Valves are electronically controlled with variable operation. A pressure sensor measures the pressure drop across the valve opening to verify that the EGR flow rate is correct. In the catalytic-converter system, the exhaust gas, which must have a certain oxygen content, is passed over a bed of metal maintained at high temperature. The sensor unit and the electronic interface will be incorporated right into the spark plug. Major new developments in antipollution car sensors will most likely center on optimizing existing systems rather than breaking new ground.
Many experts feel that the theoretical minimum emissions levels are being approached.
The above was adapted from an article by Greg Paula, Associate Editor. The full text may be found in the November 1996 issue of Mechanical Engineering magazine. To obtain a copy of this issue, click here .