DETROIT - Probably the most intriguing display at the recent Global Powertrain Congress 2000 here is a new-century spin on an industrial-revolution antique: the steam engine.

Once or twice every decade, somebody revives the prospect of the steam engine for modern passenger vehicles. And once or twice every decade, those promoters quietly go away when questioned about overall efficiency; transferring energy from one medium to another - i.e. fossil fuel to water (steam) to mechanical work - involves unseemly thermal losses.

But Berlin's IAV, the developer of the ZEE (zero emissions engine), addresses efficiency and other issues in a head-on fashion. And in so doing, remains doggedly focused on the modern steam engine's most promising possibilities: easily attained Super Ultra Low Emissions Vehicle (SULEV) levels, good specific torque and fuel economy matching today's best diesels.

IAV assembled private and public support to develop its steam engine concept, and much of the initial work, according to IAV's literature, went toward defining the potential problems. From there, a single-cylinder prototype emerged as a study model.

Aside from increasing efficiency, the IAV developers focused on engine control for quick-changing load demands, new materials and sealing technologies that might be required, and how to lubricate such an engine.

IAV has forthrightly determined that a lot of work remains - but that the problems are not insurmountable. The single-cylinder prototype led to ZEE03, a 3-cyl., 2-stroke concept engine that develops 67 hp (50 kW) at 2,000 rpm (the developers admit that steam engines will not have a wide speed range) and a generous 221 lb.-ft. (300 Nm) of torque from 1L (992 cc) of displacement.

IAV says that packaging is critical, but is confident that "it is possible to integrate an advanced steam engine with its auxiliaries into the engine compartment of a (current production) compact car." The developers concede there are other nagging issues, including startup times (also a bugaboo for fuel cell vehicles) and keeping the onboard water supply from freezing in cold climates.

The surprisingly realistic assessment from its own developers has the modern day steam engine as a promising prospect, but one with numerous remaining developmental challenges. IAV says the funding for the steam engine project runs through 2001, and "at present we assume that development of the ZEE to readiness for series production will require a period of an additional five to seven years."

Hey, at least they're honest.