Navistar MaxxForce 15, Руководство по обслуживанию

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ENGINE SYSTEMS 17
cylinder head. The intake manifold is an integral part
of the cylinder head casting.
If the EGR control valve is closed, only filtered intake
air flows through the ETV, mixing duct, and into the
intake manifold.
During cold weather, the Cold Start Fuel Igniter (CSFI)
rapidly heats the intake air by injecting and igniting
small quantities of fuel into the mixing duct.
After combustion, gases exit through the cylinder
head exhaust valves and ports.
The exhaust gas
is forced through the exhaust manifold where,
depending on the EGR valve assembly position,
is split between the EGR system and the exit
path through the high-pressure turbocharger and
low-pressure turbocharger.
The exhaust gases flow from the low-pressure
turbocharger through the vehicle aftertreatment
system to the exhaust tail pipe.
Air Management Components
Turbochargers
The MaxxForce® 15 engine is equipped with an
electronically controlled, pneumatically actuated two
stage turbocharging system. This system provides
high levels of charge air pressure to improve engine
performance and help reduce emissions. Because of
its ability to generate very high charge air pressure
levels, the system is fitted with an air control valve
to control over-boost and surging conditions.
The
air control valve is supplied compressed air from the
vehicle air supply tank. The compressed air flow to
the wastegate actuator is electronically controlled
by the air control valve based on the Pulse Width
Modulated (PWM) signal supplied by the Engine
Control Module (ECM). The high and low-pressure
turbochargers are installed as an assembly on the
exhaust manifold, on the right side of the engine.