The Ford Barn

30 Closed Cab PU · 08-14-2020, 01:48 PM

Am starting a new string on an old subject. Performance of the Pertronix Coil. This has been a subject for a long time, with Purdy leading the charge (pun intended). I have been thinking about it again due to this string. https://www.fordbarn.com/forum/showthread.php?t=285559 starting with post 16

Since starting the hobby in 2011 and knowing nothing about the A, have been led astray many times, especially in the beginning. And sometimes causing me a lot of grief/wasted time. Mostly because I was not aware of the Model A forums and was not a member of a Club. So I tend to be very skeptical of things I do not understand, and typically do not blindly accept what I am told.

I have always believed Purdy's claims, but have remained skeptical since I could not grasp how this coil is an improvement. I think I've had an "Aha" moment . So would like Purdy's and others opinions of what I think I know.

A Spark happens when voltage across a gap reaches the air impedance to jump the gaps and ionizes whats between the air gaps (in an A rotor and Spark plug gaps). Once the air ionizes it reduces the impedance in the gap to almost 0, and the Spark continues until the energy across the gap is depleted.

So in the case of the Pertronix, as long as there is enough points closed time so it can reach full capacity, it stores more energy than a standard coil. Then across a close to short when the air is ionized it can supply more current in the spark, which creates a more intense higher energy spark. The limiting factors for current/hotter intensity are - the coil wire impedance , the cap button to rotor connection impedance, and Pertronix secondary impedance and other design considerations. Spark plug leads are solid straps, impedance is 0.

A possible down side to this is an increase wear on the gaps components due to the higher current sparking.

A thing I missed previously is Purdy has increased the gaps. I'm not sure what this does for the quality of the Spark. Possibly Increasing the gap increases the time the coil has to store energy, so insures the coil takes a full charge in its coils? If too much, would the coil heat up?

Sorry for being so long/wordy, trying to be thorough.

So, comments?

08-14-2020, 01:48 PM	#1
30 Closed Cab PU Senior Member Join Date: Aug 2018 Posts: 2,332	Pertonix Coil Performance Am starting a new string on an old subject. Performance of the Pertronix Coil. This has been a subject for a long time, with Purdy leading the charge (pun intended). I have been thinking about it again due to this string. https://www.fordbarn.com/forum/showthread.php?t=285559 starting with post 16 Since starting the hobby in 2011 and knowing nothing about the A, have been led astray many times, especially in the beginning. And sometimes causing me a lot of grief/wasted time. Mostly because I was not aware of the Model A forums and was not a member of a Club. So I tend to be very skeptical of things I do not understand, and typically do not blindly accept what I am told. I have always believed Purdy's claims, but have remained skeptical since I could not grasp how this coil is an improvement. I think I've had an "Aha" moment . So would like Purdy's and others opinions of what I think I know. A Spark happens when voltage across a gap reaches the air impedance to jump the gaps and ionizes whats between the air gaps (in an A rotor and Spark plug gaps). Once the air ionizes it reduces the impedance in the gap to almost 0, and the Spark continues until the energy across the gap is depleted. So in the case of the Pertronix, as long as there is enough points closed time so it can reach full capacity, it stores more energy than a standard coil. Then across a close to short when the air is ionized it can supply more current in the spark, which creates a more intense higher energy spark. The limiting factors for current/hotter intensity are - the coil wire impedance , the cap button to rotor connection impedance, and Pertronix secondary impedance and other design considerations. Spark plug leads are solid straps, impedance is 0. A possible down side to this is an increase wear on the gaps components due to the higher current sparking. A thing I missed previously is Purdy has increased the gaps. I'm not sure what this does for the quality of the Spark. Possibly Increasing the gap increases the time the coil has to store energy, so insures the coil takes a full charge in its coils? If too much, would the coil heat up? Sorry for being so long/wordy, trying to be thorough. So, comments?