http://ca.autos.yahoo.com/011121/11/ekk4.htmlThere are several ways Subaru has reduced emissions on this engine. Some of them help economy as well. The most unique is their "Tumble Generator Valve". These valves look like extra throttle plates for each cylinder, but they are located directly above the fuel injector. At temperaturesbelow 60 degrees C, the computer closes the valves, forcing all the intake air to flow through a small idle air passage directly past the end of the injector. This high velocity, swirling air mixes with the fuel to provide excellent fuel delivery to the cylinders. The system works so well, that the engine can run at a stoichiometric 14.7:1 air fuel ratio as soon as the engine has started. Normally engines must run on the rich side during a cold start, but not this Subaru. After the engine has warmed up, the valve opens allowing full airflow to the engine.