MAP Fluctuating

[WestCoastOz]

Yesterday I flew my Flight Design CTsw (Rotax 912ULS) for the first time since having done the lastest firmware update for the D120 & D100 and now find that the manifold pressure is fluctuating in flight up to approximately 200 Mb (5.9 inches of Merc).
All other engine parameters remain normal (RPM, FF, FP, OP etc) and there is no obvious engine surging occuring. Also the performance parameters are normal...i.e. IAS & TAS remain constant, so I strongly suspect an indication problem.
I have no reason to believe that the above problem is anything to do with the latest firmware update, however so as to remove to from the troubleshooting process, can anybody advise if they have experienced a similar problem?

Thanks

Dave

 

[dynonsupport]

Dave,
We've seen this before. The fluctuation is actually there in the engine, and we're just reporting it. This usually comes when the MAP pickup is close to a valve and the pressure there changes as the valves open and close.

The best fix for this that we have seen is a restrictor in the line to the MAP which averages out the pressure. Since you bought this LSA with the EMS installed, you should probably talk to Flight Design and see what they can do to help you install something to fix the problem. This is really an install issue, not a software issue.

We haven't heard of any problems with the new software on the EMS, so I doubt it's the problem, but restoring a backup on the EMS and taking a flight would prove that pretty quickly.

 

[WestCoastOz]

OK thanks....will try going back to the previous firmware version and see what happens.
During the first 25 hours of operation using the previous firmware version, the MP was absolutely stable at all times.

Dave

 

[dynonsupport]

Any chance that the factory installed a damper that has somehow come loose or something?

Just something to check if the firmware backdate doesn't fix it.

 

[Thomas_Schaad]

I had the same issue with my Pulsar XP, driven by a Rotax 912. I did now (as one of our collegues suggested here in the forum) put a cigarette filter in the MAP tube, just in between the sensor and the pick up. It works great and I have now an absolutely stable MAP annunciation.

I have to say, it was the fist time I was lucky about smokers, as one of them gave me the filter   Try it, it will probably help you as well.

Kind regards

Thomas

 

[WestCoastOz]

OK thanks Thomas....I will try that if going back to the previous firmware version does not solve the problem....I am not really sure why the MAP was perfectly stable up until now but will sort it out eventually.

Regards

Dave

 

[WestCoastOz]

I reverted back to the previous version of the firmware and the problem remains, so it is not a Dynon problem.....will now try restricting the MAP line between the pickup and sensor.

BTW everybody, whenever your Dynon Support program asks if you want to create a back up of anything....DO IT!!  When going back to the previous D120 firmware version, I didn't bother backing up the current version however as I soon found out......the HOBBS & TACHO times are now all wrong  :-[   and show about 4 hours less than actual.....oh well you live and learn by your mistakes.  :-/

Regards

Dave

 

[dynonsupport]

Note that in th EMS global setup menu, you can set the Hobbs and Tach times to any number you desire.

 

[dynonsupport]

Restoring a backup of the EMS will always reset the hobbs and tach timers to the value at time of backup, so it's always a good idea to write them down and then re-set them after the backup restore.

This does not happen during firmware updates, only backup restores.

 

[WestCoastOz]

Phew!.....thanks for that....I will enter SETUP and reset the times as I keep a written log and have all that data.

Dynon just keep on getting better!


Regards,

Dave

 

[yak55]

I had the same fluctuating issue but in my case I have a IO-360 not Rotax. I fixed the issue by going to the local Sears Hardware "aviation" dept and purchased a Briggs and Stratton fuel filter ($1.39). The filter has 1/4" ends. It is about the size of a quarter. The filter has a metal mesh inside as the filter. I stuffed small pieces of foam inside the filter on the what I called the exit side of the metal filter. I then connect the filter between the MP sensor and cylinder MP port. My MP is rock steady now.

Hope this helps!

 

[jlhrstv]

Re: MAP Fluctuating - Rotax & FLight Design fi

Hi all,

Recently Flight Design sent instructions for dampening the manifold pressure needle.  This may also be helpfull for other Rotax/EMS instillations.

The restrictor is availiable from Lockwood Supply 863-655-5100

Instructions attached.

John