18
connectors between sensor and ECU. The breathability should be higher than 1 ml/minute at a test
pressure of 100mbar.
Underfloor installation of the sensor remote from the engine requires an additional check of the
following points:
-
Positioning of the sensor with respect to stone impact hazard.
-
Positioning and fixing of cable and connector with respect to mechanical damage, cable bending
stress and thermal stress.
The sensor cable must be routed so that it is free of bends, mechanical tension, and chafing points
considering the movement of the exhaust system in relation to the vehicle body. The cable and
connector should not be subjected to excessive temperatures that could cause damage.
Additional instructions for the installation downstream the catalytic converter
-
Between catalyst and sensor location absolute gas tightness of the exhaust system must be ensured.
-
When the sensor is installed in the exhaust pipe there should be no detachable connections
between catalytic converter and sensor (e.g. flange, clamp-screw joint).
-
In order to protect the active sensor ceramic against condensation water from the exhaust gas side
the sensor heater voltage must be power controlled after cold start of the engine. During the
condensation water phase, the ceramic temperature should be kept at approx. 302degF ~572degF
(150°C-300°C). The corresponding control parameter must be determined according to application.
-
The sensor should be mounted as close to the outlet of the catalytic converter as possible without
exceeding sensor maximum temperatures.
-
The sensor should be mounted as far from the exhaust pipe outlet as possible to avoid dilution from
ambient air. Minimum distance between sensor and exhaust outlet should be 15.7 inches (400 mm).
CATALYTIC CONVERTER
A very important component in a low emission engine is the catalytic converter. Weichai engines use a
TWC converter. For this type of catalytic converter to work properly, the following two criterion must be
met:
-
The air-to-fuel ratio must oscillate between rich and lean.
-
The catalyst substrate (also known as a “brick,” located inside the converter shell) must be kept hot.
Strict compliance with these provisions, conditions, and operating limits for catalytic converters must be
maintained. If these parameters cannot be met or are not known, additional engineering and validation
are required.
Operation
-
The continuous operating exhaust gas temperature must be between 1112degF (600°C) and
1562degF (850°C).
-
The product installer shall take necessary precautions to accommodate shell skin temperatures up
to 1202degF (650°C).
-
System backpressure must remain with +/- 5% of nominal conditions.
-
Engine misfires and exhaust stream containments are not permissible.
WEICHAI & PSI SERVICE MANUALS AVAILABLE ONLINE AT FLYPARTSGUY.COM
GET YOUR WEICHAI & AFTERMARKET SERVICE PARTS AT FLYPARTSGUY.COM
