manifold pressure erratic

pilot1950

New Member
Joined
Jul 12, 2010
Messages
8
Turning on before chanking the reading on my EMS D120 jumps up and down and pegs alot. Where do I need to look. Also erratic after chank up. Can I disable the map reading till I can get it fixed? I have a rotax 912-ULS. Is it going to hurt anything (short out burn, fire, etc). THis started after an annual. Maybe they pinched a wire or something?? I think I have 4.2 firmware on my 2008 CTLS
 

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pilot1950

New Member
Joined
Jul 12, 2010
Messages
8
UPDATE... I found the sensor mounted on cabin side of firewall behind the D120. We wiggled all wires and connections to the D120 and no joy. The needle still jumped around like crazy. I went into the menus and turned off the view of the MAP display on the screen. Looks like a sensor problem I guess. I hear that I can find one at auto parts store. Do you have part no.? Sorry for the upside down picture.
 

Roger_Lee

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Joined
Aug 1, 2006
Messages
68
Hi 1950,

The map pressure on a CT will jump around because of the large MAP line and the pulsations through it. Take a Bing idle jet and insert it into the line where it comes off the cross over tube for the carbs where that line starts on the 912. The small orifice in the jet will reduce the pulsations and the readings will be very solid. Works like a charm.

You should really update the firmware to 5.4.3 on both Dynon's and the HS34 if you have that AP. It's easy to do.

p.s.
You ought to come over to the www.ctflier.com web site as many of these questions and more are answered. The site is a very friendly CT forum with lots of techs just for the CT. Call me if you have any questions 520-574-1080. I'm a CT service center.
 

pilot1950

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Joined
Jul 12, 2010
Messages
8
Thanks roger. I had a "steady" reading for 2 years and this behavior just appeared. I have a video of the D120 showing the needle jumping around with just the master turned on and the engine NOT running. I can email it if you want to see.

PS. I do get on the CT forum. Great site.
 

Roger_Lee

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Aug 1, 2006
Messages
68
Do the update. You may have a little software glitch that the update may remedy.
 

pilot1950

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Joined
Jul 12, 2010
Messages
8
OK about updating the firmware. I have a D100, a garmin 496 and CT flyer autopilot with my D120 all wired together. Does upgrading any of the firmware in any of these devices remove any of the settings. I have not upgraded in fear of screwing something up. (I do upgrade my GPS data.)
 
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