The industry has concerntrated on the quality of combustion  which can be improved by the designs of internal combustion engines.

Further improvements have been achieved by catalytic after-burning devices (such as catalytic converters) and by the simple partial return of the exhaust gases into the combustion process (ERG).

Such devices are required by environmental legislation for vehicles in most countries in order to reach legal emission standards, and while they improve the emmissions these systems do nothing to address the two principles of combustion.