Glen Davis Posted August 28 Report Share Posted August 28 The manifold pressure in my 1989J model fluctuates. This is being displayed on a Garmin G3X. What might be causing this? No other anomalies on any other instruments or gauges. Quote Link to comment Share on other sites More sharing options...
IvanP Posted August 28 Report Share Posted August 28 12 minutes ago, Glen Davis said: The manifold pressure in my 1989J model fluctuates. This is being displayed on a Garmin G3X. What might be causing this? No other anomalies on any other instruments or gauges. Can you identify any patterns of this indicated fluctuation? Do you have a secondary MAP indicator for reference? It could be some interference with the sensor data transmission that could cause the indication to fluctuate when, in fact, your MAP may not. I have exprienced similar situation with JPI 900 - my MAP indication on the JPI goes up every time I transmit on the radio. The old fashioned MAP gauge next to the JPI is rock steady. After spending quite a bit of time on troubleshooting, adding shielding to wires, etc., to no avail, I gave up and learned to live with this little gremlin. Quote Link to comment Share on other sites More sharing options...
Will.iam Posted August 28 Report Share Posted August 28 19 minutes ago, Glen Davis said: The manifold pressure in my 1989J model fluctuates. This is being displayed on a Garmin G3X. What might be causing this? No other anomalies on any other instruments or gauges. Fluctuates all the time, at idle, at full power? if all the time i would suspect a ground issue first. Quote Link to comment Share on other sites More sharing options...
Skates97 Posted August 28 Report Share Posted August 28 If it is a constant fluctuation of 0.5 you may need a snubber in the line. The electronics are much more sensitive to minor fluctuations than the old gages. 2 Quote Link to comment Share on other sites More sharing options...
201Mooniac Posted August 28 Report Share Posted August 28 As Richard points out, it could be needing a snubber, many who go to electronic instrumentation find they need it. If so, let me know, I have one or two around. Quote Link to comment Share on other sites More sharing options...
TheAv8r Posted August 28 Report Share Posted August 28 36 minutes ago, Skates97 said: If it is a constant fluctuation of 0.5 you may need a snubber in the line. The electronics are much more sensitive to minor fluctuations than the old gages. +1 this fixed it for my 930. 1 Quote Link to comment Share on other sites More sharing options...
shawnd Posted August 29 Report Share Posted August 29 Isn't the software supposed to compensate for the fluctuations / pulsing of air to the sensors? Wondering why Garmin doesn't just indicate this in their installation manuals. Quote Link to comment Share on other sites More sharing options...
Ragsf15e Posted August 30 Report Share Posted August 30 15 hours ago, shawnd said: Isn't the software supposed to compensate for the fluctuations / pulsing of air to the sensors? Wondering why Garmin doesn't just indicate this in their installation manuals. You would think, but the first thing JPI recommended to me was a snubber. I think it’s an Omega 8g but you better check sizing. Mine fixed my 930. Easy to install too. Quote Link to comment Share on other sites More sharing options...
Skates97 Posted August 30 Report Share Posted August 30 As @Ragsf15esaid, yes it should and they said it did as of some version update. Mine was a newer version of the software than the one that supposedly fixed it. Still had that constant fluctuation but the snubber did the trick. 1 Quote Link to comment Share on other sites More sharing options...
Ragsf15e Posted August 30 Report Share Posted August 30 10 minutes ago, Skates97 said: As @Ragsf15esaid, yes it should and they said it did as of some version update. Mine was a newer version of the software than the one that supposedly fixed it. Still had that constant fluctuation but the snubber did the trick. Yeah, mine is updated sw as well. Weird how it’s “not solvable” by sw. I’d think it would be pretty straightforward. 1 Quote Link to comment Share on other sites More sharing options...
shawnd Posted August 30 Report Share Posted August 30 Yeah, in the worst case, I would say an intro interview coding question of moving averages can resolve the issue "through software". 1 Quote Link to comment Share on other sites More sharing options...
A64Pilot Posted August 30 Report Share Posted August 30 On 8/29/2024 at 4:41 AM, shawnd said: Isn't the software supposed to compensate for the fluctuations / pulsing of air to the sensors? Wondering why Garmin doesn't just indicate this in their installation manuals. Some do, some don’t Electronics International does, I believe they call it “smoothing”. Piper on their turbines the gauges have a “snap” function I was told, when they get to normal, they snap into a reading and stop wandering around. Without something digital gauges last digit would often be a 8 which is what you get from rapid tiny fluctuations. Quote Link to comment Share on other sites More sharing options...
jetdriven Posted August 31 Report Share Posted August 31 We put a snubber on a MVP50 fuel pressure and it damped it right out. It previously was always all over the place. Quote Link to comment Share on other sites More sharing options...
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