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JPI EDM830 Manifold Pressure 1-2 inches higher than Steam gauge

bill98

By bill98
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bill98 Community Regular

bill98

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I noticed the other day my JPI shows MP an inch to 2 inches higher than the “primary” steam gauge I have for manifold pressure. 

 

When I started going off the steam gauge for MP my speed increased big time. 

 

Anyone had had this issue before? I am hoping this is just a simple calibration adjustment needed. 

DVA Rising Star

DVA

Posted
Posted

The JPI 830 has a offset adjustment to set the resting MP to the corrected sea level reading. Page 46/47 of the JPI Manual explains this.

You can spot check which instrument (ship gauge or JPI) is off by taking the current ATIS altimeter reading and subtracting for the field elevation. Each 1000 feet above sea level equals 1” of pressure. So if your field is at 1000’ asl and the current atis is 30.05, your engine off MP should be 29” (29.05 to exact but that’s not necessary). The relationship for pressure is linear so if your field elevation is 300’ asl, then subtract .3”, etc.


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bill98 Community Regular

bill98

Posted
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1 hour ago, DVA said:

The JPI 830 has a offset adjustment to set the resting MP to the corrected sea level reading. Page 46/47 of the JPI Manual explains this.

You can spot check which instrument (ship gauge or JPI) is off by taking the current ATIS altimeter reading and subtracting for the field elevation. Each 1000 feet above sea level equals 1” of pressure. So if your field is at 1000’ asl and the current atis is 30.05, your engine off MP should be 29” (29.05 to exact but that’s not necessary). The relationship for pressure is linear so if your field elevation is 300’ asl, then subtract .3”, etc. 


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I was coming here to say I found the information!

I am hoping the difference has not affected my engine break in! 

 

Also have good news.... I finally managed to get the EDM830 to send data to me USB stick! I did notice it is still on Firmware Version 3.16 though. The latest version is 3.53

carusoam Grand Master

carusoam

Posted
Posted

Fortunately, engine break-in is most often a WOT affair... no matter what the MP gauges say...  :)

Fortunately2, the JPI 830 is not a primary engine instrument... so, no matter what it says, the primary ship’s gauge should be telling the truth...

Check all instruments for MP and rpm at engine OH... a good calibration if they are off...

PP thoughts only, not a mechanic...

Best regards,

-a-

  • 1 year later...
Andviation Newbie

Andviation

Posted
Posted

Hi, I just got my first Jpi 830 installed. Every reding is good but cannot get a MAP press reading with the engine off. Instead it shows a red X on the scale. Is this normal or should the e gine be running for MAP to show? 
 

my logic tells me it should be displayed regarding of engine state. 
 

thank for any clarification!

carusoam Grand Master

carusoam

Posted
Posted

Welcome aboard And...

That can’t be right...

At wide open throttle... it is essentially a close reading to when the engine is off...

Depending on what filter you have and where your sensor is actually located...

A red X means something else is missing, and now you want to find out how to use your JPI...

It is important to get a reading before the engine is started to check your altitude setting... or it used to be normal to do this... back in the day... 

It should give a barometer type reading...
 

We don’t have a JPI guy around here, but we know a guy that sells the JPI equipment... he can get answers too...   @Jeev And he knows many of the usual answers to the usual questions...

Best regards,

-a-

ArtVandelay Grand Master

ArtVandelay

Posted
Posted
Hi, I just got my first Jpi 830 installed. Every reding is good but cannot get a MAP press reading with the engine off. Instead it shows a red X on the scale. Is this normal or should the e gine be running for MAP to show? 
 
my logic tells me it should be displayed regarding of engine state. 
 
thank for any clarification!

Definitely something is wrong it should read the barometric pressure when the engine is off.
Jeev Experienced

Jeev

Posted
Posted
On 2/26/2019 at 10:40 AM, bill98 said:

I noticed the other day my JPI shows MP an inch to 2 inches higher than the “primary” steam gauge I have for manifold pressure. 

 

When I started going off the steam gauge for MP my speed increased big time. 

 

Anyone had had this issue before? I am hoping this is just a simple calibration adjustment needed. 

Hi -  there is a simple calibration in the pilots guide.  It will take a few flight to get it right but it is east.  Take a look its listed in the manifold pressure section.

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