GM Gasoline V6 90 Degree - Manual (Page 24)

ENGINE APPLICATION MANUAL GM Powertrain
Gasoline 4.3L V6 90 Degree Revised: 08/15/2000
File: c:\data\manuales\v6-truck\am43v6#3.doc
Contact:Luis Nespolo - (248) 857-1558 Printed: 8/15/00 22
3.1.6 Engine interface to exhaust
3.1.6.1 Content
The engine is provided with exhaust manifolds for vehicles and Industrial Applications.
The exhaust manifold system includes the manifold, fasteners to the cylinder head, and
partial or full cover type heat shield. The exhaust manifold may also incorporate provisions
for EGR attachment.
Vehicle Exhaust System
The 4.3L V6 90 Degree Engine shall be attached to the vehicle and interface with the
Vehicle Exhaust System.
The Vehicle Exhaust System will be designed or adapted considering the following Issues:
Vehicle Exhaust System Back pressure: All performance parameters specified in paragraph:
2.3.2.1 were measured with a maximum exhaust restriction of 8.5” of Hg.
Thermal Management of Exhaust
Thermal management of exhaust
The following issues must be considered:
a. Location of Catalytic Converter: The location of the catalytic converter is determined by
resolving three competing needs. The first need is to locate the converter such that it is
close enough to the engine so that sufficient heat is transferred to the converter via the
exhaust stream so as to initiate catalytic activity and therefore constituent conversion
soon enough to meet emission requirements. The second need is to locate the catalytic
converter far enough downstream from the engine in the vehicle’s exhaust system so that
the converter will not be damaged during extended duration high exhaust gas stream
temperature excursions resulting from high speed and load operation of the engine. The
third need is to locate the converter in a position in the chassis where it will package with
sufficient clearance to surrounding components or systems to prevent heat related
failures in those systems or components.
b. Location of Oxygen Sensor(s)
All OBD II compliant exhaust systems contain enough oxygen sensors to guarantee
proper monitoring of the exhaust gases. Each engine cylinder bank requires an oxygen
sensor for air/fuel ratio control. An oxygen sensor is required behind each catalytic
converter for diagnosis purposes. Post converter oxygen sensors are also implied for
slow air/fuel ratio trim. Oxygen sensor wiring connections must be located to as to avoid
moisture contamination.
c. Converter Volume and Flow
d. Location of muffler
e Vibration/shock of catalytic converter
f. Material life for exhaust system through catalytic converter
g. Thermal Characteristics
h. Exhaust Leakage
The exhaust system must be leak free for the emission useful life of the vehicle.
In order to have a working definition of leak free, the exhaust system is divided into three
zones:
Zone A (A/F Control) Cylinder head / exhaust manifold interface to
control oxygen sensor
Zone B (Converter Feedstream) Control oxygen sensor to converter
Zone C (Diagnostic Feedstream) Converter to 12 inches downstream of the
diagnostic oxygen sensor
Maximum allowable leakage in each zone is 2 liters/minute at 15 kPa.