I have uploaded the new Firmware for the EMS and this has helped to reduce some of the fluctuations from the MAP sensor. I have also installed a conventional gauge and this reads rock steady. Any ideas please on how to steady the readings on the EMS further, which can still vary wildly by several inches at certain throttle settings (whilst the conventional instrument remains steady). Thanks, Nic
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MAP Fluctuations
- Thread starter skyhi
- Start date
meljordan
Active Member
Hi Nick,
You didn't say what engine you are running, but I assume it is a Lycoming and that you are taking the manifold pressure from the intake port on #3 cylinder, which is the usual setup. I had this same issue with mine. The problem is that taking the manifold pressure right next to an intake valve that is opening and closing 1300 times per minute makes for some wild pressure changes at that location. On the mechanical pressure gauge, this is all buffered by the chamber and mechanism of the gauge, but when using a solid state sensor that can react to pressure changes in real time, each time the Dynon reads the gauge it is getting a different pressure depending on the position of the intake valve at that moment.
Anyway, I fixed mine by simply installing a small "buffer" in the MP line between the cylinder and the sensor. I went to the aviation department of ACE hardware and bought two 1/4" barb to 1/2" pipe male nylon fittings and an 1/2" pipe to 1/2" pipe female coupler. I stuffed foam rubber (be sure to test the foam and find some that fuel won't effect) into the coupler and screwed on the two barb fittings and now my MP reading is rock solid. I checked it against two other RVs with the same engine and intakes in formation at wide open throttle, and we were all reading the same MP within a half inch. Stuff the foam in there tight so there is a "restriction" when you try to blow through it. By the way, I don't see any delay in my system, when I change the trottle setting the MP moves immediately.
Another solution is to put a restrictor fitting in the Lycoming head where you take the MP reading. I initially tried this, but still had some dithering of the 0.1 inch readings. Perhaps the hole I had in the restrictor was too big?
Anyway, I hope this helps.
Regards,
Mel Jordan
RV-6A Tucson
You didn't say what engine you are running, but I assume it is a Lycoming and that you are taking the manifold pressure from the intake port on #3 cylinder, which is the usual setup. I had this same issue with mine. The problem is that taking the manifold pressure right next to an intake valve that is opening and closing 1300 times per minute makes for some wild pressure changes at that location. On the mechanical pressure gauge, this is all buffered by the chamber and mechanism of the gauge, but when using a solid state sensor that can react to pressure changes in real time, each time the Dynon reads the gauge it is getting a different pressure depending on the position of the intake valve at that moment.
Anyway, I fixed mine by simply installing a small "buffer" in the MP line between the cylinder and the sensor. I went to the aviation department of ACE hardware and bought two 1/4" barb to 1/2" pipe male nylon fittings and an 1/2" pipe to 1/2" pipe female coupler. I stuffed foam rubber (be sure to test the foam and find some that fuel won't effect) into the coupler and screwed on the two barb fittings and now my MP reading is rock solid. I checked it against two other RVs with the same engine and intakes in formation at wide open throttle, and we were all reading the same MP within a half inch. Stuff the foam in there tight so there is a "restriction" when you try to blow through it. By the way, I don't see any delay in my system, when I change the trottle setting the MP moves immediately.
Another solution is to put a restrictor fitting in the Lycoming head where you take the MP reading. I initially tried this, but still had some dithering of the 0.1 inch readings. Perhaps the hole I had in the restrictor was too big?
Anyway, I hope this helps.
Regards,
Mel Jordan
RV-6A Tucson
Mel, Many thanks for your explanation - I am running an XP360 and it makes perfect sense to smooth out the pressure variations before they get to the sensor itself. I will get the parts sorted and installed next week and let you know how it goes.
It may be a reasonable idea for Dynon to include a small kit with the EMS for this purpose with notes in the installation manual for Lycoming users, I would be happy to pay for the parts to save the initial concerns on wiring and pneumatic installation.
The link to Pelican's Perch (Manifold Pressure Sucks) - was really useful. Thanks
Rgds, Nic
It may be a reasonable idea for Dynon to include a small kit with the EMS for this purpose with notes in the installation manual for Lycoming users, I would be happy to pay for the parts to save the initial concerns on wiring and pneumatic installation.
The link to Pelican's Perch (Manifold Pressure Sucks) - was really useful. Thanks
Rgds, Nic