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  #21  
Old 12-30-2013, 10:17 AM
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Radomir Radomir is offline
 
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Jon,

LSE II+ is only $200 more than a 4370 mag (or $130 more than 4371). With 0.5 gph saving, you'd pay it off in a few months at most. And long term, the savings would be huge (ie you won't be spending $900 every 500-850 hrs).
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  #22  
Old 12-30-2013, 11:56 AM
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N941WR N941WR is offline
 
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Default A & B Curve Clarification

The following is to help you understand how the P-mags work. I will not comment on the actual Emag timing map as that is considered proprietary to Emag Ignitions and due to our relationship with them we promised that we would not publish their timing map/curve. What Brian has documented is the MAP's contribution to the timing curve. As you can imagine, those numbers are not always used to calculate the firing angle. In Brian's defense, the numbers he published at the start of this thread are what is reported by Emags EICAD program.

The P-mag has, in effect, two memory locations, A & B. Commonly called the “A Curve” and “B Curve”.

To switch between the two, a builder installs a jumper between pins #2 & #3 on the P-mag. The default, no jumper installed, is to run on the B Curve. Once the jumper is installed, the Pmags switch to the A curve. (When our EICommander is installed, no jumper is required. I will explain that later.)

The B Curve is fully configurable via Emag’s EICAD program or our EICommander. This discussion assumes an unmodified B Curve.

The A Curve, jumper installed, starts the timing at around 26* BTC and will allow the timing to advance up to 34* BTC, depending on RPM and MAP.

The B Curve, jumper NOT installed, adds a five degree shift to the A Curve. Thus timing starts at around 31* BTC and advances up to 39* BTC.

That is all in the Pmag manual, page 14 and mimics what we have found on our test stand and in actual flight conditions.

The pilot has the ability to adjust the max advance and the advance shift via the EICAD program or the EICommander. For example, if your engine requires a timing of 20*BTC, then you can enter in a negative shift and reduce the timing to 20* BTC and the max advance will also be reduced.

With this in mind, it should not surprise anyone who has read the manual that when operating with the B Curve (No jumper installed) under high power settings, such as during takeoffs, that the Pmag sets the timing at 31* BTC. With the jumper installed, the Pmag will set the takeoff timing to 26* BTC.

During the development of the EICommander, we took an old engine and cut the case in half and used that to spin two Pmags on our test bench. We discovered that there is so much gear slop in our drive trains that even standard magnetos vary by as much as 1.5*. This is really noticeable when running a light, composite propeller.

The idea of setting the timing one or two degrees after top dead (TDC) center is suggested by Emag for those who run composite propellers so the spark fires after the prop has crested TDC and the spark helps spin the prop. This may be necessary because when below 200 RPM’s the Pmags fire at TDC, not after TDC, and a light prop may not have the inertia to get past the compression stroke and spark plug firing when starting. Metal props don’t seem to have this problem. (For the record, I run the A curve and my TDC is set at zero for my O-360 with a Catto prop.)

EICommander
The EICommander that we produce is simply a piggy back unit for the Pmags. It can monitor the Pmags and display the current advance numbers (not the MAP contribution), along with any divergence in timing between two Pmags, the condition of the ignition harnesses and a number of other parameters.

When first installing an EICommander, the Pmags will automatically default to the B Curve. Thus, we recommend our clients send the P-mags the A Curve, if they want to run the A Curve. (New engines, or newly rebuilt engines should run the A curve for the first 10 to 15 hours and cap the advance to 26* BTC either via a custom EICommander configuration or by plugging the MAP lines to the Pmags.)

We tell clients to think of the Pmag as having two memory locations, A & B. The A location is fixed and cannot be changed. The B location is fully programmable and when the EICommander sends the A configuration to the P-mags it is actually stored in the B memory location. Thus, the A & B configurations are exactly the same at this point but because there is no jumper installed (or required), the Pmags will act like they are running the A Curve.

Should a client wish to create a custom “C” configuration (Say with a 20* BTC starting point), they simply send that to the Pmags and it will be stored in the “B” memory location. In other words, with the EICommander installed, the Pmag never use the “A” memory location, regardless of what configuration is sent the Pmags.
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Last edited by N941WR : 12-30-2013 at 12:04 PM.
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  #23  
Old 12-30-2013, 12:37 PM
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Brantel Brantel is offline
 
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Quote:
Originally Posted by N941WR View Post
The B Curve, jumper NOT installed, adds a five degree shift to the A Curve. Thus timing starts at around 31* BTC and advances up to 39* BTC.

That is all in the Pmag manual, page 14 and mimics what we have found on our test stand and in actual flight conditions.

With this in mind, it should not surprise anyone who has read the manual that when operating with the B Curve (No jumper installed) under high power settings, such as during takeoffs, that the Pmag sets the timing at 31* BTC.
My P-Mag out of the box had the following settings when I connect it to EICAD, they have not been modified:

ADV Shift = 5.6° not 5 (correction, it was actually 4.2°)

Max Adv = 40.6° not 39

The stock A curve minimum cannot be 26, it is either 25.2° or 26.6° due to the 1 byte resolution of the P-Mag processor and mine seems to be 26.6° (actually I think it is more like 28° based on my findings)

When running on the B curve, my minimum that I see is 32.2° which is the same as 28° (Base curve Min) + 4.2° (B Curve Constellation shift) That being said, my minimum advance data matches what I would expect it to based on the variables involved.

When running on the B curve, my maximum that I see is 40.6° which is the same as what EICAD says my Max Adv is set to.

Like I have said before, the manual is full of these kinds of inconsistencies due to rounding up and down and the fact that the processor has a low resolution to work with and what appears to be different defaults than what is in the book.

I don't understand why we you are recommending that we disregard the effect of the MAP sensor on the advance. Since the MAP sensor in the Pmag does effect the ultimate timing advance, why would we ignore that variable?

I stand by my chart....and based on the default settings and your second sentence above, your data also backs mine up within degree or so due to rounding/small errors.

My only point is this:

If one operates their P-Mag with the default settings on the "B" curve,
Their Max Advance is going to be 40.6° and it comes in pretty steep based on my charted data.
Their Minimum Advance is going to be 32.2° even under full power which is 7.2° more advance than the 25° standard from Lycoming. 12.2° more for those with engines recommending 20°.
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Lyc. O-360 carbed, HARTZELL BA CS Prop, Dual P-MAGs, Dual Garmin G3X Touch
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Last edited by Brantel : 12-31-2013 at 12:27 PM.
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  #24  
Old 12-30-2013, 12:50 PM
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AZtailwind AZtailwind is offline
 
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Quote:
Originally Posted by jthocker View Post
As I contemplate my overdue for inspection Slick mags.(850hrs), I wish I could get a real world comparison that I could trust. I am struggling with ROI in EI.
Mutha... or er, I mean, (scratch head) what's that new call sign again? Badger....

I wouldn't wait long on that Slick inspection- especially if that time above is more than SOH. Lost the slick after 1200 hours new and after a 600 hr inspection calling both slicks good. Pushed it too far.

Operating the 114 P-Mag in service now for more than 400 hours(sometimes in PHX extreme hot environments). A-curve operation only. Data shows a marginal fuel efficiency(carburated Parallel valve 180) .5 gal hr but with some ability to run LOP if I must. Smother running engine with cheap plugs also. Yes the ROI is probably over a longer haul with the FI you already have.
My engine is hotter, even with the A-curve and the #3Cyl baffle mod. So I'm real interested in Brantel's next test.
Thanks for data!
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  #25  
Old 12-30-2013, 02:27 PM
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DanH DanH is offline
 
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Quote:
Originally Posted by N941WR View Post
What Brian has documented is the MAP's contribution to the timing curve. As you can imagine, those numbers are not always used to calculate the firing angle. In Brian's defense, the numbers he published at the start of this thread are what is reported by Emags EICAD program.
I think you're saying is the values reported by Brian are in fact the actual firing angles with the manifold pressure line connected. Correct?

The manual (page 15) says

2. Test with (near) standard magneto timing. With the ignition indexed
at TDC and using the A curve, you can disconnect the MAP tube from
the ignition(s). In this configuration, the maximum advance will be near
standard mag timing (26 degrees).


Does this mean that when operated with the manifold pressure line disconnected, timing will be fixed throughout the RPM range, just as a mag is fixed?
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  #26  
Old 12-30-2013, 02:44 PM
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Brantel Brantel is offline
 
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Quote:
Originally Posted by DanH View Post
I think you're saying is the values reported by Brian are in fact the actual firing angles with the manifold pressure line connected. Correct?

The manual (page 15) says

2. Test with (near) standard magneto timing. With the ignition indexed
at TDC and using the “A” curve, you can disconnect the MAP tube from
the ignition(s). In this configuration, the maximum advance will be near
standard mag timing (26 degrees).


Does this mean that when operated with the manifold pressure line disconnected, timing will be fixed throughout the RPM range, just as a mag is fixed?
When you disconnect the MAP line, the PMag assumes that the engine is at max power regardless of the RPM. The max advance will be:

26.6° when running the "A" curve (actually I think this is more like 28° based on my findings)
28° + "Adv Shift" (Constellation Shift) default of 4.2° = 32.2° when running on a default "B" curve

You can also set the "Max Adv" to limit the Pmag from advancing above that variable.
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Brantel (Brian Chesteen),
Check out my RV-10 builder's BLOG
RV-10, #41942, N?????, Working on Emp/Tail Cone
---------------------------------------------------------------------
RV-7/TU, #72823, N159SB
Lyc. O-360 carbed, HARTZELL BA CS Prop, Dual P-MAGs, Dual Garmin G3X Touch
Track N159SB (KK4LIF)
Like EAA Chapter 1494 on Facebook

Last edited by Brantel : 12-31-2013 at 12:31 PM.
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  #27  
Old 12-30-2013, 03:54 PM
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N941WR N941WR is offline
 
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Quote:
Originally Posted by DanH View Post
I think you're saying is the values reported by Brian are in fact the actual firing angles with the manifold pressure line connected. Correct?
No, not correct. If you take Brian's numbers, the engine would be firing at very high firing angles when under low power. At higher power, he is close. The numbers he presented, as read from the EICAD program, are simply used to calculate the firing angle, they are not the actual firing angle.

Quote:
Originally Posted by DanH View Post
The manual (page 15) says

2. Test with (near) standard magneto timing. With the ignition indexed
at TDC and using the A curve, you can disconnect the MAP tube from
the ignition(s). In this configuration, the maximum advance will be near
standard mag timing (26 degrees).


Does this mean that when operated with the manifold pressure line disconnected, timing will be fixed throughout the RPM range, just as a mag is fixed?
Correct, it fixes the timing at the lower setting. In Brian's example, should the MAP line come disconnected, the timing will be fixed at 32* BTC.

That is why I recommend people with new or newly overhauled engines to set them to the A curve and to plug the MAP line for the first 10 to 15 hours. That will fix the timing at 26* BTC and force the P-mag to act like a standard mag until the rings are set. This will help remove the P-mags from any high CHT issues the builder might have and hopefully point them towards their baffles.
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RV-9 (Yes, it's a dragon tail)
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SC86 - Easley, SC
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  #28  
Old 12-30-2013, 03:57 PM
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N941WR N941WR is offline
 
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Quote:
Originally Posted by Brantel View Post
My P-Mag out of the box had the following settings when I connect it to EICAD, they have not been modified:

ADV Shift = 5.6 not 5

Max Adv = 40.6 not 39

The stock A curve minimum cannot be 26, it is either 25.2 or 26.6 due to the 1 byte resolution of the P-Mag processor and mine seems to be 26.6

When running on the B curve, my minimum that I see is 32.2 which is the same as 26.6 (A curve Min) + 5.6 (B Curve Constellation shift) That being said, my minimum advance data matches what I would expect it to based on the variables involved.

When running on the B curve, my maximum that I see is 40.6 which is the same as what EICAD says my Max Adv is set to.

Like I have said before, the manual is full of these kinds of inconsistencies due to rounding up and down and the fact that the processor has a low resolution to work with and what appears to be different defaults than what is in the book.

I don't understand why we you are recommending that we disregard the effect of the MAP sensor on the advance. Since the MAP sensor in the Pmag does effect the ultimate timing advance, why would we ignore that variable?

I stand by my chart....and based on the default settings and your second sentence above, your data also backs mine up within degree or so due to rounding/small errors.

My only point is this:

If one operates their P-Mag with the default settings on the "B" curve,
Their Max Advance is going to be 40.6 and it comes in pretty steep based on my charted data.
Their Minimum Advance is going to be 32.2 even under full power which is 7.2 more advance than the 25 standard from Lycoming. 12.2 more for those with engines recommending 20.
You are correct in that the manual rounds out the numbers. The numbers I shared came right from their manual and very closely match what we have seen (rounded, of course). As I said, I will not divulge their timing curve.

At lower power settings, the standard "B Curve" will never see 40.6* BTC because they set the max advance number.
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  #29  
Old 12-30-2013, 03:59 PM
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mburch mburch is offline
 
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Quote:
Originally Posted by N941WR View Post
The numbers he presented, as read from the EICAD program, are simply used to calculate the firing angle, they are not the actual firing angle.
Hmm. Put me down in the "sure would like to know what the full-power timing on my expensive engine is actually going to be" column.

Quote:
Originally Posted by N941WR View Post
That is why I recommend people with new or newly overhauled engines to set them to the A curve and to plug the MAP line for the first 10 to 15 hours. That will fix the timing at 26* BTC and force the P-mag to act like a standard mag until the rings are set.
Bill, just checking, did you really mean plug the MAP line, or did you mean just disconnect it as stated in the manual? Seems like it could mean two different things, assuming the P-mag's sensor is sealed up internally.

thanks,
mcb
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Last edited by mburch : 12-30-2013 at 04:07 PM. Reason: typo
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  #30  
Old 12-30-2013, 04:04 PM
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N941WR N941WR is offline
 
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Quote:
Originally Posted by mburch View Post
Hmm. Put me down in the "sure would like to know what the full-power timing on my expensive engine is actually going to be" column.
At full power; down low with high MAP, you will run the minimum advance as configured in your P-mag. (A vs. B curve) The P-mags, under these conditions, does not add anything to the firing angle. The reason, as you can imagine, is to keep from damaging your engine.

Quote:
Originally Posted by mburch View Post
Bill, just checking, did you really mean plug the MAP line, or did you mean just disconnect it as stated in the manual? Seems like it could two different things, assuming the P-mag's sensor is sealed up internally.

thanks,
mcb
Yes, plug your MAP lines; both the line that goes to your P-mag and the one going to your MAP sensor. This assumes they are staying low for the first 10 - 15 hours. You could leave the P-mag MAP line open. (We did have one client that took his plane up above 6,000' with the P-mag MAP line plugged and it worked like a balloon and he saw his advance change.) The goal is to trick the P-mags into acting like a standard mag and not advance.

After you get 10 to 15 hours on your engine, then play around with the B curve, if you want. Just remember, it starts out at 32* BTC.
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RV-9 (Yes, it's a dragon tail)
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SC86 - Easley, SC
www.repucci.com/bill/baf.html

Last edited by N941WR : 12-30-2013 at 04:08 PM.
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