EDM 830

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Let'sgoflying!

Touchdown! Greaser!
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Feb 23, 2005
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Dave Taylor
Constantly showing ~3600rpm in cruise
Bonanza with IO-520 ie 2400rpm set on analog tach

A suggestion has been made this is a 4cyl vs 6cyl setting.
Reviewing the install manual it says that the cylinder number is something the computer figures out on its own, and sets during first startup... which seems to rule out that possibility.

The P-leads and grounds are solid.
Passes the live mag check.
 
You must have the correct RPM sensor for the mags. What kind of mags do you have?
 
I should have mentioned this is not a new install.
Been working fine for over a year.
No change in mag sensor.
 
While it does auto-calculate the number of cylinders based on the detected number of EGT/CHT probes, that's still a recommended check to ensure that it is properly set to 6 cylinder in the factory limits. Why it could have suddenly changed, who knows? Did you have any recent work done (avionics interfacing to a GPS or anything), or gone in to the programming mode to change any other parameters that might have accidentally changed things? I've seen a number of sensor failures over the years, but they've always just stopped reading anything. JPI uses magnetic pickup sensors, which are normally relatively immune to various sources of noise that might get picked up in other signal sources... they usually work until they just die completely. I would take a look at the mag, make sure the sensor is still securely attached, check the ground for the EDM (it should be grounded directly to the engine block somewhere, not to the airframe), I'd also try unplugging the sensor (there is a short pigtail on the sensor that has a mate-n-lock connector you can pull apart) and doing a quick run of the engine, it should read zero, if you are still reading something, the EDM has malfunctioned. JPI has some additional suggestions here: https://www.jpinstruments.com/FAQCategory/rpm-and-map/ under "RPM, wrong reading or erratic" ... but if the reading is matching that 50% higher across the range, that definitely sounds like the cylinder setting got changed somehow.
 
Thanks Ryan
Last night I did look at the sensor and p-leads - everything appears tight.
The sensor was installed at a 30degree angle - I need to re-check the manual, I think it says 0degrees and 90degrees, depending on the mag model.
 
The EDM if unpowered for a long time forgets its setting and will indeed power up with the wrong number of cylinders. It's happened to me twice.
 
flyingron said:
The EDM if unpowered for a long time forgets its setting and will indeed power up with the wrong number of cylinders. It's happened to me twice.
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Wow, that's disturbing. I would think they would store all that stuff in non volatile ram.
 
flyingron said:
It can go a long time unpowered, but it isn't truly non-volatile.
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Is there a battery in there somewhere? Dallas Semiconductor used to sell clock chips with batteries potted into them.
 
asicer said:
Is there a battery in there somewhere? Dallas Semiconductor used to sell clock chips with batteries potted into them.
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Back in the stone age maybe. In this day and age, flash memory is very cheap. I might believe it if this was a 730 but the 830 isn't that old.
 
Joe_B1 said:
Back in the stone age maybe. In this day and age, flash memory is very cheap. I might believe it if this was a 730 but the 830 isn't that old.
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Yeah, but how old is the 830? I thought it's been around a while...
 
Cheap flash has been around that long. Just look at SD cards for camcorders. Gigs for pennies now, 10 years ago it was Megs for pennies.
 
this was indeed a loss of programming, upon restart it defaulted to 4 cyls.
That's all I know about this.
 
My 830 lost all of its settings once and I had to do the configuration again. I now keep a copy of my configuration settings on a spreadsheet.
 
kshaw said:
My 830 lost all of its settings once and I had to do the configuration again. I now keep a copy of my configuration settings on a spreadsheet.
Click to expand...

Or just record the settings by using your smart phone as you step through them.
 
730/830 should write a settings.txt file with all the settings to the USB stick when you download flight data.
 
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