Since the internal combustion engine has been invented, there have been developed lots of ways to arrange the cylinders, and the number of cylinders.
The most commonly used engine is the I4, which stands for inline 4 (4 cylinders). This engine is without a doubt, the most efficient in terms of costs, fuel consumption and reliability. That’s why most of manufacturers used it and still use it.
Before we get into more details, I would like to note down the other engine design layouts:
I3, I4, I5, and I6 – There are few manufacturers who don’t use Inline at all, manufacturers such as Porsche (they use V or H).
There are V6, V8, V10, V12 and V16 (Rolls Royce Phantom from Johnny English Reborn – 9.0L V16). Compared to an Inline engine, the V is more equilibrated, vibrations are significantly lower, larger power outputs can be implemented.
H shape (Boxer)
Porsche and Subaru use this engine layout. Subaru uses this layout for all its engine – both Diesel and Gasoline engines. There are H4 and H6 engines (H6 used by Porsche in their 2.7 and 3.4L gasoline engines).
This is basically an engine which has 2Vs with different angles. The main purpose of this engine is to reduce space for huge engines (6L and above). This kind of engines can be found in the Audi A8 6.3 W12 or in the Bugatti Veyron 8.0 W16.
Originally developed by Mazda and used only in the RX8, the Wenkel engine is a rotary motor which can reach 9,500 rpm. Power output is huge – 231 hp from a 1.3L engine, but reliability and fuel consumption are not great – the engine’s lifetime is around ~ 90,000 miles, and fuel consumption is around 20 MPG.