But BMW's engineers think that they can regain this lost performance by redesigning the engine to have direct fuel injection and by turbocharging it.

What has turned the lowly four-banger into such a ready replacement for its bigger brethren is the widespread use of turbo-charging and direct fuel injection.

But most of the really detailed hard parts like carburetion, power transmission, fuel injection etc, are already solved and come in ready-made components.