MP Fluctuation issue on Dynon

Any suggestions on how to stop the MP display on my Dynon EMS from fluctuating??

The manual said put a restrictor in it. It already has one coming off the engine, so I made one out of solid aluminum tubing that was ~3/4" long and drilled it out with a #60 drill.

It's better but now it is fluctuating about 0.6" instead of more than 1".

Let me guess, put another smaller restrictor in it. If so, I can use the 0.028 restrictor that I just took out of the fuel injection system and put it in the line. At least I know where I can find it later if I need it.

Filter

Webb

I went through all this tried different restrictors and finally what worked was a cigarette filter in the line. One of my mates looked oddly at me when I asked him for a cig but laughed when I just took the filter.

Place it in the line in front of the sensor.

Another advantage you'll not get any junk going into the sensor.

Peter

As Pete says, the answer really is a "smaller" restrictor, or more volume after the restrictor.

Things like compressed foam work well also. You should basically not be able to blow through it.

I used one of Van's restrictor fittings on the cylinder. I also used Van's MP penetration kit (my MP transducer is mounted after of the firewall). The MP is rock solid.

I have flown a friend's RV that used a cigarette as a filter and although the MP was very steady it also lagged quite a bit more than mine does. Not that it really matters because you don't need MP to be that responsive (unless of course you have some sort of EI or FADEC that requires it) and you're picking up MP off the same port.

I put an .030 restrictor in my line and it stopped the fluctuations.

I'd put in the .028 one you have. A lot easier then drilling those tiny holes!

Ted

Cigarette butt fixed it. I happen to have a spare 0.028 restrictor which I'm going to switch to later on so it will be a bit faster but for now, my plane would "rather fight than switch".

kiwipete said:

Webb

I went through all this tried different restrictors and finally what worked was a cigarette filter in the line. One of my mates looked oddly at me when I asked him for a cig but laughed when I just took the filter.

Place it in the line in front of the sensor.

Another advantage you'll not get any junk going into the sensor.

Peter

Click to expand...

Now rock solid

Results I have tried and what worked.

- Cigarette filter rock solid
- 0.028 restrictor fluctuated by 0.2"
- 3/4" piece of solid aluminum tubing drilled with a #60 drill fluctuated 0.6"
- Combo of the 0.028 restrictor and the #60 drilled tubing rock solid and was a bit faster on the response (I left that one in place since it was the last thing I tried)

Conclusion - Use of a cigarette filter is an inexpensive fix that works and is one of the easiest fixes for this problem of all.