Regarding the subject, Stan Evil post pretty much describe it. As far as I remember the max MAP on the PA34-200T was 40" (overboost light came on at 39,7") and the overboost valves opened at around 43" and the engines was allowed to run at 42" for max 10 sek, allthough 40" was SOP.
A wastegate is basicly a little piston that is controlled by a pin. There is a little pipe on the pressure side of the intakemanifold. This pipe end up in a regulator which is more or less a little
cylinder. The increase in press push this piston in and the piston is conected to a pin that regulate the piston in the waste gate, which bypasses a certan amount of exhaust around the turbocharger. When more press is required a spring draws the piston in the regulator back, causing the piston in the wastegate to close and more exhaust will come through the turbine, causing more press which again push the piston in the regulator, which again causes the piston in the wastegate to open and so on. Since this system is sensitive to wear, my personal belive is that continental have chosen to keep it simple an just fitted a overboost valve.
[This message has been edited by Danish Pilot (edited 05 May 2001).]