With the modified exhaust-gas recirculation, boost pressure, and nozzle configuration, the TUM engine almost meets European emissions standards scheduled to take effect by 2014. Those standards stipulate that a heavy-truck diesel engine can emit only five milligrams of soot particles and 80 milligrams of nitrogen oxides per kilometer. Wachtmeister says that the TUM test engine met the nitrogen-oxide limits with "no problem" and is "very close" to the soot limits.

George Anitescu, a researcher at Syracuse University, is skeptical about the project's practicality. "The research may solve, somewhat, the trade-off between particulate matter and nitrogen-oxide formation" inherent to diesel combustion, he says. But he thinks the energy needed to achieve the high pressures used will decrease the engine's efficiency. Another concern, he says, is finding materials--particularly affordable ones--that can withstand the extreme pressures.

"For the time being, turning this design into a production engine is not practical," admits Wachtmeister. The TUM Internal Combustion Engines Workshop had to specially produce 95 of the components for the test engine. However, using these special components, the team was able to successfully apply the modifications to a production truck engine.

Wachtmeister expects that it will take between five and 10 years to come up with solutions that will allow the production of engines reliable enough to run for hundreds of thousands of kilometers without failing. The turbocharger and fuel-injection system will be particularly challenging to adapt for either heavy-duty trucks or car engines.

In the meantime, he says, the design could easily be implemented today in certain industrial engines such as diesel generators, the most common type used in standby and emergency power systems. And, Wachtmeister says, automotive companies in both Germany and Japan have expressed interest in the technology.