Last week I asked what was the first air-cooled racing engine, which had a large fan to force air across the cylinders? Hint: do not jump to the first conclusion! The correct answer was not Porsche, but it was a Frayer-Miller in 1906.
So to this week. In the early days of motoring, steam cars reigned supreme, but the invention of one accessory saw the internal combustion engine out-sell the steamers. What was it?