Abstract: An air-fuel ratio detecting device with which the air-fuel ratio can be accurately detected over the entire range of ratios, both for the lean range and for the rich range. An oxygen pumping element and an oxygen sensing element are arranged opposite one another with a gap therebetween and are disposed in a chamber in which exhaust gas flows. A signal which is symmetric in lean and rich regions is thereby obtained, and this signal is divided into separate portions in the two regions, which are then composed to obtain a single-valued signal accurately representing the air-fuel ratio over the entire operating range.

Abstract: A turbocharging system for an internal combustion engine improves performance and efficiency under low-speed, high-load operating conditions by adding secondary air to the exhaust gas upstream of the turbocharger. The secondary air combusts with unburned fuel contained in the exhaust gas to increase the temperature and pressure of the exhaust gas driving the turbocharger. Secondary air is added only when the exhaust gas temperature is above a prescribed temperature and the air-fuel ratio of the exhaust gas is below a prescribed ratio.

Abstract: A device for detecting the concentration of oxygen in an automotive exhaust gas, particularly, an automotive exhaust gas containing lead, providing reliable operation for long operating periods. The device includes an oxygen-ion-conductive solid electrolyte positioned between the atmosphere and the gas to be measured, and electrodes made of an electroconductive material, one of which is located on the surface of the solid electrolyte contacted by the atmosphere and the other on the surface of the electrolyte contacted by the exhaust gas. The surface of the electrode in contact with the exhaust gas is coated with a protective, heat-resistive metal oxide layer having supported thereon a uniform layer of a lead-trapping thermally stable metal in a molar amount of 0.4% of the metal oxide.