In exhaust gas recirculation a portion of the exhaust gas is recirculated to the cylinder
intake charge. This reduces the peak combustion temperature, since the inert gas serves as a heat sink. This also reduces the quantity of oxygen available for combustion.
The exhaust gas for recirculation is passed through the control valve for regulation
of the rate and inducted down to the intake port, The recycle rate control valve is connected to the throttle shaft by means of appropriated linkage and the amount of valve opening is regulated by throttle position. The link is designed so that recycled exhaust is normally shut off during idle to prevent rough engine operation. This is also shut off during full throttle, acceleration to prevent loss of power when maximum performance is needed.
The NOx concentration will vary with the amount of recycling of gas at various air
fuel ratios. About 15% recycle will reduce NOx emission by about 80%. The maximum percentage which can be circulated is limited by rough engine operation and loss of power.
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