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P-mag timing question. urgent!

Flyguytki

Well Known Member
When timing p-mags does cylinder one have to be at TDC or can it be one of the other cylinders? The manual simply states rotate propeller to TDC.
 
any

Any cylinder will do!!!!

CORRECTION: You may time the PMag on either Cylinder #1 or #2 at TDC, compression or exhaust stroke does not matter. Verify TDC with mark on starter ring gear.
 
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Mark on the flywheel

there is a mark for TDC on the flywheel as I remember.

I used the blow in the tube method but went away from that this last time.. just seemed an extra thing that might go wrong.. so I cleared the timing to its native timing, then set it up as close as I could.

Then I did the blow in the tube but it was only a fraction of a degree difference.

Frank
 
Whoa!

Any cylinder will do!!!!

I don't think that is correct. Number one can be on either the compression or exhaust stroke but it needs to be on one or the other. I don't think timing it with number three or four at TDC will work. It may work with number two at TDC but why do that. Just put Number one at TDC and blow in the tube. I may be wrong but if you could time it on any cylinder, then why would you have two coil banks? I'd either check deeper into this or just use number one to time your PMags. Good luck.
 
#1 cylinder TDC - does not matter if on compression or exhaust stroke. The ring gear will be marked on the engine side to line up with the top split line of the case, or the propeller side will be marked to align with a pin inserted into the starter nose case.

There is no longer a "native" timing on the PMags... The "blow" method is the way to time them now. you can find what appears to be a "native" timing, but it is in fact a completely random artifact of the software.
 
P-Mag timing

#1 cylinder TDC - does not matter if on compression or exhaust stroke
Is correct.
Make sure you are spinning the prop in the direction of rotation before stoping at the TDC position. Don't spin the prop beyond TDC and back it up. That would put back lash in the timing gears which would give you an error in timing.
 
From the manual

I don't think that is correct. Number one can be on either the compression or exhaust stroke but it needs to be on one or the other. I don't think timing it with number three or four at TDC will work. It may work with number two at TDC but why do that. Just put Number one at TDC and blow in the tube. I may be wrong but if you could time it on any cylinder, then why would you have two coil banks? I'd either check deeper into this or just use number one to time your PMags. Good luck.

From the 114-Series Installation manual:
"-Rotate your prop to the engine TDC (or TC) timing mark (see exception
Note 4) . By approaching this mark with the prop moving in the direction of
normal engine rotation you can minimize play in the gears.

Note 2: It does not matter whether the engine is on the compression or
exhaust stroke for a particular cylinder. "
 
It seems everyone is correct, as long as it is at TDC for any one of the cylinders you are good to go, We retimed the mags during troubleshooting this weekend after I had my first flight adventure on saturday and this was the main questions that came up, does it matter which. The answer is No it does not matter.
 
It does matter!

It seems everyone is correct, as long as it is at TDC for any one of the cylinders you are good to go, We retimed the mags during troubleshooting this weekend after I had my first flight adventure on saturday and this was the main questions that came up, does it matter which. The answer is No it does not matter.

I just called my friend, Brad, over at EMag. We had a long discussion and the answer is it does matter. You could time it with either 1 or 2 at TDC which is going to be the same. However, you can not time it with 3 and 4 at TDC. Time it with the TDC mark. Compression or exhaust doesn't matter but DON'T time it with 3 and 4 at TDC. I hope this helps.
 
Waste spark

The confusion may be due to the "wasted spark". It fires every time the piston reaches TDC ( plus the appropriate advance) so as long as you use the TDC mark on the flywheel (case split-backside or starter hole-front side) your fine.
The flywheel TDC mark refers to #1, but we don't care if its on compression or power stroke.

Tim
 
Learn something new!

Who said you stopped learning? Not this guy.

So I assumed when you were setting TDC on 'any cylinder' you would verify the position of the TDC mark on the starter ring. This would only work (as indicated) for the #1 or #2 cylinder on either compression or exhaust stroke. Either is fine for PMag timing.

I added a correction to my first post to avoid any confusion if someone researches this in the future.

Sorry for the confusion, but thanks for keeping me honest!

Dan
 
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