Variable Tumble Control System (MAZDA6 (2.3L) & MIATA)
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The shutter valve in the intake manifold lower runners closes at low RPM to improve emissions and fuel economy on California models. When the valve is closed, air flows through upper runner of intake and tumbles in the combustion chamber. The valve opens during high speed operation to allow full airflow through both runners and improves high RPM performance. The Variable Tumble Control System (VTCS) includes a shutter valve, shutter valve actuator, delay valve, solenoid, vacuum chamber and check valve.