E-mag question (probably stupid)

[witek]

Hi All,

As a starting point I want to use timing recommended by producer. It means I want to use the jumper to setup the timing and reduce the advance range by 4.2 degrees.
Question - should the jumper stay installed only during the ignition timing procedure and removed after the procedure is finished or permanently during the normal operation?

Thanks,
Witold

 

[wirejock]

P-mag timing

Hi All,

As a starting point I want to use timing recommended by producer. It means I want to use the jumper to setup the timing and reduce the advance range by 4.2 degrees.
Question - should the jumper stay installed only during the ignition timing procedure and removed after the procedure is finished or permanently during the normal operation?

Thanks,
Witold

You want to retard the timing by 4.2°?
Just making sure.
If the jumper is installed, the P-mags run the "A" curve. So if you want the manufacturer timing curve, leave the jumper in place. If you want anything else, the jumper must be removed and the P-mags programmed for a "B" curve. The P-mag will run the "B" curve if the jumper is absent.
Personally, I ran the cable inside and installed a D-sub on each with a jumper. Plan is to program the "B" curve to match so no matter what, they will run the "A" curve timing. I ran the cable inside so I could access them for download.

 

[Larco]

For timing curve A leave the jumper in. Leaving it out gives you timing curve B.

 

[penguin]

Hi All,

As a starting point I want to use timing recommended by producer. It means I want to use the jumper to setup the timing and reduce the advance range by 4.2 degrees.
Question - should the jumper stay installed only during the ignition timing procedure and removed after the procedure is finished or permanently during the normal operation?

Thanks,
Witold

Leave the jumper in at all times.

 

[Carl Froehlich]

Hi All,

As a starting point I want to use timing recommended by producer. It means I want to use the jumper to setup the timing and reduce the advance range by 4.2 degrees.
Question - should the jumper stay installed only during the ignition timing procedure and removed after the procedure is finished or permanently during the normal operation?

Thanks,
Witold

The statement does not make much sence.

Timing the pMag:
- Parallel valve engine. Set the crank to TDC and follow the pMag install instructions. This sets the pMag to the engines base timing of 25* BTDC.
- Angle head engines. Set the crank to 5* ATDC. This sets the pMag to the engine base timing of 20* BTDC.

For 99% of RVs the jumper should alway be installed. This provides a maximum of 9 degree of advance (high altitude, low MP conditions). Jumper out gives 14 degrees of advance. All my experience with pMag tells me there is a gain with jumper in. Jumper out there is no more gain, just higher CHTs.

Carl

 

[rv8ch]

...
Question - should the jumper stay installed only during the ignition timing procedure and removed after the procedure is finished or permanently during the normal operation? ...

Leave in the jumper. The device looks at this every boot, not just when it's being configured.

I would also recommend getting either an EICommander or an EngineBridge so you will have more information about what's happening in your ignitions.

 

[Ezburton]

The statement does not make much sence.

Timing the pMag:
- Parallel valve engine. Set the crank to TDC and follow the pMag install instructions. This sets the pMag to the engines base timing of 25* BTDC.
- Angle head engines. Set the crank to 5* ATDC. This sets the pMag to the engine base timing of 20* BTDC.

For 99% of RVs the jumper should alway be installed. This provides a maximum of 9 degree of advance (high altitude, low MP conditions). Jumper out gives 14 degrees of advance. All my experience with pMag tells me there is a gain with jumper in. Jumper out there is no more gain, just higher CHTs.

Carl

Why should the angle valve engines be timed at 5 ATDC? I didn't see anything about this in the setup instructions.

They do say to do this if your mag timing is supposed to be 20, but I have an angle valve engine which is timed at 25.

From the manual...
Examples
25-Degree data plate engines (typical of Lyc 320, 360) could start with 1) Jumper IN and 2) TC
Offset position at TC. High-power firing will be roughly 25-degrees. Cruise firing will be roughly 34-
degrees.
20-Degree data plate engines (typical of Lyc 390) could start with 1) Jumper IN, and 2) TC Offset at
4 to 5-degrees after TC. High-power firing will be roughly 20-degrees. Cruise firing will be roughly
29-degrees.

 

[Taltruda]

Why should the angle valve engines be timed at 5 ATDC? I didn't see anything about this in the setup instructions.

They do say to do this if your mag timing is supposed to be 20, but I have an angle valve engine which is timed at 25.

From the manual...
Examples
25-Degree data plate engines (typical of Lyc 320, 360) could start with 1) Jumper IN and 2) TC
Offset position at TC. High-power firing will be roughly 25-degrees. Cruise firing will be roughly 34-
degrees.
20-Degree data plate engines (typical of Lyc 390) could start with 1) Jumper IN, and 2) TC Offset at
4 to 5-degrees after TC. High-power firing will be roughly 20-degrees. Cruise firing will be roughly
29-degrees.

I thought all angle valve engines are 20 degrees? But maybe not.. which model engine do you have? Your data plate says 25?

https://www.lycoming.com/sites/defa...20Approved%20Slick%20Magnetos%20and%20EIS.pdf

 

[vlittle]

I thought all angle valve engines are 20 degrees? But maybe not.. which model engine do you have? Your data plate says 25?

https://www.lycoming.com/sites/defa...20Approved%20Slick%20Magnetos%20and%20EIS.pdf

And not all parallel valve engines are set at 25 degrees. The advance is specified on the engine data plate. Follow the PMAG installation manual. Higher compression engines often retard the nominal timing.

As for the jumper in or out, I have put in a switches for this. It also allows me to control the PMAGs from an external source (EICAD, or a custom design (cough)).

 

[calpilot]

The statement does not make much sence.

Timing the pMag:
- Parallel valve engine. Set the crank to TDC and follow the pMag install instructions. This sets the pMag to the engines base timing of 25* BTDC.
- Angle head engines. Set the crank to 5* ATDC. This sets the pMag to the engine base timing of 20* BTDC.

For 99% of RVs the jumper should alway be installed. This provides a maximum of 9 degree of advance (high altitude, low MP conditions). Jumper out gives 14 degrees of advance. All my experience with pMag tells me there is a gain with jumper in. Jumper out there is no more gain, just higher CHTs.

Carl

Give Brad at Emagair a call!!!! I am running a parallel valve injected 360, 9:1 pistons, ventury cut seats, performance camshaft, that said, it produces more power then the original 180HP, therefore, the detonation boundary at full advance is very narrow, so like many with "pumped up" engines or stock angle valve IO-360 or IO-390, Brad recomends retarding the timing to -5 BTDC. Each flywheel tooth is 2.4 degrees, I did a very careful before and after look see at the operating indicatiions. with the two tooth retard, my engine runs smoother, cooler, and did not loose any speed in cruise. The reduction aone for CHT indicated that I was running close to detonation boundary.
DAR Gary

 

[bjdecker]

Give Brad at Emagair a call!!!! I am running a parallel valve injected 360, 9:1 pistons, ventury cut seats, performance camshaft, that said, it produces more power then the original 180HP, therefore, the detonation boundary at full advance is very narrow, so like many with "pumped up" engines or stock angle valve IO-360 or IO-390, Brad recomends retarding the timing to -5 BTDC. Each flywheel tooth is 2.4 degrees, I did a very careful before and after look see at the operating indicatiions. with the two tooth retard, my engine runs smoother, cooler, and did not loose any speed in cruise. The reduction aone for CHT indicated that I was running close to detonation boundary.
DAR Gary

"Generalizations are always bad." - Anonymous

2.41° per tooth is for a 149 tooth flywheel, 2.95° per tooth for a 122 tooth flywheel.

Spark Advance as measured from TDC is going to depend (largely) upon the compression ratio of the pistons. ergo 8.5:1 => 25°BTDC, 8.7:1 => 20°BTDC, 9:1 => 19°BTDC, 10:1 => 17°BTDC.

Choosing a timing that is more than the aforementioned will result in higher CHTs and reduced detonation margin.

The 5° value (2-ish teeth on a 149 tooth ring) is the equivalent of 20° BTDC (#1 cylinder, stamped into the backside of the flywheel on Lyco's -- not sure about clones.).