JPI EDM 900 Tach Settings

[BrianW]

Hi All,

I was looking for definitive info and couldn't find it easily, so I researched it and made a call to Mooney International Technical Support.

The JPI EDM 900 has its tach adjustment factory default to be 2400 rpm.  But I wasn't sure what Mooney set our average cruise engine speed to be on our tachs for our tach time.

I called Mooney International Technical Support regarding my M20J.  They looked up my original mechanical tach and told me it was setup for tach time to equal run time at 2500rpm.

Its a good idea to change both the tach time and tach adjustment before the JPI EDM900 runs past its first 10 hours.  After 10 hours the tach settings lock and cannot also be changed.  This is to prevent tampering.

After it is used more than 10 hours (or if you buy someone else's used JPI), you must send it back to JPI to have the tach settings modified.

I'd set the tach time to your TTAF, which makes for easy logbook entries.

It's important to set your tach adjustment to match what Mooney specified.  Otherwise if you don't, and it remains at 2400rpm, when you cruise at 2500rpm your tach will be adding time faster than clock time accidentally "aging" your plane adding hours at a faster rate than it was supposed to.

Edited June 7, 2019 by BrianW

[StevenL757]

What does your POH say?  JPI will set the tach and other values on your config worksheet to whatever is stated in your POH/AFM...Mooney shouldn’t need to verify anything unless there’s a discrepancy in the POH.

Also not clear what you mean by the tach time needing to be set before the EDM hits 10 hours.  When JPI configures a unit, they set that value at their location before shipping it to you or your installer.  The only reason it would need to be changed is if you have, say, an engine modification that warrants it (a 280hp to 310hp as on the Ovation, for example, which warrants an RPM change from 2500 to 2700), or another problem(s) requiring the unit to be reprogrammed.

Unless JPI have changed something in their core code or their key programming process recently, they can change any or all of their factory settings anytime...the only obvious issue is having to send the unit back to CA.

[BrianW]

The POH doesn't specify the value where the tach time runs at the same speed as real time. 

According to Mooney Technical Support, over the years numerous tach manufacturers/supliers were used.  Some tachs were mechanical, and some were electronic.  But Tech Support can look up the specs for the original tach installed in your plane by the tach's part number and your plane's serial number.

Given the wide variety of tachs, and the POH not having the spec where tach equals real time, it seems prudent to have a default valve but allow the installer or pilot to fine tune settings.  And 10 hours until it locks the installer/user out from making changes later is probably an FAA requirement to prevent time tampering.  So after 10 hours one has to send it back to JPI to modify.

JPI has a lot more settings than just those covering the basis specs given in the POH, like MAP calibration, date, time, gps type, etc.  And those should be fine tuned and set during install or shortly thereafter.

I'm not sure how it looks when JPI locks out certain features after 10 hours. It may allow you to still get to the variable but not allow any changes to be saved.  Or it may hide the setting entirely in it's menu system. I'm not sure.

If it allow you to see the rpm adjustment but not save any changes that may explain why someone's tach may be running faster on the JPI over the stock mechanical tach, cuz the mech tach may run true at 2500 while the JPI may not allow a change from it's default of 2400rpm, if it been installed for over over 10 hours.

I would call Mooney Tech Support to get  your true rpm (don't just enter random numbers hoping to see some effect).  Get you real number and only use that number!

After I had my true rpm number for my plane, I'd definitely call JPI to figure out why there's a discrepancy.

Edited June 8, 2019 by BrianW

[jetdriven]

I got the same letter, it said 2556 rpm. Mechanical techs come in certain rpm settings. 2300 and 2566 come to mind. I had a mechanical tach that was installed  for 20 years that was the 2300 rpm version.  Counting 1.2 hours per clock hour since then.  Changed the tach and adjusted the time 

[hypertech]

JPI sets a bunch of limits you can’t change and this isn’t one of them. They didn’t set it and neither did the avionics shop or mine. Luckily I noticed when I landed from my flight home and my tach time didn’t make any sense. I was at 8.9 out of the 10 hours. 

 

Before the 10 hours, you can set the tach time and true rate for whatever you want. I haven’t tried to change it since then but do understand that it should now be locked and require a trip to jpi if you need to change anything. 

[RLCarter]

Question....... Why wouldn't you set it for 1 hour is 1 hour? 

[Jim Peace]

16 hours ago, RLCarter said:

Question....... Why wouldn't you set it for 1 hour is 1 hour? 

That would be fine with me except that some normal cruise settings will give you more than 1 hour engine time logged in a 1 hour period.  Why put that extra time logged on the engine if you don't have to?  As shown below my time gets logged on a JPI 900 one for one at 2400 rpm....I make sure I cruise around 2400 or below.