Spark Plug ( 1902 ) | Honold paves the way for engines with higher operating speeds

"The high-voltage magneto and spark plug...became available just as serial car production [ took off ]." Vaclav Smil, Creating the Twentieth Century

 Gottlob Honold's ( 1876-1923 ) career as an engineer and inventor started with a lucky break. His father was friends with the father of Robert Bosch, founder of the great German technology company. At the age of fourteen, Honold was given his first job in Bosch's workshop in Stuttgart, where he began to hone his technical prowess. He later left to study engineering at Stuttgart University, but returned to Bosch in 1901 as their technical manager. It was then that he made important changes to the concept of the spark plug.

Spark plugs were made earlier, but only Honold's magneto-based ignition system was practical.

Ignition systems for cars had been around for some time, but none of them were reliable. Some systems rapidly drained the car's battery, whereas the Daimler glow tube ignition system sometimes even set fire to engines. The issue of inventing a reliable ignition system for cars was described as the "problem of all problems" by automotive pioneer Karl Benz.

Honold developed a high-voltage magneto ignition unit complete with a spark plug. Previously, magneto ignition units had only been used on stationary engines but when Bosch fitted one to a motor tricycle in 1897, it was able to reach speeds of up to 50 mph ( 80kph )-extremely high for the time.

Honold's souped-up version, in which the electric charge for the spark plug is generated by the movement of magnets within the engine itself, allowed the development of engines with higher operating speeds of around 1,000 rpm. It coincided with the increase in demand for cars and Honold's design soon became standard. In 1902 Bosch made some 300 spark plugs; a century later worldwide production had reached more than 350 million.