Cub ground

Though due to the edison effect ( thermionic emmission ).. pos grnd should help with spark plug life..

Soundguy

John T (long retired EE so a tad on the rusty side lol)

And the coil, since they are a dc induction coil, and the secondary is tied to one of the primary sides of the coil.. hooking it up in it's correct orientation makes a difference in how much copepr the electrons have to fire thru.. Hooking up 'backwards' adds the primary winding tot the path... no biggie.. still works.. but can reduce spark intensity parasitically

Soundguy

Let me toss out an idea to get your opinion !!

Do you agree ????? ?

IFFFFF F the coil is wired in the correct polarity, doesnt the secondary electron flow then take place FROM the hotter electrode tip TO the cooler ground strap BUTTTTT if its wired in reverse,,,,, thennnnn the electron flow is in the less efficient direction FROM the cooler strap TO the hotter electrode tip anddddd dddd thats a reason why the spark has more energy (volts x amps x time energy discharge across the gap) if the coil is wired correct!!!!! I think the figure I read or heard was that the coil voltage has to raise like 4k volts higher to arc current across the gap if wired in reverse then if wired correct. I.E. DOES the secondary arcing current flow in the opposite direction across the plugs gap if the coil is wired in reverse???? Im pretty sure it does and to tell one could place a lead pencil tip in say a 1/4 inch gap between the plug wire end and the plug and actually physically observe the direction the lil carbon sparks move, TO OR AWAY from the plug. Im fairly certain ifffff the coils wired correct the electrons which have a mass are gonna cause lil carbon sparks to move towards the plug iFFFFF F the coil is wired correct but in the opposite direction if its wired reverse.

Sooooo what ya think?? Agree???

John T (been the late sixties since I studied this at Purdue in EE so Im a tad rusty lol)

Now.. that said.. If you have a positive ground tractor, the spark is going to jump from the negative electrode tip, to the positive strap. That's where part of the efficiency comes in.

Now.. as for the wireing the coil incorrectly.. that is.. reverse the polarity of the charge system... ( charge system is still positive ground, but the coil is hooked up backwards ).. here is the condition... The secondary coil is hooked up in 2 places. 1 place is the high tension lead out to the spark plug wire/distrib cap... the other lead is hooked to one side of the primary.. Ideally, for correct phasing, it will be hooked to the side of the primary that is common with the incoming power/primary wire... However.. if yuo have the coil backwards.. you actually have the secondary connected to the outgoing side of the primary coil.. thus, spark current must pass thru the primary coil as well. Even though it is only DC 1+ ohms or so in the primary.. you have to look at impeadance since it isn't a steady state circuit, and you have to look at inductance of the primary.. etc.

As was stated... the coil works both ways.. it is just more efficient to use it in the correct polarity.

The spark is going to jump from negative to positive.. so, battery ground polarity will determine if the arc jumps from the tip to the strap, or from the stap to the tip. So.. it's really a 2-part issue... ground polarity controlling direction of spark jump, and coil orientation controlling spark intensity... etc.

Spark gap size, and compression ratio will determina at what high voltage level the discharge occours at. Close gaps and low compression make for an easy gap to jump... thus lower KV needed to jump.... wide gaps and higher compression make for harder gap to jump.. thus the voltage builds up to a higher potential before arcing.

To illustrate this, a spark plug, help in the open air may produce a nice blue spark.. but in the engine with a 6:1 compression ratio.. that may actually be an orange spark, if the coil is alread discharging at full potential.

In the old days, they made a product called a spark intensifier.. it was noting more than an inline adjustable spark gap that added a little gap.. thus letting high voltage build up to a higher potential before jumping. Similarly.. they made a device that will let a fouled plug fire.. uses same principal. I've seen farmers that had a foule dplug that was missing, pull the spark plug boot off and leave the metal contact about 3/16 an inch away from the spark plug tip so that it would arc over, and that cylinder would then start fireing.. due to the increased potential being able to jump the fouled gap..

Some engine anylizers will provide kv info, and you can also get KV reading volt meters, and even cheaper ones that are used to measure electric fences... etc.

Soundguy

The old farmners trick of the extra gap in the plug wire circuit has kept many a tractor running that would otherwise not fire on that cylinder and I think Champion makes a plug with the "U" or "UD" designation that has its own built in extra air gap. Of course, theres no free lunch and we cant create or destroy energy just change its form and looks like we all agree the coil is more efficient for sure if wired correct. The losses would be to heat when we would prefer it be discharged across the plugs gap to ignite the fuel.

Ill let ya all know if I run that experiment sometime, take care now

John T

Soundguy