Capacitive Discharge Ignition (CDI) theory is credited to Nikola Tesla (the same person the car is named after). In 1897 Mr. Tesla applied for this patent:
Historically, Robert Bosch is credited with the first working example of the CDI built for fighter aircraft during WW2:
More on the history of CDI:
My interest in CDI history occurred when I sent the patent information for the Huff magneto (used on the Ford Model K) to an automotive electronics authority. After reviewing the patent and related journal descriptions of the Huff magneto, this auto electronics expert responded back that the Huff magneto and corresponding ignition system was actually a Capacitive Discharge Ignition.
According to him, the system, used on the Ford Model K, uses the same methods as a modern CDI, with the magneto armature developing electrical current that charges the condenser. Then, through the magneto timer, acting as a distributor (hope I'm writing this correctly) the condenser sends this high voltage charge to the coil, and an extremely high voltage charge is sent on to the spark plug, resulting in a brief, high voltage spark. Advantages of this system include less plug fouling and more reliable spark at high rpm.
Yesterday during the New London to New Brighton tour we had our first chance to try the system (the magneto was just rebuilt). Dean Yoder wired the mag to the condenser, and on to a Model T coil. I used a small cordless drill at a few hundred rpm to turn the magneto. The resulting spark jumped a gap about two inches wide, sometimes sparking across a gap as wide as three inches and sometimes jumping directly between the coil contacts.
The spark can be seen between the wire to the left of the top coil contact, arcing to the contact
This link shows the system working in a short youtube video:
It appears, according to several people who know much more about automotive electronic systems than I, Ford may have had the first working CDI system. Furthermore, the Ford Model K may very well be the first production automobile to use CDI as it's primary ignition system.
It seems that before Henry Ford and Ed Huff developed the Model T magneto, they collaborated on what may be the first working CDI system, that is still being used today. With Dean's help, we hope to have the system back on the car and operational soon (currently we are using a Bosch DU-6 mag on the car).
I agree, it does look like the same circuitry as that used in the typical hot rod shop CDI from the 1960's, although the Model K uses a timer to complete the 75 volt low tension circuit instead of the points in a distributor for the 1960's version.
Don Mates writes about it in this article from the Horseless Carriage Gazette several years ago, noting that with original Model K spark plug wires it has problems with cross firing. Don recommended using a high quality set of modern plug wires to combat the problem:
" although the Model K uses a timer to complete the 75 volt low tension circuit instead of the points in a distributor for the 1960's version."
No, the distributor is in the magneto. The Model K has two entirely separate ignition systems, the "CDI/Magneto" and the NRS style battery/coils/timer. This system was also used on the six cylinder racer.
I suspect the 70 plus year old wiring (at the time Don wrote about the Model K) may have something to do with the arcing that he experienced on his Model K Roadster.
Another difference from a true Capacitive Discharge ignition is the low tension Model K magneto supplying power. The 1960's CD ignition uses battery power, and a power transistor amplifier circuit to step up the voltage to the capacitor / coil. In the case of the CD system used on the 1964 Thunderbird Ford called it "transistorized ignition" because the system would not have been possible without the then new technology of the Texas Instruments power transistor.
The Model K system uses similar thinking but a completely different source of power on the low voltage side of the circuit.
"true Capacitive Discharge..." ??
Hogwash! The T uses two different sources of ignition power, and you don't trivialize that.
BTW, I bought a 1964 Tbird with 50K miles, put another 100K on it, and didn't have any ignition trouble. Motorola, not TI, was first with the TO-3 power transistor. I worked with them in 1958.
Transistorized capacitive discharge was an option on the '64 Thunderbird. It still used points to trigger the spark event.
In March 1954 TI was ready to make two exceptional advances: the production of the silicon grown junction transistor and a germanium diffused grown junction device for the first transistor radio.
TI made its first transistors in August 1952 and went public on its Types 100 and 101 in March 1953. A year later these transistors were redundant and replaced with hermetically sealed versions. The range was relatively comprehensive with dedicated grown junction types for hearing aids representing the main outlet. The first silicon product was available: the 600 series silicon junction diodes.
In 1954 TI made:
Type 102 and 103 hermetically sealed point-contact transistors from September 1953
Type 200 series NPN grown junction transistors for hearing aids and general purpose applications
Type 300 series PNP alloy junction transistors
Type 600 and 601 silicon junction diodes
Type 700 tetrode for AGC applications
Type 800 photo transistor
X-2 experimental NPN grown junction small power transistor
Back in the early '50s I saw an article in some magazine and thought "that'l be kool",
Built one and put it in a '46 or'47 GMC pickup. It worked pretty good, but the T V was blocked out for about a half a block while I was driving.
Neighbors convinced me to remove it from the truck.
The Holley-Huff magneto generates over 200 volts, not 75. Below is a 1906 A.L.A.M. journal interview with Ed Huff and George Holley discussing the differences between this magneto and high or low tension mags. It's a detailed description and quite interesting that Ford used this concept on a production car in 1906, years before automotive historians say a working CDI system existed:
Can't wait for you to get this mag working on your K, Rob. It will be good to see how often it starts on the switch.
I'm looking forward to trying it. Ford claimed a significant power and speed increase when switching to magneto, it will be interesting to see. Early carburetors seem to be notorious for running rich and fouling plugs. This system may have been a good option to avoid fouled plugs and the resulting engine misses.
Currently, when we switch from mag to battery (I usually run both) there is no noticeable power increase on mag (Bosch DU-6). Below is another video. At the end, I turn the mag by hand simulating cranking, and there is still a strong spark generated with about a 3/8 inch gap:
We've learned the Model K had four different ignition combinations. On the battery/timer side, just as with the NRS models, there is a "battery 1" and "battery 2" side.
On the magneto switch, one choice is magneto (CDI system). The other switch position connects the battery to the magneto distributor to a single coil, duplicating a "modern" distributor system. The literature says one may start on battery (not the timer system, but through the mag distributor) and then switch to magneto (CDI). Two sets of plugs per cylinder allow dual ignition with the combinations listed above as choices.
In 1906, no other domestic car maker offered a magneto as standard equipment except Ford on cars costing less than $4500.
Did you verify that the magneto is firing the correct sparkplugs? I questioned that some time ago.
I have gapped the plugs a little narrower as per Bosch DU instructions I found online. I'm not aware of any other plugs that are recommended?
The K runs quite well on on coils, and I'm not concerned that the mag does not make it run better. I have noticed the car is more responsive to the spark setting on coils compared with mag (I believe that's to be expected). I'll try to find the article where Ford claims the car will run noticeably better on the Holley-Huff.
I meant the placement of the sparkplugs in the head, Rob. The plug closest to the intake valve is going to fire easier, because it has a mostly fresh charge to ignite. The plug farther away is going to get a leaner mix, with hot exhaust gas.
That is the problem with the Lizard head, for example, as Charlie put the plug over the piston instead of near the intake.
Whether you want the buzz coils or the mag to fire the prime plugs is worth considering, and no doubt tested by Henry. Do you have any Ford docs showing the wire routing?
I have better than that (wiring diagram). Ford specified in the Model K owners manual which way to place them. I just didn't know why, until now. One learns something new everyday!
Model K manual reference ignition systems:
This 1906 article of the Model K gives an in depth review of the "new" model Ford. The article says the Ford will pick up speed when the magneto is switched on "and run at least ten miles an hour faster."
The entire article is linked below. In addition to the ignition system, the article discusses why a two speed and that initially 500 K were to be manufactured. The article also credits Ford with building more six cylinder cars than any other manufacturer (other six cylinder manufacturers in 1906 included Franklin, Stevens Duryea, Frayer-Miller, Napier and Rolls Royce):
Excerpt on magneto information:
Good info, Rob. From what I saw last year, I believed your magneto was connected to the plugs farthest from the intake valves, which is why I questioned it.
Yes, they were. I switched them to the "intake" plug but had no idea why (one of the few times I followed the directions ).
Thank you again for explaining why Ford placed hem there,
There's a better explanation in some of the era books.
Someone needs to ask - If the system was great, why was it only used on the Model K, then discontinued?
Good question. My suspicion is it was too expensive to carry over to the Model T (Ford already held the patent rights) and too much maintenance was required. As mentioned earlier, leaking and arcing might be a problem with high voltage and period insulation (just my guesses).
Interestingly, Holley still lists a six cylinder car (Model K) winning the 24 hour race as a factor in their early success, although Ford Model K is not specifically mentioned.
Holley online performance products description:
The Holley Foundation:
And this is how Holley took advantage of the Ford Model K 24 Hour Record in July 1907, advertising their magneto: