P-mag Timing Explained

[jeffw@sc47]

The EIC has one male D-sub connector. How do I wire two P-mags to interface?

I have already wired up two D-subs, one for each P-mag, to interface to use the EICAD program initially.

[N941WR]

Originally Posted by jeffw@sc47

The EIC has one male D-sub connector. How do I wire two P-mags to interface?

I have already wired up two D-subs, one for each P-mag, to interface to use the EICAD program initially.

Jeff, just make a Y adapter that comes from each DB9 connector to the DB15 connector required by the EIC.

Did you bring the tach line to each of the DB9 connectors? That is required.

[jeffw@sc47]

Yes, I brought both tach inputs to each the separate DB9's.

So, each separate P-mag is distinguishable when Y-wired to one DB9 connector brought to the EIC?

Is that also the case when connected to a PC?

[Raymo]

Originally Posted by jeffw@sc47

So, each separate P-mag is distinguishable when Y-wired to one DB9 connector brought to the EIC?

Is that also the case when connected to a PC?

The two DB9s are connected to a DB15, which connects to the EIC. You could, optionally, connect them directly to the DB15 but would not then be able to connect individually to a PC, if later desired.

[N941WR]

Ray is correct.

The PC USB to serial converters are DB9 connectors. You can plug a PC in to either P-mag, as needed.

Had you wired your P-mags to one DB15 connector and wanted to use a PC withe the EICAD program, you would have to make a reverse Y cable to go from the DB15 to two DB9 plugs.

[Aggie78]

Originally Posted by Scott Hersha

This all assumes I?m good at setting my timing mark at 1.5* after TDC. I didn?t have a propeller protractor to do this, so my method of measurement might be a little crude.

Scott (and Bill),

So, I?m about to embark on installing the 2nd Pmag on my aircraft (have been running 1 on the left/Slick on the right for the last 3 years) and I am following the information on this thread closely and intend to set the timing up on BOTH as you did and as Bill recommends (1.4* shifted).

Regarding measurement of that 1.4*, would a circular protractor, downloaded, printed out and attached to the flywheel be (perhaps) a more accurate way of measuring?

This website:

https://www.blocklayer.com/protractor-printeng.aspx

...Allows you to create a template up to 30? in diameter. My thoughts would be to print an appropriately sized, anti-clocked, circular protractor, attach it to the flywheel and then use it as accurately as I can to set the mags after moving it 1.4* after TDC.

More or less accurate than counting teeth or am I being overly detail-oriented in this? Just count teeth, set the mags and it?ll be fine?

Thanks,

Rob S.

[Scott Hersha]

Rob,
That protractor should work as long as the printed copy is true. You should check it with a simple plastic protractor. Another possibility would be to use your cell phone with an angle finder app, or level app. My iPhone has one. Tape it to your prop at TDC, zero the digital readout on the app, and then move the prop 1.4*. Make sure you go the correct direction (counter-clockwise looking at it from the front - aft), so you are retarding the timing v.s. advancing it.

[Aggie78]

Originally Posted by Scott Hersha

Rob,
That protractor should work as long as the printed copy is true. You should check it with a simple plastic protractor. Another possibility would be to use your cell phone with an angle finder app, or level app. My iPhone has one. Tape it to your prop at TDC, zero the digital readout on the app, and then move the prop 1.4*. Make sure you go the correct direction (counter-clockwise looking at it from the front - aft), so you are retarding the timing v.s. advancing it.

Brilliant!

In 30 seconds, I downloaded and installed a free protractor app that will do the trick just as you described!

Outstanding tip, Scott! Thanks!!

Rob

[WingnutWick]

Unless I?m missing something, I?m pretty sure the 1.4 shift is done through the Emag program and not by setting the actual past TDC. For the 0-360s I think it?s reccomended to electronically shift the curve 1.4 via the software while timed at TDC. So as long as you have a TDC mark, you shouldn?t need to do any of this protractor measuring. Electronically shifting the curve 1.4 via the software is not the same as timing the Pmags to 1.4 past TDC.

Originally Posted by Aggie78

Scott (and Bill),

So, I?m about to embark on installing the 2nd Pmag on my aircraft (have been running 1 on the left/Slick on the right for the last 3 years) and I am following the information on this thread closely and intend to set the timing up on BOTH as you did and as Bill recommends (1.4* shifted).

Regarding measurement of that 1.4*, would a circular protractor, downloaded, printed out and attached to the flywheel be (perhaps) a more accurate way of measuring?

This website:

https://www.blocklayer.com/protractor-printeng.aspx

...Allows you to create a template up to 30? in diameter. My thoughts would be to print an appropriately sized, anti-clocked, circular protractor, attach it to the flywheel and then use it as accurately as I can to set the mags after moving it 1.4* after TDC.

More or less accurate than counting teeth or am I being overly detail-oriented in this? Just count teeth, set the mags and it?ll be fine?

Thanks,

Rob S.

[Aggie78]

Originally Posted by WingnutWick

Unless I’m missing something, I’m pretty sure the 1.4 shift is done through the Emag program and not by setting the actual past TDC. For the 0-360s I think it’s reccomended to electronically shift the curve 1.4 via the software while timed at TDC. So as long as you have a TDC mark, you shouldn’t need to do any of this protractor measuring. Electronically shifting the curve 1.4 via the software is not the same as timing the Pmags to 1.4 past TDC.

Wick,

Go back to page 1, first post and scroll down to where Bill talks about "clocking" the mags....

That's what is being discussed here...physically advancing the engine 1.4* past TDC and then setting the timing of the Pmags there via the instructions found in their manual.

Measuring and setting that 1.4* is what I'm using the protractor for.
-Rob