E/P mag "A" verses "B" timing curve?

[Steve Brown]

When I got my airplane back together after getting the E/P mags serviced the airplane ran fine, but different. Power seemed ok, but it sounded different, CHTs were higher, and it seemed more difficult to run LOP.

Email exchange with the builder confirmed he was running custom timing somewhere between the A & B default settings. I had run the standard "B" curve.

Last weekend I put the jumper in to run the "A" curve. CHTs came down and running LOP was easier. However, it seemed to run a little rougher at very low power settings like idol, landing, etc.

OAT was a lot higher during the "A" test, so that could be affecting results and my perceptions. Since all of this is based on my subjective perception so I'm wanting to get (me) calibrated.

Is this expected?

According to what I heave read, the CHT change is expected, but I didn't read anything about LOP operation.

Any E/P Mag users who have experimented with A verses B I like to hear your observations. Also, I guess timing is generic, so generic timing expectations would also be helpful.

Honestly, I could live with either A or B standard setting, but while I'm messing with it I figure I might as well do what makes the most sense. I'm considering custom timing, or just being able to switch between A & B.

[N941WR]

Steve,

The "B" curve is something that can be set by the user. In other words, there is really no default "B" curve.

Connect to both E & P mags with the EICAD software and verify the timing shift of the "B" curve. Brad does a great job but I would want to verify the timing shift after having them serviced.

Also, we are developing an instrument to allow you to monitor and control the 113 & 114 E and P model ignitions from the cockpit. Our web site is www.eicommander.com, let me know if you are interested.

[Steve Brown]

Originally Posted by N941WR

Steve,

The "B" curve is something that can be set by the user. In other words, there is really no default "B" curve......

My understanding is based on the manual:
"A Closer Look: Series 113 ignitions use a Base Table to determine ignition timing. The Base Table uses rpm and manifold pressure to assign a firing angle. The ignition also has provision for applying an ?Advance Shift? to the Base Table. When told to do so, the ignition will shift (advance or retard within preset limits) the Base Table firing angle by the value stored in the Advance Shift.
? The ?A? curve (referenced elsewhere in this manual) is the Base Table itself. Placing a jumper between terminals #2 and #3 of the control plug tells the ignition (at power up) to look at the Base Table alone for firing angle.
? The ?B? curve is the Base Table with the Advance Shift applied. The factory default Advance Shift is ?+5?. Removing the jumper tells the ignition (at power up) to apply the Advance Shift value to the Base Table.
Using EICAD, you can replace the factory default Advance Shift (+5) with a figure anywhere between (-12) to (+12) degrees. There are, however, factory min/max limits (not adjustable by the customer) set at 20 and 39 degrees respectively. This keeps the firing angle inside the range of settings that are 1) called out by some
engine (magneto) installations as a minimum, and 2) no more than our factory default (39 degree max) curve ? see chart below. After EICAD stores an Advance Shift value, the PC (lap top) can be removed."

According to the manual, there is a default "B" curve which will be used with the jumper removed. However, the B curve can be replaced by the user.
Is the Emag manual in error or am I reading it wrong?

[Bob Martin]

Originally Posted by N941WR

Steve,

The "B" curve is something that can be set by the user. In other words, there is really no default "B" curve.

Connect to both E & P mags with the EICAD software and verify the timing shift of the "B" curve. Brad does a great job but I would want to verify the timing shift after having them serviced.

Also, we are developing an instrument to allow you to monitor and control the 113 & 114 E and P model ignitions from the cockpit. Our web site is www.eicommander.com, let me know if you are interested.

Bill, It appears the manual says there is a B curve.

From the P-mag install manual online--on Emagair.com
Snip
EICAD allows builders to adjust:
Advance Shift- Programmable Advance Shift simply expands the range of settings beyond the two “A” and “B” factory preset positions. We expect most customers will find the A and B curves meet their needs,

The “A” curve (referenced elsewhere in this manual) is the Base Table itself.
Placing a jumper between terminals #2 and #3 of the control plug tells the
ignition (at power up) to look at the Base Table alone for firing angle
assignments.
The “B” curve is the Base Table with the Advance Shift applied. The factory default Advance Shift is “+5”. Removing the jumper tells the ignition (at power up) to apply the Advance Shift value to the Base Table.
Snip

I know you are a avid user of the P-mag and the B curve is adjustable by using EICAD, but from what I read in the manual, a P-Mag owner/user doesn't have to use EICAD if he is happy with standard programed A & B timing curves. Am I missing something too?

I want to be a P-mag believer and user one day.....I'm watching others experiances with them closely.........I do like the control module you are developing.........so add me to the interested list!

ps...seems Steve and I were typing at the same time and were thinking the same thing.

[randylervold]

Originally Posted by Bob Martin

I want to be a P-mag believer and user one day.....I'm watching others experiances with them closely.

Me too, and I have several friends who are considering switching to the Emag/Pmag system also.

[N941WR]

Originally Posted by Bob Martin

...The “B” curve is the Base Table with the Advance Shift applied. The factory default Advance Shift is “+5”. Removing the jumper tells the ignition (at power up) to apply the Advance Shift value to the Base Table.
Snip

I know you are a avid user of the P-mag and the B curve is adjustable by using EICAD, but from what I read in the manual, a P-Mag owner/user doesn't have to use EICAD if he is happy with standard programed A & B timing curves. Am I missing something too?

I want to be a P-mag believer and user one day.....I'm watching others experiances with them closely.........I do like the control module you are developing.........so add me to the interested list!

ps...seems Steve and I were typing at the same time and were thinking the same thing.

Bob,

Yes, that is correct but what you need to understand is that "B" curve can be adjusted up or down whereas the "A" curve is fixed.

After rereading the original post, I realized the builder had shifted the "B" curve down from the factory default.

The factory default shift value for the "B" curve is around 4.2 to 4.5 degrees with a max advance of 41 degrees. However, these can be changed by the user, as were done by the builder.

To set the E/P-mags close to where the builder had set them "Between the A & B curve" he will need to use EICAD program and using the arrow keys to shift the curve down to the 2.? range. There is probably no reason to change the max advance but that can be dialed down some, if desired. (The A max advance is around 34 degrees.)

All that can be done via the EICAD program availble from the E-MAG Ignition's web site. you will need a three wire serial connection to communicate with the E & P-mags; ground, send, & receive. (DB9 connection from the computer: Pin 2 - Receive, Pin 3 - transmit, & Pin 5 - Ground)

Bob & Randy, keep the faith. These things really are good ignitions and once you understand how they work, all is good.

Let me know if you have any other questions.

[frankh]

After a previous upgrade I do seem to remember my B curve had shifted...Probably back to the factory settings but I can't honestly remember.

I do remember going back into the EICAD to adjust my b curve such that is gave a max advance of 25 degrees..I did this for use with mogas,...In the end it proved not to be necesary so I "THINK" I am back on A curve timing for mogas...Don't take that as Gospel though!

Frank