Hi everyone. I have a strange manifold pressure sensor indication that's just started in the last couple of flights.
After takeoff, I reduce my manifold pressure to 25", which I then maintain as long as possible during climb by adding throttle (if I don't, of course, the pressure drops as I gain altitude). However, lately, I see my manifold pressure *rising* as I climb, even without adding throttle, which makes no sense if things were working as they should. On my latest flight, right after reaching 10000', wide open throttle was showing around 26" initially, though in my experience, it should be closer to around 20".
Over the course of 10 or so minutes, the indicated pressure slowly reduces to what it should be reading.
When I change throttle, the indicated manifold pressure changes quickly, and as expected, so my first thought isn't necessarily blockage in the tube running from the engine to the sensor. I've just seen (so far) that during a climb (and presumably during a descent, though I haven't tested this), the indication is unreliable until levelled off for several minutes. Is there a vent on the sensor to outside air that may be partially blocked? Or equivalently, is there a fixed pressure chamber in the sensor that should be holding a constant pressure but is leaking to ambient?
Obviously, I can just replace the sensor and I expect the problem would go away. But I'm trying to understand what might cause this (and if it's just possibly a partially blocked vent hole, it may be easy enough to just clean out).
Thanks for any suggestions!
Dan
After takeoff, I reduce my manifold pressure to 25", which I then maintain as long as possible during climb by adding throttle (if I don't, of course, the pressure drops as I gain altitude). However, lately, I see my manifold pressure *rising* as I climb, even without adding throttle, which makes no sense if things were working as they should. On my latest flight, right after reaching 10000', wide open throttle was showing around 26" initially, though in my experience, it should be closer to around 20".
Over the course of 10 or so minutes, the indicated pressure slowly reduces to what it should be reading.
When I change throttle, the indicated manifold pressure changes quickly, and as expected, so my first thought isn't necessarily blockage in the tube running from the engine to the sensor. I've just seen (so far) that during a climb (and presumably during a descent, though I haven't tested this), the indication is unreliable until levelled off for several minutes. Is there a vent on the sensor to outside air that may be partially blocked? Or equivalently, is there a fixed pressure chamber in the sensor that should be holding a constant pressure but is leaking to ambient?
Obviously, I can just replace the sensor and I expect the problem would go away. But I'm trying to understand what might cause this (and if it's just possibly a partially blocked vent hole, it may be easy enough to just clean out).
Thanks for any suggestions!
Dan