L 1GZ-FE V12. The V series engines, like several Toyota Motor Corporation engines (e.g. 2T-C, 2M, 4M etc.) at the time had a hemispherical combustion chamber. The spark plugs were located at the top of the combustion chamber. Design evolution in modern engines In the modern emissions-era, the hemi chamber has begun to fade away from continuing development. The hemispherical combustion chamber is the simplest, and easiest design. It has served for more than a century as the basic design in combustion engines, from which many other improvements and engineering developments derive. As the engineering involved in new engines has improved and evolved, the true hemispherical chamber has morphed and twisted into more sophisticated and complex designs that are meant to extract more power, with lower emissions, from any given combustion event. Many of today's engines use active combustion chambers designed to tumble and swirl the fuel/air mix within the chamber for the most efficient combustion event possible. These active chambers usually look like kidney beans or two merged small 'hemi' areas surrounded by flat quenching areas over the pistons. References Piston engine combustion chambers Piston engine configurations