JPI MP display.

[Lood]

My brand new JPI EDM 900 is absolutely amazing, but it does take a bit of getting used to, I must add. It's almost like doing a conversion to type - it takes a while for your brain to put your eyes on the exact spot, immediately, to find what you're looking for.

Anyhow, among a few others, I decided to keep my old OEM MP/FF gauge and here's something that I've noticed. My OEM MP gauge is spot on when compared to the EDM 900's digital MP display and the OEM gauge is dead steady. If the MP is set, the needle will not move one mm. The MP on the EDM 900 however, is not. In flight, it continuously vary with about 1/2". Let's say I'm setting a MP of 21", the EDM 900 will continuously "hunt" between 20.8" - 21.3" odd. It is never stable or set on a single readout.

 

Is this normal with other owners who also have JPI's with the digital MP readout or might htere be an installation issue with mine? Probably not a big issue, but rather annoying.

[PTK]

This is the digital vs. analogue.

The digital has a much higher resolution than the analogue!

[N601RX]

My 830 didn't move around, and I haven't noticed it on the 900 that I just installed.  Do you know if the AN fitting on your engine is a open fitting or a special restricted one?.

[Marauder]

My 830 does not move once set either.

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[Lood]

My 830 didn't move around, and I haven't noticed it on the 900 that I just installed.  Do you know if the AN fitting on your engine is a open fitting or a special restricted one?.

 

I'm really not sure, but can probably find out from the guy who installed it. Would the particular fitting make any difference?

[N601RX]

Most factory gauges have a restricted fitting installed in them. Some are on the gauge end and some are on the engine end.  It looks like a regular AN fitting on the outside, but has a very small opening on the inside.  This kind of acts like a filter and prevents rapidly changing pressures. it also protects them from a potential pressure spike if a backfire occurs.   I know the 830 I had didn't fluctuate and I'm pretty sure the 900 isn't either.  I'll check next time I'm at the airport. You could try removing and plugging the line to see if the problem is Suction or Electrical.  You could also try turning it on while on the ground with the engine and everything else off and see if it is stable.

[Bob_Belville]

My 930 behaved as yours, a real distraction.

 

After sending JPI the data dump they provided a "snubber", a sort of check valve, dampener, that we installed in the line between the intake manifold and the transducer. I recall we did have to get an adapter to match connections types. Fixed the problem.

[PTK]

Now that I think about it my EDM800 doesn't fluctuate either. It's solid and in good agreement with the analogue gauge. 

[Marauder]

I just pulled up a video I made where I scanned back to the JPI 830 after 30 seconds. It was still on the same pressure setting.

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