Another fine wires vs conventional plugs question

[Andy95W]

On 5/12/2017 at 9:04 AM, cnoe said:

Those utilizing two separate mags would indeed experience accelerated electrode wear if not rotating in the traditional manner.
 

 

Cylinders 1&3 are fired by one magneto (whether top or bottom), 2&4 by the other magneto.

I run fine wires in the bottoms only.  Therefore, I rotate plugs 1->2->3->4->1 every annual/100 hours for top and bottom separately.

[Guest]

Spark plug rotation pattern.

 

[Andy95W]

Thanks Clarence. 

What are you supposed to do for an 8 cylinder, just put them all in a box and shake real hard?  

[Guest]

1 hour ago, Andy95W said:

Thanks Clarence. 

What are you supposed to do for an 8 cylinder, just put them all in a box and shake real hard?  

I'm the happy owner of 16 fine wires.  I advance them in the firing order, 600 hours and no appreciable wear.

Clarence

[jaylw314]

23 hours ago, Andy95W said:

Cylinders 1&3 are fired by one magneto (whether top or bottom), 2&4 by the other magneto.

I run fine wires in the bottoms only.  Therefore, I rotate plugs 1->2->3->4->1 every annual/100 hours for top and bottom separately.

IIRC, Lycomings IO-360's fire the 1&3 bottom and 2&4 top by the right magneto, and 1&3 top and 2&4 bottom by left magneto.  Since the firing order is 1-3-2-4, 1B has to be the opposite polarity of 4T, and 3B has to be the opposite polarity of 2T, hence the rotation sequence.

Rotating only bottoms or only tops would only work if you knew the two magnetos were firing the tops with opposite polarity.  I don't know if there's a way to make sure of that with separate mags (apparently they are fixed that way with the Bendix dual-mag), but I'm guessing there isn't, in which case you only have a 50:50 chance.

[cnoe]

I would like to clarify the technical error from my previous post. From the Champion Aviation Service Manual...

But the result is the same; dual-mag plugs don't require typical plug rotation.

Clarence had already posted the recommended rotation sequence above for two-mag engines.

[Andy95W]

20 hours ago, M20Doc said:

I'm the happy owner of 16 fine wires.  I advance them in the firing order, 600 hours and no appreciable wear.

Clarence

300 hours rotating 1->2->3->4->1 top and bottom separately and also no appreciable wear.

[Andy95W]

3 hours ago, jaylw314 said:

IIRC, Lycomings IO-360's fire the 1&3 bottom and 2&4 top by the right magneto, and 1&3 top and 2&4 bottom by left magneto.  Since the firing order is 1-3-2-4, 1B has to be the opposite polarity of 4T, and 3B has to be the opposite polarity of 2T, hence the rotation sequence.

Rotating only bottoms or only tops would only work if you knew the two magnetos were firing the tops with opposite polarity.  I don't know if there's a way to make sure of that with separate mags (apparently they are fixed that way with the Bendix dual-mag), but I'm guessing there isn't, in which case you only have a 50:50 chance.

So worst case scenario is that I'm reversing polarity every 2 years.

I'm okay with that.

Honestly, with all of the obvious concerns about flying single engine airplanes, rotating spark plugs is so far down the list of priorities it doesn't even make it onto my radar.