Mode Of Operation Of The Secondary Air System Sas (Starting With The 2004 Model) - KTM 400-660 LC4 1998-2005 Repair Manual

2-11E

Mode of operation of the secondary air system SAS (starting with the 2004 model)

1
Hot exhaust gases flow through the exhaust port . The flow conditions in the exhaust port and the entire exhaust system's
influence on the escaping gas lead to a brief pressure drop in the exhaust port (vacuum).
2
The secondary air valve (SAS) opens during these cyclic vacuum stages, supplying oxygen to the hot exhaust gas through the
line 3 .
The secondary air valve prevents exhaust gas blowback into the environment.
2
In an overrun condition (extreme vacuum in the intake port)the SAS valve will interrupt the air supply to the exhaust port to
prevent any exhaust backfire.
4 5
The control valve is regulated by a control line . The control line transfers the vacuum from the intake port to the control
valve.
The control valve is open in the lower part-load operation (slight vacuum in the intake port).
The reaction between the atmospheric oxygen and the toxic constituents of the exhaust gas (CO - carbon monoxide and
HC - hydrocarbon) leads to a significant reduction of pollutants through the afterburning of CO and HC and a dilution of the
exhaust gas.
NOTE: The secondary air system does not influence the engine performance.
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