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Deems Davis
Joined: 09 Jan 2006
Posts: 925
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 Posted: Sun Nov 25, 2012 3:57 pm Post subject: Manifold Pressure 'excursions' Your feedback wanted |
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We just returned from a trip to Yosemite for Thanksgiving. On the return flight leaving Mariposa Airport, after pulling everything back to 25 Sq for climb, I had exited the pattern and established a climb (at) 105 kts when I noticed that the MP was reading 30 " !. My 1st reaction was that I must not have pulled the throttle back, but when I pulled the throttle back to 25" the fuel flow dropped to 10 gph, and the engine noise softened considerably. I increased the throttle back to where the fuel flow should have been for climb out and watched the MP slowly drop back to 'normal'. All other gauges appeared to be reading what I would expect them to be. I monitored everything closely for the next 30 mins and everything looked and acted 'normal'. About 1:30 into the flight everything was stable (at) 22" MP and 2350 RPM, and again the MP suddenly increased to 26". Again all other guages read normal, and no change in the sound of the engine. Once again the MP slowly decreased until it settled again (at) 22".
Does anybody have any similar experience or insight into what the root cause could be?
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Kelly McMullen
Joined: 16 Apr 2008
Posts: 1188
Location: Sun Lakes AZ
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| Posted: Sun Nov 25, 2012 4:13 pm Post subject: Manifold Pressure 'excursions' Your feedback wanted |
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Deems,
Sounds like you have a fitting coming loose or other intermittent leak. MP will go up to ambient if the seal is broken on MP line.
Mariposa and Yosemite are great. We were there right after Labor Day.
On Sun, Nov 25, 2012 at 4:56 PM, Deems Davis <deemsdavis(at)cox.net (deemsdavis(at)cox.net)> wrote:
[quote] We just returned from a trip to Yosemite for Thanksgiving. On the return flight leaving Mariposa Airport, after pulling everything back to 25 Sq for climb, I had exited the pattern and established a climb (at) 105 kts when I noticed that the MP was reading 30 " !. My 1st reaction was that I must not have pulled the throttle back, but when I pulled the throttle back to 25" the fuel flow dropped to 10 gph, and the engine noise softened considerably. I increased the throttle back to where the fuel flow should have been for climb out and watched the MP slowly drop back to 'normal'. All other gauges appeared to be reading what I would expect them to be. I monitored everything closely for the next 30 mins and everything looked and acted 'normal'. About 1:30 into the flight everything was stable (at) 22" MP and 2350 RPM, and again the MP suddenly increased to 26". Again all other guages read normal, and no change in the sound of the engine. Once again the MP slowly decreased until it settled again (at) 22".
Does anybody have any similar experience or insight into what the root cause could be?
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dave.saylor.aircrafters(a
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| Posted: Sun Nov 25, 2012 4:16 pm Post subject: Manifold Pressure 'excursions' Your feedback wanted |
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Deems,
Could you have a leak in the sender line? Was the ambient pressure anywhere near 26" the second time? I would clean out and test the line to the MAP sensor. See if you can catch anything that comes out--just to see. If it seems perfectly clean then consider the sender. It doesn't sound at all like an actual indication.
--Dave
On Nov 25, 2012, at 15:56, Deems Davis <deemsdavis(at)cox.net (deemsdavis(at)cox.net)> wrote:
[quote]We just returned from a trip to Yosemite for Thanksgiving. On the return flight leaving Mariposa Airport, after pulling everything back to 25 Sq for climb, I had exited the pattern and established a climb (at) 105 kts when I noticed that the MP was reading 30 " !. My 1st reaction was that I must not have pulled the throttle back, but when I pulled the throttle back to 25" the fuel flow dropped to 10 gph, and the engine noise softened considerably. I increased the throttle back to where the fuel flow should have been for climb out and watched the MP slowly drop back to 'normal'. All other gauges appeared to be reading what I would expect them to be. I monitored everything closely for the next 30 mins and everything looked and acted 'normal'. About 1:30 into the flight everything was stable (at) 22" MP and 2350 RPM, and again the MP suddenly increased to 26". Again all other guages read normal, and no change in the sound of the engine. Once again the MP slowly decreased until it settled again (at) 22".
Does anybody have any similar experience or insight into what the root cause could be?
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Eric_Kallio
Joined: 29 Jan 2006
Posts: 149
Location: Baton Rouge, LA
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| Posted: Wed Nov 28, 2012 4:47 am Post subject: Re: Manifold Pressure 'excursions' Your feedback wanted |
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Not to hijack Deems' thread here, but along the lines of MP indicating issues... When I turn on my boost pump the MP indications go up by 4 PSI. No other changes in engine indications (CHT, EGT, RPM). Anyone witnessed anything like this one before and have any thoughts on where to begin tracking this one down?
Eric
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flying-nut(at)cfl.rr.com
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| Posted: Wed Nov 28, 2012 7:10 am Post subject: Manifold Pressure 'excursions' Your feedback wanted |
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Scratching my head over this one. There should be no connection between
MP and the boost pump ..... except maybe an electrical connection with
the MP sensor if you have one. I find most electrical gremlins can be
traced to poor grounds or ground loops. so check the ground for the
boost pump.
Linn
On 11/28/2012 7:47 AM, Eric_Kallio wrote:
| Quote: |
Not to hijack Deems' thread here, but along the lines of MP indicating issues... When I turn on my boost pump the MP indications go up by 4 PSI. No other changes in engine indications (CHT, EGT, RPM). Anyone witnessed anything like this one before and have any thoughts on where to begin tracking this one down?
Eric
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=389244#389244
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