Abstract: A resonance detection device is provided for detecting resonance in an exhaust passage of an automotive vehicle. The detection device employs a temperature sensor in combination with an arrangement which enables the sensor to be exposed to a flow of exhaust gas the temperature of which is different from the temperature of the bulk of the flow, when resonance occurs. In given embodiments the arrangement takes the form different diameter conduits and/or vessels, while others it takes the form of a heat exchange device which either heats or cools the gases, and which is disposed proximate the temperature sensor. When no resonance occurs in the passage, the output of the temperature sensor remains stable. When resonance occurs the fluid flow characteristics in the passage change in a manner wherein the gas which has been either heated or cooled by the heat exchange device is induced to flow against the temperature sensor.

Abstract: Rigid polyurethane foams are obtained by reacting an isocyanate-reactive component containing at least two isocyanate-reactive hydrogen atoms, having a molecular weight of from 32 to 10,000 or a mixture thereof, with a polyisocyanate composition comprising(a) 30 to 70 pbw of polymethylene polyphenyl polyisocyanate with an iscocyanate content of from 29 to 32%,(b) 30 to 70 pbw of a compound having 30 to 42% by weight isocyanate content obtained by reacting 2,4- and/or 2,6-tolylene diisocyanate with an active hydrogen containing compound, thereafter initiating a reaction in the presence of trimerization catalyst, if necessary diluted with 2,4- and/or 2,6-tolylene diisocyanate,(c) 0 to 30 pbw of other isocyanate compounds in the presence of water and/or organic blowing agents, catalysts and surfactants.