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Manifold pressure reading in correctly (Read 294 times)
Apr 1st, 2018 at 2:56am

Charlrv9   Offline
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Why at 7500 feet today my RV 9 with  o- 320 lycoming
skyview manifold pressure reading 28 inch rpm reading 2400
I quite sure this is incorrect   I pull throttle back and a bit and then it come right 24/24 not sur what going wrong
Dynon can you help
Thanks
Charles Mifsud
 
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Reply #1 - Apr 1st, 2018 at 7:47pm

kellym   Offline
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You can check MP on the ground. With engine not running, it should within about 0.5" of the altimeter setting.
Once you start the engine, it should be under 12" at idle, preferably under 10".  If it is above 12-15" at idle, you have a leak in the system. Also, on take-off roll, if near sea level, it should be about 1" less than altimeter setting.
 
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Reply #2 - Apr 2nd, 2018 at 5:07pm

mmarien   Offline
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Murray M.
Saskatoon SK CAN

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The 28" at 7500' doesn't make sense though even if there was a leak. I fly WOT and checked a couple of flights at 7500 DA. I have a MAP of about 22.2 to 22.4. Using the rule one inch for every thousand feet: 29.92 - 7.5 = 22.4. So the best you should get at that altitude (not boosted) is 22.4 or so.

Are you using the 12V power from Skyview for the MAP sensor? or are you using another source? If the input voltage for the sensor isn't regulated it may give you different readings.
 

Glasair II FT - o320 - P-Mags - EFII - MTV 3 Blade CS - VP-X - Single 10" Skyview - Stratux Dual Band - zooooom ...
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Reply #3 - Apr 2nd, 2018 at 5:08pm

Dynon Avionics   Offline
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Dynon Technical Support

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The altimeter setting is the pressure that would indicate zero on the altimeter for your current atmosphere. So the MP only equals altimeter setting for sea levelish airports. Else you'd expect the observed MP to approx the altimeter setting minus 1" for every thousand feet of elevation.

Another way to test: Set your altimeter "baro" setting until altitude reads zero. In this case, your baro setting and your MAP should be close.
« Last Edit: Apr 2nd, 2018 at 5:09pm by Dynon Avionics »  

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