MLU FORUM - How To: Spark plug polarity

MLU FORUM (http://www.mapleleafup.net/forums/index.php)

- The Restoration Forum (http://www.mapleleafup.net/forums/forumdisplay.php?f=17)

- - How To: Spark plug polarity (http://www.mapleleafup.net/forums/showthread.php?t=28136)

Spark plug polarity

This concerns restorations. We do need to have the spark plugs polarity correct, on any vehicle. Even a blitz.

http://mgaguru.com/mgtech/ignition/ig104.htm

The main web page has much useful info

Mike,

The article is actually about ignition coil polarity. I found it while searching for solutions to solve the ignition troubles on my F15A. I did change the ignition coil polarity as the Ford has a positive chassis ground, and it was one of the parts in the puzzle improving ignition (along with new wiring, spark plugs, condensor and points).

Hanno

Quote:

As one end of the primary winding in the ignition coil is connected to one end of the secondary winding, reversing polarity of the coil primary side will reverse the drive direction of the spark current on the output side (even though current in the vehicle low voltage wiring still flows the same way). So reversing vehicle electrical system polarity will reverse direction of spark drive.

*snip*

End result is a difference of 15 to 30 percent in voltage required to make spark "initially" jump the gap on the plug depending on which way it is going. So the spark plug prefers to see a voltage potential that is negative on the center electrode and positive on the end electrode for the very first hop of the spark.

Hanno, I have read that once a coil has been used the wrong way it gets used to it and when you change it over, its ouput can be significantly reduced.

Quote:

Originally Posted by Lynn Eades (Post 244471)

Hanno, I have read that once a coil has been used the wrong way it gets used to it and when you change it over, its ouput can be significantly reduced.

I think that would be true if the coil has a iron core , the core will retain a little residual magnetism . But if you change the wires around to the correct polarity , the reversal of polarity will quickly re-energise the iron core to the correct polarity . In theory the output will not be reduced.

If you reverse the polarity of a auto generator, it's power output is not affected

My Land Rover has a + ground system . The coil has the terminals marked: CB (contact breaker) and IG ( ignition) only a blind person would connect the wires the wrong way around.