The spark that fired the automobile

Many of us have cursed them as we skinned our knuckles trying to extricate them from awkward parts of engines. But in 100 years, nobody has found another way of providing the key component of an internal combustion engine - the spark that ignites the fuel-air mixture.

On January 7, 2002, it will be exactly a hundred years since Bosch was awarded the patent for the first spark plug. Designed to be combined with a high-tension magneto ignition system, it solved what Carl Benz had described as the most fundamental obstacle to early motoring.

Together with improvements in production technology, it was the spark plug that laid the foundations for the rapid increase in automobile production over the decades that followed.

Nowadays, the spark plug, which has been developed and improved continuously over the decades, plays a key role in the clean and efficient combustion needed for reliability, fuel economy, and the operation of catalytic converters. Despite the tremendous increase in demands on the units, the service life of a spark plug is now about 12,000 to 18,000 miles, some 20 to 30 times further than the figure 90 years ago. Some special spark plugs even have a service life of 60,000 miles.

Even, in the last few years, Bosch has shown the potential still offered by this elderly product – adapting it for new developments in engine technology such as four-valve cylinder heads or lean mix engines. The latest example is the Volkswagen Lupo FSI, the first mass-produced car with a very low-consumption gasoline engine featuring both direct injection and stratified charging. Bosch not only supplies the entire injection and ignition system, but each Lupo FSI is fitted with Bosch spark plugs developed specially for this engine.

Design variants and special materials such as platinum and yttrium allow Bosch spark plugs to be used in a wide variety of applications.

Countless different types of spark plug can also be produced by changing the type, number and shape of the electrodes. The current Bosch spark plug catalogue includes 26 different electrode designs, each designed to help engines meet ever more stringent emission limits at the same time as ensuring greater efficiency and higher power output.

Decades of experience and a sustained development effort in close cooperation with virtually all the major vehicle producers have made Bosch one of the world's leading Original Equipment and aftermarket suppliers of spark plugs and the market leader in Europe.

All the leading car-makers fit Bosch spark plugs as standard equipment: Bosch customers include Audi, BMW, Cadillac, Citroën, Fiat, Daimler-Chrysler, Mitsubishi, Opel, Peugeot, Porsche, Renault, Seat, Skoda, Suzuki, Toyota, Volvo and VW. The range now includes more than 1,250 different models because many modern engines call for their own tailor-made spark plugs.

All in all, Bosch has developed more than 20,000 different types of spark plug over the past 100 years. In 1902, Bosch produced about 300 spark plugs. Now the company's plant in Bamberg alone produces about a million spark plugs every working day and world-wide production is about 350 million spark plugs per year.

Bosch also produces spark plugs at plants in India, Brazil, China and Russia for local markets and manufacturers. In total, Bosch has produced more than seven billion spark plugs. Laid end to end, they would stretch all the way to the moon.

A full range of advertisements for Bosch spark plugs down through the years is a trip through the history of the automobile, and can he seen here.