PMAG Install

I am trying to install a new PMag on the 390. It came with one and I am installing the other one. I note the gear in the motor has 2 dots around the teeth where it looks to be timed. But the PMag has no dots on the gear. So I put it in and tightened it down. Without any timing involved.
Is this correct? Is all the timing set by the "blow" method described in the manual?
Thanks, Larry

Correct. Install the pMag and orientated it in a convenient position.

Reminder - for the IO-390 you set the pMag timing with the crank at 5 degrees ATDC, not TDC. Recommend having the jumper in.

Also remember you need long reach plugs for this engine - such as the Denso IKH27.

Please read the P-mag manual. The installation instructions are clearly described in there.

This is your ignition you are dealing with and if you get it wrong, you can damage your engine and possibly injure yourself.

BTW, 5° ATDC is different than 5 teeth. You definitely want the jumper in.

Please read this thread and contact me, if you have any questions.

http://www.vansairforce.com/community/showthread.php?t=167948

In addition to Carl's reminder, also remember that the IO390 is based on 20 BDC timing where as the plain and unchanged (via programming) PMAG will fire at 25 BDC, so you will need to account for that.

Bavafa said:

In addition to Carl's reminder, also remember that the IO390 is based on 20 BDC timing where as the plain and unchanged (via programming) PMAG will fire at 25 BDC, so you will need to account for that.

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Correct - thus the reason to set timing at 5 degrees ATDC for the IO-390. This yields the standard 20 degrees BTDC timing for this engine.

Carl

Bavafa said:

In addition to Carl's reminder, also remember that the IO390 is based on 20 BDC timing where as the plain and unchanged (via programming) PMAG will fire at 25 BDC, so you will need to account for that.

Click to expand...

Actually, if set to TDC with the jumper in, the P-mags will fire at 26.6?, almost 27?.

That is why I strongly recommend they be configured to match your engine.

N941WR said:

Actually, if set to TDC with the jumper in, the P-mags will fire at 26.6?, almost 27?.

That is why I strongly recommend they be configured to match your engine.

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Interesting, i spoke to Brad yesterday, he definetly said it's going to fire ffrom 25 to 26 degrees. With 1.4? resolution, it is consistent with 1.4*18 = 25.2, not 26.6!

isosceles said:

Interesting, i spoke to Brad yesterday, he definetly said it's going to fire ffrom 25 to 26 degrees. With 1.4° resolution, it is consistent with 1.4*18 = 25.2, not 26.6!

Click to expand...

I can assure you that the jumper in "A curve", we prefer the term "configuration", fires at 26.6 degrees when timed at TDC.

With the EICommander or Emag's EICAD program, you can see exactly where the A configuration is set to fire and I can assure you, it fires at 26.6*, not 25.2 for high power operation.

That is why we recommend they either be clocked or the configuration changed and lowered by a -1.4 for takeoff and reduced by the same amount on the Max Advance for parallel valve engines. By doing so, the engine runs cooler and you will pick up a couple of knots.

The real challenge is angle valve engines. By design, they run much cooler than parallel valve engines. Thus, if they run the standard A configuration, they don't see the CHT issues the parallel valve engines do; however, they still need to either clock or configure their P-mags so they fire at either 19.6 or 21 degrees for high power operations.

Please read this thread and watch the video: http://www.vansairforce.com/community/showthread.php?t=167948

I also sent you a PM.