Ignition Systems

Early one September morning in 1908, Ernest Sweet, chief engineer for the Cadillac Motor Car Co., stepped off a train in Dayton, Ohio. He was met by an engineer who worked for National Cash Register.

In the five years he had spent at NCR, the younger man -- he was 32 -- had invented an electrically operated cash register that did away with hand cranking. He had also developed OK Charge Phone, the nation's first "automated" credit checking system. This magnetic device, placed in a cash register, allowed a sales person to press register keys and transmit information about a charge customer's purchase to a central office. Approval or disapproval was then telephoned back to the counter. The young man's contemporaries thought him a genius.

However, Sweet was not in Dayton to discuss cash registers. At the urging of his boss, Henry M. Leland, he was there to test-drive a Cadillac Roadster owned by the NCR engineer. Leland had received a letter from the Dayton resident describing a "flawless" battery ignition system for motor vehicles. Magneto ignition was the standard in those days because battery ignition just did not work. Sparkplugs fouled, vibrators failed, and batteries often gave out after 500 miles. Brief encounters with battery ignition by other carmakers -- Duryea in 1893, for example -- caused them to return to the reliable magneto.

For the next eight hours, Sweet drove the Cadillac over the hills surrounding Dayton, putting the Roadster through every rigorous test he knew. As the young engineer had promised, the ignition system performed flawlessly. As a result of this test, Leland met the NCR engineer several weeks later at Cadillac headquarters in Detroit to personally hand him a contract calling for 8,000 of his battery ignition units -- enough for every Cadillac that would be produced in 1910. The young engineer was Charles Franklin Kettering. In the years ahead, his influence on General Motors would rival even that of Leland.

What had Kettering done that allowed a battery ignition to perform reliably? To start with, he combined the standard four induction coils (one for each sparkplug) into one by placing them in a heat-resistant, solidly anchored, armoured-steel box and connecting them in series. This did away with the nagging problem of rapid coil failure caused by vibration and heat, and also allowed conservation of power. Battery life was therefore extended.

Kettering also eliminated the individual vibrators (also called "tremblers") - - one for each coil -- that made and broke the circuit. He replaced them with a single master set of contact points connected to a condenser. The condenser drew excess current away from the points, contributing to their longevity.

Tremblers (steel springs) were susceptible to loosening by vibration. This required motorists to make frequent adjustments. The devices also quickly burned themselves to death as a result of electrical arcing. Kettering's ignition produced a much hotter spark than ever before, using less battery current, which extended component life.

The contract Leland handed Kettering enabled him to quit NCR and begin his own business, which he called Dayton Engineering Laboratories Co. -- Delco for short. More important, the contract put Kettering's mind solely on perfecting what was to be the standard auto ignition system -- one that's still with us today -- and on development of the self-starter.

Yet, when the 1910 Cadillac Model 30 hit the showrooms, customers found that it possessed two independent ignition systems -- the much-heralded Delco and the standard magneto, installed just in case.

Although it was only another two years before dry cells were replaced by storage batteries, it was quite a while longer before storage batteries attained any degree of reliability.

As late as 1935, some manufacturers were still placing magnetos into cars. But, for all intents and purposes, the end of the magneto came with the end of the Model T Ford in 1927. Ford refused to trust battery ignition for the Model T, even after the development of more reliable storage batteries. So, every Model T came with a self-starter and battery for "modern starting," and a hand crank that sprung the magneto to life if the self-starter or battery failed.

Four basic systems - hot tube, magneto, battery and computerized

There have been only four basic auto ignition systems during the last 100 years -- hot tube, magneto, battery and computerized -- plus a number of oddball variations. As late as 1924, systems using lighter flints and moving files (sometimes attached to the piston) were being tried. Engines in which sliding valves exposed the fuel mixture to a pilot light had proved dangerous, and the hot tube finicky.

The hot tube was just that -- a closed metal tube that projected from the cylinder and was heated red hot by a sort of Bunsen burner. Because it was always hot, ignition took place as the compression rose -- there was no "timing" as such.

The advantage of a spark ignition is that, not only can you time it, but the flame doesn't blow out when you drive fast. The earliest sparks were produced by a tiny generator that employed permanent magnets and was therefore called a magneto.

Although several inventors are credited with developing magneto ignition, Siegfried Marcus was issued a patent in 1883 for a "magneto-electric ignition system." It proved to be the basis for an automotive ignition system that lasted until battery ignition took over.

Marcus's system used two contact points installed inside the cylinder: one was stationary, the other, movable. The stationary point was connected to the magneto, or generator. The movable point was mounted on a small plate. As the plate moved, it brought the two points into contact. At this moment, an external pushrod operated by the camshaft interfered to break the circuit and produce a spark.

The Marcus low-voltage make-and-break ignition system served well as long as motor cars were driven at low speeds by single-cylinder engines. But, as multicylinder engines became popular and roads improved, the need for an ignition system that could deliver a steady stream of sparks became apparent. The result was a jump-spark system that used induction coils, tremblers and sparkplugs.

Some of those plugs were ingeniously designed to compensate for fouling, which was frequent. They carried over to battery ignition systems.

One popular type had an insulated knob at the top that was connected to a small metal rod. It allowed the motorist to adjust a secondary gap, which could be viewed through a window in the plug's top section. Fiddling with this gap was said to blast away deposits.

Another type was a priming plug. The driver opened a small valve on the plug that allowed gas in a reservoir to drip through the plug itself and into the cylinder. There was, however, a problem: If the motorist didn't close the priming valves tightly before starting, the engine either flooded or, if ignition did take place, was transformed into a flame thrower. Then there was a plug with electrodes at both ends. If the motorist experienced plug failure, he simply unscrewed a terminal cap, turned the plug end for end, reattached the terminal cap was to the fouled end, and he had a fresh plug ready to go.

There have been many other ignition developments over the years -- spark advance components, for example. The first manual spark advance system was brought out by Packard in 1901. For years after, drivers controlled spark advance by a lever on the steering wheel hub. Studebaker pioneered the vacuum advance in 1930, and Chrysler installed the first combination vacuum and centrifugal advance unit in 1931. During the 1980s, on-board computers took over the job of spark advance. A computer can generate three-dimensional timing "maps," as opposed to the old, two-dimensional curves.

In l961, the Delco Division of General Motors announced an ignition system that eliminated contact points and condensers by using electronic circuitry. At the time, Herman Hartzell, Delco's chief engineer, said the new breakerless system was being studied with an eye toward installing it on trucks, tractors and heavy-duty stationary engines. Chrysler made a similar system standard equipment in 1972, and "pointless" ignition became universal.

Two years ago, a new computerized system reared its head-probably the most revolutionary development in ignition since 1908. Introduced by Buick driven off the external water pump. on its 3-liter V6 engines, it eliminates the mechanical distributor entirely. Sensors on the engine detect crankshaft angle and, therefore, piston position. This information is fed to the engine-control computer which, at the right moment, triggers one of three coils in a black box. Each coil fires two sparkplugs simultaneously, one near the end of a piston's compression stroke, igniting the air-fuel mixture, and the other near the end of the opposing piston's exhaust stroke, where it fires harmlessly. Each pair of plugs fires once for every crankshaft revolution.

Variations of GM's ignition are likely to show up on all gasoline engines of the future, replacing distributors just as the Delco breaker point system took over from the magneto.

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