Venturi Inlet Restrictor

Venturi Inlet Restrictor Function:
Internal combustion engines are virtually air pumps, combining large amounts of air and fuel to produce power. And with any air pump, airflow is always the limiting factor. The use of a venturi inlet restrictor consistently limits airflow and therefore power. The Super Tuner Car Championship is mandating the use of an inlet restrictors in an effort to predictably and controllably create a competitive power to weight ratio. These restrictors are available from the series director. They have been optimized through computational fluid dynamics and designed to thrive in the harshest environments.

How a Venturi Inlet Restrictor limits power:
Commonly known as Choke flow, this is the limit when the restrictor has reached maximum air flow, regardless of downstream vacuum. This happens when the air moving through the venturi reaches the speed of sound. At this point, the amount of air traveling through the venturi is constant, and can not increase.

Performance with an Inlet Restrictor:
The reasoning behind using a venturi restricting is to limit engine power and maintain competitiveness. By limiting air flow, an inlet restrictor system will limit power. And on a properly tuned engine, a well-designed restrictor will not greatly affect power and torque below this limit.