Dynon EMS MP Sensor

I have come across a repetitive and unusual situation with my EMS. The system has gone competely bizerk (technical term) a few times. Erroneous indications all across the board to blanking out. Extensive trouble shooting/consult with Dynon etc etc.

After a few bouts with this, it finally hit me that each one was preceeded by the MP sensor acting up first. Then things progressively going down hill from there. The last two bouts I've just replaced the sensor and presto everything is full up again. I am on my 3rd or 4th MP sensor in 210 hours and 1 1/2 years. About $60.00 from Summit racing. The MP reading always seems to be fluctuating slightly but is useable.

Running the large HD EFIS and EMS screens, really like 'em but wondered if anyone else out there has experienced anything similar or if I'm in my own self inflicted purgatory?

Steve Barbour
N322SF

To stop the MP fluctuating you need to put a restrictor in the line. I tried various sizes which helpped but still gave a little flucation. Then someone on the dynon forum suggested a cigarette filter in the line and now the MP is rock steady.
As for the other faults I haven't experienced anything with my DEK180

Peter

Peter, when you say rock solid, do you mean that if you don't change the power setting the MP stays put or does it read up and a small amount. If I run 20 inches MP, mine will fluctuate from maybe 19.5 to 20.5 and never settles down. Perhaps a filter will fix mine.
Ron

Ron,

Check out this tread.

Rock Solid

By rock solid I mean that it reads the MP without fluctuating. Of course when you change the throttle position you see the MP changing straight away and you can accurately set the new power setting.
Say if you have 23.5 set, before when I had just a restricter, it would read between 23.2-23.7 now with the filter it just reads 23.5.
I got the idea from the Dynon forum. If you get a cigarette and take out the filter it is a nice firm fit in the line. This then damps out the fluctuations. You can still suck or blow through the line slowly.
There's no harm in trying it. If you smoke it'll cost you one cigarette. In my case a mate looked really shocked when I asked him for a cigarette and laughed when I said actually I only want the filter.

Peter

My MP solution

I was going to use Vans MP gauge and the related parts but changed course and have come up with a system that will use only some of the Vans parts. I started by modifying this AN fitting (pictured below) by partially drilling it out to a larger inside diameter and inserting a short soft aluminum rod into it and seating the rod on a shoulder formed inside the fitting. That was done in order for the small rod not to be sucked back up into the engine. After inserting the rod I then smashed it, a bit like smashing a rivet, to swell it up in the drilled hole hopefully locking it into place. I then drilled a very small hole through it.




I used Vans provided hose to run from that fitting to the firewall and used a bulkhead fitting left over from making my fuel tank vents instead of using the standard Vans part that hooks up to very small diameter plastic tubing. What I will have now is a split 1/4” MP line with one side going to my LASAR controller and the other side to my EMS's transducer. After reading posts in this thread I believe I will fix up a small cartridge that I can load a cigarette filter into. I can probably buy a single cigarette at the coffee shop.

Rivethead said:

After reading posts in this thread I believe I will fix up a small cartridge that I can load a cigarette filter into. I can probably buy a single cigarette at the coffee shop.

Click to expand...

No need, that single restrictor you put in should do the trick.

BTW, I simply drilled an AN470AD4 rivet and put it in the bulkhead fitting where the MP line passed through the firewall. That solved the problem for me and no cigarette filter material moving round in my MP line.

Steve,
On a different topic, I'm more worried about why your sensors are dying so often. These are GM parts, used on cars for hundreds of thousands of miles with very few failures, and we also see basically zero failures on them.

What is the source of the voltage you are using to run the sensor, and where is it physically mounted in the plane?

Funky MP Sensor

The MP sensor is located cockpit side of the firewall. I have unhooked the electrical plug from the sensor. The EMS resumed normal function. I then mounted a steam gauge MP indicator under the panel and ran the existing MP line to it. When I unhooked the line there was a touch of oily residue in low point of the line just a few inches from the entry point of the sensor. The sensor may be getting compromised by this oily residue?

Plan is to fly a few hours on the steam gauge MP and if the unit performs normaly, which I suspect, I will just re-fabricate all associated lines on the sensor/wiring harness and install a catch loop in the MP line and try it again. Trying to confrim I am chasing the right gremlin.

Thanks

Steve B.

Have since flown a few sorties with the alternate MP guage and all is normal. I will now install new MP lines with a cig. filter in it and a catch loop and hook that to a new MP sensor and let you kow what happens.

Steve B.

Most conventional MP gauges will have a lot of damping built in.
Hope the cig filter works ok.

Peter