Why two small turbos instead of one big turbo?
Several reasons. First is that two smaller turbos spool much quicker than one large turbo due to the smaller size, yet still have the total airflow capacity of a larger single turbo. Second is this makes it possible to mount the turbos closer to the cylinder heads. This allows them to spool quicker also, reduces underhood temperatures (less exhaust tubing), less weight (less exhaust tubing again), and does not require you to modify your H-pipe. Single turbos require you to cut the H-pipe so that a Y-pipe from the turbo down pipe can be welded in place. If you have a stock H-pipe, you loose the front two catalytic converters. The car might not pass inspection as a result. Third reason is this is the only way that a CARB exemption # could be issued. All emissions equipment is unaffected. The single turbos require you to cut the H-pipe, and also the O2 sensors end up farther away from the cylinder heads. This is important during cold starts. O2 sensors require a certain amount of heat to
