Abstract: Transducer housing for mounting in a port in an engine combustion chamber has a metal diaphragm exposed to the combustion gasses. The pressure of the combustion gasses is transferred through an aluminum coupling disc which deflects a simply supported beam member. The beam member is formed of refractory material having epitaxially grown crystalline piezoresistors formed on one surface of the beam member and connected in a bridge circuit and is secured to a ceramic mounting disc. The aluminum coupling disc has a relatively high coefficient of thermal expansion which maintains a preload on the beam member for improved accuracy in spite of the low thermal expansion of the ceramic mounting disc. In an alternate embodiment, an expansion ring made of a material having a relatively high coefficient of thermal expansion is used to support a mounting disc on which the beam member is supported.