Turbocharged petrol engines

Turbochargers are commonly used in passenger cars to obtain greater power output from a given engine size. The compact nature of a turbocharger means it is often a more space-efficient solution for increasing power output than increasing engine displacement. As an example, the turbo Porsche 944's acceleration performance was very similar to that of the larger-engine naturally aspirated Porsche 928. Although turbocharging is less responsive than supercharging, turbocharging is generally considered more efficient than supercharging. New techniques such as twin-turbo/biturbo (whether parallel or sequential) setups and twin-scroll turbocharger, in combination with technologies such as variable valve timing and direct fuel injection, have cut down on turbo lag.

Since 1978, many manufacturers have produced turbocharged cars.

Notably in the mid-2000s, BMW which long used small-displacement high-rev naturally aspirated engines, re-introduced its turbocharged gasoline engine, the BMW N54.

Some engines, such as V-type engines, utilize two identically sized, each fed by a separate set of exhaust streams from the engine. Having two smaller turbos produce the same aggregate amount of boost as a larger single turbo allows them to reach their optimal rpm, more quickly, thus improving boost delivery. Such an arrangement of turbos is typically referred to as a parallel twin-turbo system. The first production automobile with parallel twin turbochargers was the Maserati Biturbo of the early 1980s.

Another twin-turbo arrangement is "sequential", where one turbo is active across the entire rev range of the engine and the other activates at higher rpm. Below this rpm, both exhaust and air inlet of the secondary turbo are closed. Being individually smaller they have reduced lag and having the second turbo operating at a higher rpm range allows it to get to full rotational speed before it is required. Such combinations are referred to as a sequential twin-turbo. Cars using sequential twin-turbos include the Porsche 959, Mazda RX-7, Toyota Supra and Subaru Legacy. Sequential twin-turbos are usually much more complicated than a single or parallel twin-turbo systems because they require three sets of intake and waste gate pipes and valves to control the direction of the exhaust gases.

...
Wikipedia