MP increase

[Richard]

Why?

RE:
1979 Cesnna T207A
Continental TSIO-520-M
McCauley D3A34C401/90DFA-10 3 blade
Western Skyways O/H 1700 hours (300 TBO)
TTE unknown

Why would a constant power descent from 5,500 msl to 5,000 msl result in a 2" increase in manifold pressure? Power setting is 26" MP 2300 RPM.
MP increase remains after airspeed stabilizes at new altitude.

2nd Q: (This is my shot in the dark question) Would blockage or leak in engine induction air contribute to MP increase?

 

[Walt]

Turbo wastegate angle is set by the absolute pressure controller. You might determine how long it has been since it (controller) was overhauled and also check the critical altitude per the maintenance manual. It has been I while since I flew a T-210, but the POH may give more information.
Walt

 

[Richard]

Controller was replaced 17 hours ago. The MP increase preceeds and continues after that mx.

 

[Walt]

If your mechanic knows the system well and is happy I would adjust the throttle to set the power. This is the kind of problem you could spend a lot of money on and not get satisfaction. I had a similar problem and decided after a lot of screwing around that those controllers are not that accurate over a wide range of altitudes and power settings.
Walt