Carbureted Engine

Fig. 49 Typical throttle control dash pot system.:

The dash pot system, Fig. 49, slows the closing of the throttle. When the engine is running, ported vacuum is applied to the throttle opener through the dash pot check valve. On deceleration, the vacuum bleeds off through the fixed orifice in the dash pot check valve, gradually decreasing the vacuum until the throttle closes completely. The speed at which the throttle closes is determined by the size of the fixed orifice in the dash pot check valve, the tension in the throttle return spring and the amount of vacuum generated at the carburetor port.