I’ve been reading car reviews in anticipation of buying a new car. What does it mean when you say a car has an inline engine or a flat-four, etc. – Mary in Corner Brook, Nfld.
Those phrases refer to the arrangement of the cylinders in an engine.
There are generally two ways engineers do this – in-a-row (inline) or opposed. If all of the cylinders are in the same plane or line that is an inline engine. Most four-cylinder, all five-cylinder and some six-cylinder engines are laid out in this fashion.
Others with more cylinders used to be – that is why those old cars had those very long hoods to accommodate long engines that were referred to as “straight eights.” But, in the interest of shortening the engine and making it possible to fit it into a smaller space, engineers started to place the cylinders opposite each other in two rows that formed a “V”, always in pairs, because even numbers are necessary for balance.
The vast majority of these engines are in a “V” formation with three, four, five or six cylinders on each side. So they are called a V-6, V-8, V-10 or V-12 accordingly.
There are two types of “V” engines: one with a 60-degree angle between the two banks of cylinders and one with a 90-degree angle.
Some manufacturers have developed and still use engines with two banks of cylinders 180-degrees apart or opposed to each other. Subaru has done this with both four- and six-cylinder engines and Porsche with six. These engines are referred to as flat or horizontally opposed.
There have been other designs throughout the years including at least one horizontally-opposed 16-cylinder engine used in Formula One competition and Volkswagen engineers came up with a diabolically complex W-12 engine that is essentially two V-6 engines joined together with the inner bank of cylinders joined together so that, looked at from the end, it is a “W” rather than a “V.” All 12 cylinders share the same crankshaft, which is also the case for all the other designs mentioned above.
