. "If the 2-stroke engine has a future, it is as a diesel. Efficiencies for a 2-stroke diesel are more than 50%," he says.

Ford's Ron I. Sims, manager-alternative power sources technology, is confident directed-injected diesels will enjoy strong consideration for HEV testing in the near future. Besides outstanding thermal efficiency, diesels' low overall emissions "profile" means less reliance on expensive, deterioration-prone exhaust aftertreatment strategies.

* Gas turbines. Several automakers and large suppliers are working overtime to prove out the advantages of new-technology turbines.

With efficiencies of 30% or better combined with predictions for extremely low emissions, HEV development engineers believe the simple, relatively lightweight turbine has a genuine future. Turbines are helped by the fact that they'll burn just about any fuel without any complex hardware requirements. And their compact dimensions could provide vehicle designers with some desirable powertrain packaging options.

Similarly, the EnV'95 conference proceedings indicate that some Supercar technologies being researched may need more time to "mature."

* Electric vehicles. Despite all the claims for new-age batteries, Ford's Mr. Sims emphasizes that there currently are only three commercially available electric-vehicle (EV) battery technologies: lead-acid; nickel-cadmium and nickel-iron. Other technologies, though promising, for one reason or another aren't yet commercially viable.

One engineer, who spoke separately with Ward's Auto World, says the potential of "pure" EVs to be a Supercar-like vehicles is practically nil. "Look," he says, "forget EVs. They're never going to make it because there just aren't good enough batteries; if you look at the energy density in a gallon of gasoline and the energy density in the best batteries available, it's crystal clear.

"We may get batteries in the near-term that make purpose-built EVs something of a possibility," he continues, "but there may never be batteries capable of running a Supercar-type vehicle (Taurus/Lumina size; seating for five; 0-60 mph [0-97 km/h] in 11 seconds) at the performance and distance standards PNGV has set forth."

Still, former GM Chairman Robert C. Stempel and the folks behind the GM/Energy Conversion Devices (Ovonics Battery Co.) joint venture to produce the promising nickel-metal hydride EV battery believe nickel-metal hydride (NiMh) technology is poised to make long-distance EVs a reality. They say their batteries will be ready for EVs by sometime next year - two years ahead of California's ZEV (zero emissions vehicle) mandate.

Others believe it's not the batteries, but instead the lack of a cohesive EV infrastructure that ultimately limits EVs to "cult" status.

* Two-stroke engines. The debate rages - and we're a tad exhausted by it all. Big Three hybrid experts - admittedly studying "alternative" reciprocating engines intently - are nonetheless reluctant to comment on the 2-stroke. One finally admits, however, that "looking at (emissions standards requiring) 0.04 grams/mile of unburned fuel in a ported engine is difficult."

* Fuel cells. Many believe fuel cells have potential, although not right now. Ford's Mr. Sims says the fuel cell's prime feature is its complete non-polluting operation and an ability to deliver high power levels over a wide range of operating conditions.

But fuel cells now in the prototype stage are heavy and bulky, not the sort of thing one wants for a weight- and size-optimized vehicle. Moreover, a fuel cell currently costs $3,000 per kilowatt-hour of energy produced; experts say that figure has to be reduced by a factor of 100.

* Alternative fuels. Consumer studies conducted by Ford indicate that consumers are extremely reluctant to relinquish the freedom gasoline's ubiquitous availability allows. The company's research says fully 90% want something, regardless of what type of drivetrain it's carrying, that runs on gasoline (or at least diesel).

Gas is sold everywhere, prompting one alternative-fuels critic to observe: "Try for a week, just one week, when you need gas to not fill up until you find a station that also offers an alternative fuel like compressed natural gas (CNG) or liquefied propane gas (LPG). Chances are you'll panic and give up as the gas-gauge needle drops toward empty."

Says a GM source: "We (hybrid-vehicle developers) cannot exclude alternative fuels. But we have to get these things (HEVs) started in the market." So if the public first has to be conditioned to accept HEVs, then the auto industry has no intention of also asking them to then seek out alternative fuels.

There's one concession to alternative fuels, though: HEVs will be "ready" for them when the alternative-fuel infrastructure is ready. Some $2-million funding recently announced by the DOE to expand alternative-fuel programs in 19 states may begin to address the "readiness" issue.

EnV'95 shows that Detroit automakers (and some of their European counterparts) and larger suppliers have studied myriad HEV and Supercar powertrain possibilities that exist and have begun to develop cohesive plans for the next step in creating high-mileage, low-emitting vehicles.

For now, it appears they primarily agree: The HEV or Supercar for the near future will be a hybrid electric with some sort of heat engine, fueled by reformulated gasoline or diesel.