A British company, Epicam, is developing a turbulence grid to help control the motion of the fuel/air mixture before it enters the engine.
The grid is mounted on the upper surface of the inlet valve, creating high-speed microturbulence in the mixture as it enters the combustion chamber. The grid's microturbulence has advantages over the eddies (turbulence) in current lean-burn engines. Large eddies can cause problems in initial ignition and later in the engine's cycle, when the ignited mixture can lose heat via a 'scrubbing' effect on the cylinder walls, or even extinguish itself.
A problem with the turbulence grid is that it can impede the airflow into the engine, which reduces the power, but with careful design this can be kept to minimum.