What type of combustion chamber was most commonly used in automotive applications during the 1990s?

The most commonly used type of combustion chamber in automotive applications during the 1990s was the indirect injection (IDI) combustion chamber. This design was prevalent in diesel engines, where fuel was injected indirectly into a pre-combustion chamber. This method allowed for more efficient combustion, higher power output, and lower emissions, making it suitable for the vehicles of that era.

During the 1990s, many diesel engines utilized IDI chambers because they offered advantages in terms of cold starting and noise reduction compared to direct injection methods. While direct injection technology began to gain traction later, particularly for its efficiency and performance benefits, the industry was still largely dominated by IDI designs at that time.

CI, or continuous injection, is less relevant in contemporary contexts, and although spark ignition (SI) combustion chambers are widely used for gasoline engines, they are not the specific focus in diesel applications, which were more prevalent in that decade. Thus, the selection of the IDI combustion chamber aligns accurately with the predominant technologies of the automotive landscape during the 1990s.