In the early 1920s, four-cylinder engines were all the rage. With an increasing demand for cars, however, came the need for more cylinders
Matt Burt
1 October 2015

The 1920s were dominated by in-line four-cylinder engines, from the compact Wolseley-derived 847cc unit in the Morris Minor (pictured above) to the 4398cc Bentley, the largest engine on the market at the time.

However, the end of 1928 marked a notable shift towards a higher number of cylinders, with Autocar going so far as to write: “It is probable that in very few other years has there been quite so much upheaval. The four-cylinder engine is decreasing in popularity for cars exceeding a certain price and over a certain engine capacity.”

The increasing demand for powerplants with six or in some cases even eight cylinders was more than just a fad. Autocar reported: “The four-cylinder, when it came in many years ago, was almost universally adopted because it was more flexible and smoother than the single or two-cylinder engines which up to that time had been the limit of daring in design.

“Now, the four-cylinder is being superseded by the six simply because for an engine of a given size, six small impulses in a given time afford a smoother propulsive effort than four, and approach nearer to the ideal in which the engine would develop a continuous effort the whole time the crankshaft is revolving.

“The same is true of the straight eight, and still more so of the twelve-cylinder engine; the greater the number of cylinders, the more the explosions of individual cylinders overlap and the less it is apparent that the power unit is an explosive motor.”

Fuel economy was also an important factor. “A small six-cylinder engine can be used in place of a much larger four-cylinder without reducing, to any appreciable degree, the range of performance obtainable from the car. This, in turn, means a lower top gear; though it lessens the maximum speed possible with the car in question, it greatly increases the possible range without the need for a gear change.”

At the time, hillclimbing was regarded as a great test of a car’s abilities. Autocar reported: “A car climbs hills better on a given gear ratio with a six, eight or twelve-cylinder engine than it does with a two-cylinder or a four, and climbing hills without changing gear is a most important point in the average man’s view, provided that the act of changing speed needs any skill.”

Looking beyond 1929, Autocar was minded to make a bold prediction: “Without doubt, cars will have still more cylinders in the future and it may be that a 1.5-litre machine will be built having a power unit with 16 tiny cylinders giving, for all practical purposes, a continuous turning movement to the crankshaft or crankshafts.”

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Comments
6

1 October 2015
No emission regulations a decade ago and fuel consumption was not so important. If you could afford the car, then you could probably afford the petrol to run it. Cars were more toys for the rich, rather than transport for the people, with new cars costing several times the average person's annual income. Interesting how we've come a full circle with the current trend towards small three cylinder and in some cases two cylinder engines.

1 October 2015
Might be slightly more than a decade ago, @LP. Aren't we lucky these days, not to have to go up steep hills in reverse because first was not low enough! e.g. Ford Model T.

1 October 2015
Err, yes, of course I meant a century ago!

1 October 2015
It did happen too.. BRM introduced one only 20 years later (1948). Shame that design didn't become widespread though!

1 October 2015
Why Sep 28 1928? What happened on that date? It wasn't even a Friday. Hispano-Suiza had been producing straight sixes since 1919 and Cadillac's first V8 was 1915. One other advantage of more cylinders per engine size is lower piston speeds at same revs, unless you are silly with the bore/stroke ratio.

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