P-Mag "B" Curve Advance Map

[Brantel]

I decided today was the day to put the P-Mag monitor that I built a couple years ago to the test and use it to map out the advance curve on the P-Mag. (Dan Horton suggested this in another thread)

This is a P-Mag set to the factory settings using the "B" curve and the manifold pressure line is connected.

Hope this helps settle some dust around the mysterious P-Mag advance curve.



One thing that I noticed is how the P-Mag is advancing the timing even at high power settings by about 7°. Based on the info David (RV10inOz) has been providing I am definitely going back to the "A" curve and may make more drastic changes with the software..... I have always had to limit climbs due to hitting my personal limit of 410°, this may help.

[rzbill]

I am just an observer in regards to EI, but I thought that the bottom right of the chart was supposed to be populated with 25 degree timing for either A or B curves.
Thanks for the data Brian

[Brantel]

Originally Posted by rzbill

I am just an observer in regards to EI, but I thought that the bottom right of the chart was supposed to be populated with 25 degree timing for either A or B curves.
Thanks for the data Brian

The B curve is offset no matter what by the amount entered into "adv shift/constellation shift" field inside EICAD or with Bill's EICommander.

I chose an RPM and MP range that a typical RV may use. I have no idea if the advance would go lower at RPMs and MP off of my chart but I really am not interested in those areas since I never operate there.

I can tell you that I was shocked to see it advancing over 7 degrees on a full power climbout at my field altitude but I should not have been. The manual spells this out pretty clear. If I had noticed this before, I would not have been using the B curve all along. My mistake for not reading the manual well enough.

[rocketbob]

Holy cow!

There's no good reason to have ANY advance at full power.

[Brantel]

Originally Posted by rocketbob

Holy cow!

There's no good reason to have ANY advance at full power.

I agree. These EI makers need to make their default timing MAPs available so that people don't have to go thru this to understand what their ignition is doing.

I have no idea why I waited so long to do this after installing the CS prop, I should have done it sooner. It would have been real hard to impossible to do with the FP prop.

[Brantel]

Oh and I can tell you the engine does not like being forced to 1800 RPM at 23-27" MP. At least it did not feel comfortable to me!

[mburch]

Say Brian, would you happen to also have a similar chart for the "A" curve? Or perhaps Emag makes that available somewhere and I've just missed it... there is a chart printed in the install manual, but it says something like "for illustration only, does not represent actual timing curve".

mcb

[Brantel]

Not yet Matt but I plan to map out the "A" curve next flight.

Emagair has never made these maps public to the best of my knowledge.

[N941WR]

Originally Posted by rocketbob

Holy cow!

There's no good reason to have ANY advance at full power.

The manual states the B curve simply shifts the entire curve 5 degrees

[Brantel]

Originally Posted by N941WR

The manual states the B curve simply shifts the entire curve 5 degrees

The manual contradicts itself and is inconsistent in several places as well as does not match the real world data.

One reason I decided just to map the curve myself.