Ed_Wischmeyer
Well Known Member
In the five years I've had the RV-9A (third owner, O-320, carbureted), the manifold pressure readout (Garmin G3X Touch) has had an annoying tendency -- it lags the the throttle position. For example, reducing manifold pressure from cruise to 18", pull the throttle back to see 18", increase the friction so that the throttle doesn't creep. A few seconds later, it will read 16" or 16.5" or something.
We thought it was the restrictor at the manifold, or maybe the line between the manifold and the sensor was clogged, or... At the last annual, all of the old rubber engine tubes were replaced, so we did the manifold pressure line, too. When we took off the old line, we discovered there was NO restrictor. We put one in and put in the new line. No change.
So maybe it's the sensor. Stein had one, mercifully, and I swapped it in this morning. No change. (The old sensor has maybe 600 hours on it, apparently works as well as the new one, so if you need one, let me know.)
Another trait when I got the airplane, and I guess I just ignore it these days -- not sure if it's still there or not -- is the the manifold pressure wanders by +/- an inch in cruise. It's pretty obvious in the digital data.
The only other thing I can think of is that there is heavy filtering in the G3X Touch to reduce sensor noise...
Anybody else see this phenomenon? My old Cessna with 180 HP and analog gauge didn't do this...
We thought it was the restrictor at the manifold, or maybe the line between the manifold and the sensor was clogged, or... At the last annual, all of the old rubber engine tubes were replaced, so we did the manifold pressure line, too. When we took off the old line, we discovered there was NO restrictor. We put one in and put in the new line. No change.
So maybe it's the sensor. Stein had one, mercifully, and I swapped it in this morning. No change. (The old sensor has maybe 600 hours on it, apparently works as well as the new one, so if you need one, let me know.)
Another trait when I got the airplane, and I guess I just ignore it these days -- not sure if it's still there or not -- is the the manifold pressure wanders by +/- an inch in cruise. It's pretty obvious in the digital data.
The only other thing I can think of is that there is heavy filtering in the G3X Touch to reduce sensor noise...
Anybody else see this phenomenon? My old Cessna with 180 HP and analog gauge didn't do this...