 This means that total engine airflow would not increase by the amount suggested by these figures, which apply only to the entry alone, as the inlet end is never the smallest or most restrictive part of the system.Because the greatest losses to flow occur near the valve seat, actual overall gain from any improvement of the entry flow would be much less.In the real world, on high-rpm IR IC engine, using a minimum amount of inlet radius gives the best wave strength and a power boost of 2% to 4% over a 3000 to 3500 rpm range.