MGL Extreme EMS question

[Pilot135pd]

I'm starting to program a new MGL Extreme EMS system (version 2) and have this issue:

Normally I would see Manifold Pressure with the engine off the same as ambient. I adjusted the MAP calibration factor to the maximum (page 36) and with an ambient pressure of 30.06 the best I can get is 29.2.

Any ideas why or how to correct it?

 

[sprucemoose]

Just a guess but is 30.06 the local ambient pressure or the altimeter setting?

 

[Tommy123]

MGL has it's own owner's forum. Go to Michigan Avionics for the link.

 

[RV8JD]

I see Vaca Moo Airport is 590 ft above SL (estimated).

The traditional quick check of your MP gauge is to set field elevation, note the value in the Kollsman window, and subtract 1" Hg per 1000 feet above sea level. For example, if your field elevation is 200 feet set 200 feet on the altimeter, then subtract 0.2 from the Kollsman. In theory, if the Kollsman said 29.92, the MP gauge should read 29.72.

Like any rule-of-thumb, it's not super accurate, just close. The answer will be as much as 0.1" Hg too high below 6000 feet, and could be worse if your altimeter is out of calibration.

Here's a simple web calculator which will work on your phone, at the airport. Seems to be pretty accurate.

http://www.csgnetwork.com/stationpressurecalc.html

Input the altimeter setting from your best local source (AWOS, ATIS, etc.) and the altitude where your airplane is parked. Tap calculate, and compare "station pressure" to your MP gauge, engine off. The calibration risk is the accuracy of your local FAA equipment.

 

[Pilot135pd]

Just a guess but is 30.06 the local ambient pressure or the altimeter setting?

Darn, it's the little things that get you. Correct, thanks.

 

[Pilot135pd]

I see Vaca Moo Airport is 590 ft above SL (estimated).

The traditional quick check of your MP gauge is to set field elevation, note the value in the Kollsman window, and subtract 1" Hg per 1000 feet above sea level. For example, if your field elevation is 200 feet set 200 feet on the altimeter, then subtract 0.2 from the Kollsman. In theory, if the Kollsman said 29.92, the MP gauge should read 29.72.

Like any rule-of-thumb, it's not super accurate, just close. The answer will be as much as 0.1" Hg too high below 6000 feet, and could be worse if your altimeter is out of calibration.

Here's a simple web calculator which will work on your phone, at the airport. Seems to be pretty accurate.

http://www.csgnetwork.com/stationpressurecalc.html

Input the altimeter setting from your best local source (AWOS, ATIS, etc.) and the altitude where your airplane is parked. Tap calculate, and compare "station pressure" to your MP gauge, engine off. The calibration risk is the accuracy of your local FAA equipment.

I like this thank you. The plane is currently in North Carolina where I was doing these adjustments but will be here at home very soon when I fly it home after Oshkosh.

 

[Pilot135pd]

I was adjusting something else and I remembered this thread so I checked the local pressure and my field elevation and entered it in the page you gave me. The highest engine off manifold pressure I can get with adjustments on my MGL Extreme EMS is still 29.00