GRT Avionics

I have an issue with my Manifold Pressure reading on my composite Long EZ......When the EIS and HXr power, and the engine is running, the reading is normal around 22.2 and its correspondent % Power reading. However, when I turn the alternator ON, the reading goes to 39, same RPM. Jeff commented that the electrical ground used by the MP and HXr was charging due to the high current of the alternator. He recommended changing the ground wire to a higher gauge and position too. I re-wired it to the engine mount where the all the common ground are, fired her up and still the same issue. Any other insight on how to correct this scenario?? Thanks in advance!!

Afif,

Is the manifold pressure reading the same on your EIS and your HXr?

Is your EIS located in the rear near your engine? Does the manifold pressure change on it when you turn on the alternator?

You say the reading is normal at 22.2. That seems pretty low to me. Is that on the ground (what is the elevation of your airport?)? And at idle? Or is that in flight? What rpm? What flight altitude? What manifold pressure is indicated with the engine not running?

To help you further, what is the Scale Factor and Offset for your manifold pressure sensor?

Let's see if we can figure out what is happening.

Jim Butcher

Thank You Jim for your effort to help figure out this gremlin. I will get back you soon with the inquiries. Yes the MP sensor is on the Back an it jumps from substantially when the Alternator is ON. It seems it is a ground problem, however, I changed the wire gauge and position and still have the same issue. I'm a sea level here (80ft), The AuxSF is 200 and Auxoff is 64. I haven't flown the aircraft yet after the upgrade and still detailing small details... However, hopefully soon....please private email me afif at saybeengineering dot com so i can send you a video of it..... Regards,

Wanted to post that my MAP issue has been resolved.I had been trying to use the connection of the MAP reading of my electronic ignition with a TEE to connect the GRT MAP Sensor. Nevertheless, instead of continue to troubleshoot this, I decided to disconnect one of the primer lines and installed a new line directly to the instrument and now the readings of MAP, % power are correct.....Thanks for everybody's input!!!!

Regards,