Coil questions

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Model T Ford Forum: Forum 2010: Coil questions
Top of pagePrevious messageNext messageBottom of page Link to this message  By Dean Yoder on Friday, December 24, 2010 - 12:35 pm:

I have noticed Ford coil secondaries run 3.2K-3.5K

KW secondaries are lower resistance 2.1k--
Did KW use larger gauge wire?
Is the turn ratio the same?
Should you try to run coils of similar resistance for smother performance?
Does One give a hotter spark?
OK it's SNOWING sitting by the wood burner enjoying being warmed by the wood a second time.

Merry Christmas All & Have a safe Holidays.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Friday, December 24, 2010 - 05:56 pm:

Dean:

I have probably pulled out 2000 windings from both Ford and KW both early and later windings and in truth some KW windings are very high in resistance on the secondary with some measuring higher than 8000 ohms. It really doesn't matter much if at all. The higher the resistance of the secondary the more voltage loss but that assumes that the current through the secondary is large enough to measure any loss since Voltage drop is the product of Current flowing multiplied by the resistance and the spark current is very very small so the voltage drop in the windings is insignificant. Since the voltage generated is thousands of volts and the current flowing is in mA (thousandths of amps)then even a resistance difference of 5000 Ohms might only make a difference of voltage of 5-50 volts and at a total voltage of over 10,000 volts - the difference is just minuscule. In truth the lower resistance windings are probably just heavier wire and that means more physical strength to handle overheating or rough riding. For that reason I don't use the higher resistance windings of the KW later versions. As for hotter spark - assuming that the correct turns ratio is used and the coil is a fairly high Q coil then the amount of energy in the unit is determined by the strength of the magnetic field which is determined by the AMP-TURNS of the primary winding. The amount of amps flowing through the primary multiplied by the number of turns in the primary determines how hot the spark will be when the points open and all of the energy is then dumped by the secondary into your spark plug. I have omitted a lot of the details here but the basic question that you asked is answered. I cannot be certain that all coils sold by aftermarket companies have the correct turns ratio but one could reasonably assume that all KW and Ford coils made during the T era were made with correct turns ratio and yes turns ratio needs to be the same but the most important matching of coils it getting them all set to the exact same operate current so that the timing and energy is the same for all 4. To that end in truth then selecting coils with equal primary inductance would be more important than matching secondary resistance. An HCCT or equally accurate device is then the only real way to get them totally matched up by setting the current precisely but only when there is a single spark being generated so that the current setting is then accurate and the sparks generated are a single spark for each mag pulse.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dean Yoder on Friday, December 24, 2010 - 06:48 pm:

John,
Thanks fore taking time to answer my questions.
I was rebuilding some coils and wondered if I was crazy fore trying to keep the sets in similar parameters.
I do use HCCT.
Dean Yoder


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Danuser on Saturday, December 25, 2010 - 12:40 am:

Dean and John and your families, Merry Christmas and a Happy New Year, we snowplowed all day today and will tommorrow and Sunday, our family xmas is after the first of the year this year John and Karen Danuser


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Saturday, December 25, 2010 - 03:29 am:

Thanks John and the same from our house to yours.

Merry Christmas.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Martin Na. on Saturday, December 25, 2010 - 07:56 am:

Hi John
What do you mean (the coil is a fairly high Q coil)I have never heard that expression before.
I have owned Model T's since 1964 and repaired my
coils and bobbin plates.This is my first reply on
this modern contraption (the computer)and have really enjoyed the forum for information and fun.
Tees R Great.
Merry CHRISTMAS To All.
N


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson on Saturday, December 25, 2010 - 10:42 am:

Martin
John is probably entertaining his children and grandchildren this Christmas morning.
"Q" is the electrical symbol (just as "R" is the symbol for resistance) that refers to the Quality or Merit of the coil. To say this another way; Q is a formulaic combination of various electrical factors (Inductance, Resistance and Frequency) that determine how well this type coil performs.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerome R. Hoffman, Hays KS on Saturday, December 25, 2010 - 11:13 am:

Pretty soon my head is gonna explode from all this new information I learn every day. Just goes to show you no one person can know everything about the universal car. I just hope to know most everything........lol. Merry Christmas. Jerry


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