Pulse Air Aspiration System

Fig. 6 Aspirator valve:

The valve, Fig. 6, in this system uses exhaust pressure pulsations to draw air into the exhaust system to reduce CO and HC emissions. It draws fresh air from the ``clean'' side of the air cleaner and past a one-way spring loaded diaphragm. The diaphragm opens to permit fresh air to mix with the exhaust gases during negative pressure (vacuum) pulses. When the pressure is positive, the diaphragm closes and no exhaust gases are allowed to flow past the valve. The aspirator valve works most efficiently at idle and slightly above idle when the negative pulses are maximum. At higher engine speeds, the aspirator valve remains closed.