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Proper manifold pressure line


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The transition from large tubing to small copper tubing is just a reducer on mine. I ordered the snubber Art V recommended and it turns out to be the same thing JPI recommended.   I assume this allows the elimination of the copper tubing and use of a regular hose?

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On 4/22/2019 at 12:02 AM, Gary0747 said:

Jeev,

The sensor is installed on the firewall with the JPI supplied Adel clamp which is not nearly as solid and secure as the bracket mounts the others show.  We used the original copper tubing coil which we assume did some dampening.  We obviously did not use the small aluminum tubing with the weep hole that was on the cabin side of the firewall and no doubt did some additional dampening on the original gauge.   I can’t see how just a straight hose connection to the new transducer does any dampening unless there is an additional orifice in the hose?  Perhaps I am the only one even noticing this variation in the MP instantaneous measurement?   The variation does not seem to show up in the % HP readout due to apparent averaging in the JPI software.  

You’re not the only one.  My jpi 930 MAP fluctuates about.5” too.  I’ve grown use to it.  My FF fluctuates a bit as well.  %HP and other readings are stable.

 I did contact jpi support and they want me to send in the unit for updated software to fix these issues.  If that doesn’t work, they move on to the snubber solutions.  I just haven’t had a good time to pull mine and send it back.

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You’re not the only one.  My jpi 930 MAP fluctuates about.5” too.  I’ve grown use to it.  My FF fluctuates a bit as well.  %HP and other readings are stable.
 I did contact jpi support and they want me to send in the unit for updated software to fix these issues.  If that doesn’t work, they move on to the snubber solutions.  I just haven’t had a good time to pull mine and send it back.


I REALLY wish they would allow field installable firmware updates. Pulling the unit to have it updated is a BIG deal since we are talking about primary instruments. My plane was down 3 weeks the last time it was sent in. Pulling a Garmin radio is not typically a grounding situation.

I get keeping the mechanical repairs in-house, but firmware patches should be field installable.

BTW - the firmware update fixed my manifold fluctuations.


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My EDM 900 was purchased in January but was wondering if you have a firmware version more recent than this?


The manifold pressure firmware fix was added a least a year maybe two ago. If you are seeing it with a unit built in January, you’ll need to add the snubber.


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  • 2 years later...
On 4/25/2019 at 6:17 AM, Marauder said:

 


The manifold pressure firmware fix was added a least a year maybe two ago. If you are seeing it with a unit built in January, you’ll need to add the snubber.


Sent from my iPad using Tapatalk Pro

 

Do you have pictures of your snubber?  I’m gonna try one on the MP and if that works, maybe the oil pressure.  I bought the recommended snubber but it’s an npt thread connection and the lines use a flare type… by the time I add an adapter to each side of it, I’ve got a 4 inch piece of steel to add to each line. Doesn’t seem right.

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26 minutes ago, Ragsf15e said:

Do you have pictures of your snubber?  I’m gonna try one on the MP and if that works, maybe the oil pressure.  I bought the recommended snubber but it’s an npt thread connection and the lines use a flare type… by the time I add an adapter to each side of it, I’ve got a 4 inch piece of steel to add to each line. Doesn’t seem right.

I don't think I have a picture on my PC but I'll look. If I don't have it, I will see if I can snap a picture when I go over to the airport next time.

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1 minute ago, Marauder said:

I don't think I have a picture on my PC but I'll look. If I don't have it, I will see if I can snap a picture when I go over to the airport next time.

Thanks.  I’m learning more than I ever wanted to know about different types of pipe threads, but it appears snubbers use NPT and the sensor and lines are unjf / tapered jic.  These two aren’t compatible without an adapter.  I end up with an adapter on both ends of the snubber.  Maybe that’s ok?

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This is the snubber I put in my MP line. My 900 was well after they supposedly fixed it with a firmware update but I was having constant fluctuations. With this snubber it is rock solid.

https://www.mcmaster.com/3820K36/

I wrote an article in The Mooney Flyer last October about upgrading from the 830 to the 900 and listed the adapter/couplings that I used for the lines to the sensors.

https://themooneyflyer.com/issues/2020-OctTMF.pdf

"It is also possible that you can use the lines that ran to the firewall for your oil, fuel, and manifold pressure, although they will likely not fit the sensors that come with the 900. The lines will not fit the fittings that come with the sensors. However, instead of using the ones that come with them, you can use a combination of a coupling and fitting. The manifold and fuel pressure lines on my plane are a -2 size, so an AN910-1D coupling along with an AN816- 2D fitting did the trick. The fitting has pipe threads on one end flared on the other. The oil pressure line is a larger -3 hose and it needed an AN816-3D fitting.

Here you can see the black fitting that comes with the sensor from JPI, as well as the coupling and fitting above it, which will fit the smaller hose to the sensor."

image.png.1b1eab31c4b1fd77ac0b02f4a9e622c2.png

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16 minutes ago, Skates97 said:

This is the snubber I put in my MP line. My 900 was well after they supposedly fixed it with a firmware update but I was having constant fluctuations. With this snubber it is rock solid.

https://www.mcmaster.com/3820K36/

I wrote an article in The Mooney Flyer last October about upgrading from the 830 to the 900 and listed the adapter/couplings that I used for the lines to the sensors.

https://themooneyflyer.com/issues/2020-OctTMF.pdf

"It is also possible that you can use the lines that ran to the firewall for your oil, fuel, and manifold pressure, although they will likely not fit the sensors that come with the 900. The lines will not fit the fittings that come with the sensors. However, instead of using the ones that come with them, you can use a combination of a coupling and fitting. The manifold and fuel pressure lines on my plane are a -2 size, so an AN910-1D coupling along with an AN816- 2D fitting did the trick. The fitting has pipe threads on one end flared on the other. The oil pressure line is a larger -3 hose and it needed an AN816-3D fitting.

Here you can see the black fitting that comes with the sensor from JPI, as well as the coupling and fitting above it, which will fit the smaller hose to the sensor."

image.png.1b1eab31c4b1fd77ac0b02f4a9e622c2.png

Thanks Skates.  So it seems that you have a sensor, coupling, snubber, fitting, then MP line?  Do you have a picture of it assembled?  
 

Thanks very much for the help!

rags

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9 minutes ago, Ragsf15e said:

Thanks Skates.  So it seems that you have a sensor, coupling, snubber, fitting, then MP line?  Do you have a picture of it assembled?  
 

Thanks very much for the help!

rags

I can take a picture tomorrow evening when I'm out at the airport. For what it is worth, this is what my MP looked like before in cruise, fluctuations of about 0.5 a few times every minute, like clockwork.

image.thumb.png.2954e50425d55f21b3c9ddc5b2f6689e.png

After the snubber this is what it looks like.

image.thumb.png.51bdfb13496385e2100dacd034a3b435.png

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28 minutes ago, Skates97 said:

I can take a picture tomorrow evening when I'm out at the airport. For what it is worth, this is what my MP looked like before in cruise, fluctuations of about 0.5 a few times every minute, like clockwork.

image.thumb.png.2954e50425d55f21b3c9ddc5b2f6689e.png

After the snubber this is what it looks like.

image.thumb.png.51bdfb13496385e2100dacd034a3b435.png

Yep, the above is exactly what mine looks like.  Hoping this fixes it !

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You can make your own snubber very easily.  Press the shank of an appropriate rivet into the AN816 pipe nipple, then drill a number 60 or finer hole thru the centre of the rivet.

17DD6184-FB8D-42AE-AA46-C2AC2B032F94.jpeg

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Richard,

Fantastic details…

Technical solution with graphic proof of it working…

Are you an engineer in that business office? :)
 

One question…

There were three orifice sizes listed in the McMaster catalog page…

Which one did you use for your MP sensor?

Sort of like knowing what size hole to drill in Clarence’s solution…

Best regards,

-a-

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19 hours ago, M20Doc said:

You can make your own snubber very easily.  Press the shank of an appropriate rivet into the AN816 pipe nipple, then drill a number 60 or finer hole thru the centre of the rivet.

17DD6184-FB8D-42AE-AA46-C2AC2B032F94.jpeg

This has been referenced a few times, I would really love more information on how to build this.

Slightly more research produces an answer:  https://www.kitplanes.com/no-restrictions/

 

Edited by cctsurf
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12 hours ago, carusoam said:

Richard,

Fantastic details…

Technical solution with graphic proof of it working…

Are you an engineer in that business office? :)
 

One question…

There were three orifice sizes listed in the McMaster catalog page…

Which one did you use for your MP sensor?

Sort of like knowing what size hole to drill in Clarence’s solution…

Best regards,

-a-

Ah, didn't realize the link didn't also pull up the orifice size. I took a guess and went with the 0.015" diameter. If that didn't smooth it out I was going to go down a size but wanted to start with the biggest and work my way down. Pictures coming later today.

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10 hours ago, cctsurf said:

For those interested in the weep hole size and other information related, Mooney SBM20-103 (https://www.mooney.com/wp-content/uploads/2020/12/SBM20-103.pdf) references a .023 dia hole and also has a lot more information on the proper manifold pressure line.

If you have the original ships gauges in there this would be applicable, but I'm not sure that applies with the installation of the sensor for the EDM-900. 

On 6/29/2021 at 11:31 AM, Ragsf15e said:

Thanks Skates.  So it seems that you have a sensor, coupling, snubber, fitting, then MP line?  Do you have a picture of it assembled?  
 

Thanks very much for the help!

rags

The snubber is the opposite end of the line from the sensor. It is in the head, then the fitting which normally screws into the head, and then the line. 

20210630_182205.thumb.jpg.9d9e9a5ac09df07054abe4a4271d96f0.jpg

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Way to go CC!

The reference for the weep hole is a hard one to put a finger on…

 

For Richard…

The weep hole is designed to match the needs of the mechanical MP gauge…

So… the electronic MP sensor doesn’t need or want a weep hole to be added to the line…

The purpose of the weep hole is keep fuel vapors from getting into the mechanical MP instrument…

The 1/8” aluminum line would fill with the blue goo over time… up to the weep hole…

Something that occurs every shut-down, over decades of time…

PP thoughts only, not a mechanic…

Go MS!

Best regards,

-a-

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So, Now my dilemma...  I have installed an edm-900, but I have also retained my original manifold pressure gauge.  The manifold pressure on the edm is jumping around and would apparently appreciate a snubber, but I also feel like I should have provided a weep hole for the mechanical gauge...

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Just now, cctsurf said:

So, Now my dilemma...  I have installed an edm-900, but I have also retained my original manifold pressure gauge.  The manifold pressure on the edm is jumping around and would apparently appreciate a snubber, but I also feel like I should have provided a weep hole for the mechanical gauge...

Why did you keep the original gauge? The 900 is certified primary. 

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Hmmmm…

Need to visit a different cylinder to connect the MP sensor for the JPI….

Or… look at this way… Your primary MP gauge legally has a specific location to detect the MP from…

The other cylinders will have the same MP, connect the other gauge as a back-up there…

Consult your mechanic for the details… 

Definitely won’t be able to mix and match the JPI with a gauge that needs the weep hole…. 
 

The weep hole changes the actual pressure in the line… just our MP gauges know this already and have their calibration to match…

Without the weep hole… our MP gauges go off scale while idling…

When the weep hole is too large… our MP gauge error slides towards being a barometer depending on the size of the hole…

 

PP thoughts from my M20C experience…

Best regards,

-a-

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19 minutes ago, Skates97 said:

Why did you keep the original gauge? The 900 is certified primary. 

Having had both tach and map gauges fail on me before, and alternator issues as well, I like having a backup...  I don't need all the other gauges to fly and especially land, but when I didn't have a working tach or map gauge I was pretty uncomfortable.

10 minutes ago, carusoam said:

Need to visit a different cylinder to connect the MP sensor for the JPI….

Or… look at this way… Your primary MP gauge legally has a specific location to detect the MP from…

The other cylinders will have the same MP, connect the other gauge as a back-up there…

Consult your mechanic for the details… 

I honestly hadn't thought of splitting them and using a different cylinder for the original map gauge...  Duh.  Used a different one for the SureFly ignition I installed at the same time.  I feel like I'm running out of cylinders to tap for MAP, I'll only have one cylinder left...  ;)  I don't have any plans for that one...yet. ^_^

Edited by cctsurf
alternator
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