Jetguy
Well Known Member
With a fixed pitch prop RPM is effected by air speed where as Manifold Pressure stays constant. On aircraft with constant speed prop you always have a Manifold Pressure gauge. When flying this is the instrument you use to set power and then adjust the controllable pitch prop (constant speed and controllable pitch prop are one in the same)for the desired RPM. (Just a refresher cause some RV12 owners have never flown a constant speed prop) Because speed on the RV12 causes the RPM to vary some what Manifold Pressure is a more accurate way to set your power for cruise. In ruff air where you are experiencing thermals and mountain wave action when the plane pitches up your airspeed decreases and then you RPM decreases and Vice versa. However like our oil pressure the Manifold Pressure, because of the way the Dynon sensor read it, varies +- 1 to 1.5 inches.
We discussed this with Dynon at OSH. Their tech guy suggested we put some kind of restriction in the line to reduce or dampen this fluctuation. So Colin removed the tube from the Dynon sensor and put a small amount of RTV in the tube then he inserted a sewing needle which was lubed so it wouldnt stick to the RTV and waited for it to dry. This didn't take long in temps here in Texas of 108F. Well it worked great no more fluctuation on the Manifold Pressure indication. I hated that fluctuation. So far we have managed to fix the indications on the oil pressure and now the Manifold Pressure. Next that pesky oil temp. IMOH just like the oil pressure because of where the oil temp sensor is located (out on the front of the engine) the vibration there is causing the oil temp sensor wire to vibrate on the sensor and cause fluctuation in the readings on the Dynon,not much but enough to notice.
We discussed this with Dynon at OSH. Their tech guy suggested we put some kind of restriction in the line to reduce or dampen this fluctuation. So Colin removed the tube from the Dynon sensor and put a small amount of RTV in the tube then he inserted a sewing needle which was lubed so it wouldnt stick to the RTV and waited for it to dry. This didn't take long in temps here in Texas of 108F. Well it worked great no more fluctuation on the Manifold Pressure indication. I hated that fluctuation. So far we have managed to fix the indications on the oil pressure and now the Manifold Pressure. Next that pesky oil temp. IMOH just like the oil pressure because of where the oil temp sensor is located (out on the front of the engine) the vibration there is causing the oil temp sensor wire to vibrate on the sensor and cause fluctuation in the readings on the Dynon,not much but enough to notice. 