Mack ASET AC, Service Manual

Page: 94 / 536

DESCRIPTION AND OPERATION
Page 81
Internal Exhaust Gas Recirculation (IEGR)
A system whereby the exhaust gas is drawn from
the exhaust manifold back into the combustion
chamber during the intake stroke to control the
formation of nitrogen oxides (NOx). This is
accomplished with a special cam designed to
hold the exhaust partially open during the intake
stroke.
Exhaust Gas Recirculation (EGR)
A system whereby a pre-determined amount of
exhaust gas is reintroduced into the combustion
chambers. Adding a small percentage of the
noncombustible exhaust gases to the
combustible fuel and air mixture lowers the
overall combustion temperatures reducing the
formation of nitrogen oxides (NOx).
H-Ring
A type of guide ring used to prevent axial rotation
of the valve roller follower. On the E-Tech™
engine, a ring is press-fit into each valve lifter
bore.
Idler Gear
A timing gear positioned between the crankshaft
and camshaft gears in the front gear train of the
ASET™ engine.
Idler Tensioner
An automatic belt tensioning device designed to
maintain optimum tension under varying engine
speeds and load. The idler tensioner is optional
on the ASET™ engine.
Oxides of Nitrogen (NOx)
High temperatures and pressures of combustion
are what produce oxides of nitrogen (NOx). When
combustion temperature exceeds 2,500
°
F
(1370
°
C), oxygen and nitrogen combine in large
quantities to form NOx. By themselves, NOx
emissions are no great hazard; however, when
mixed with the right amounts of HC in the air,
NOx will combine in the presence of sunlight to
form smog. The ASET™ AC/AI engines use EGR
to cool the combustion process to lower
emissions of NOx.
Poly-V Belt
A multi-ribbed belt design which is incorporated
into the accessory drive belt and pulley
arrangement at the front of the engine. ASET™
AI/AMI (IEGR) engines use a single poly-V belt
and pulley arrangement; the ASET™ AC (CEGR)
engines use a dual drive belt and pulley
arrangement.
Rexroth Valve
See VTG Position Controller.
Roller Follower
A type of lifter with an axle-mounted roller that
rides on (or follows) a camshaft lobe. The rolling
motion of this design provides increased load
capacity with less friction than the flat-faced lifter
design. Roller followers are used to provide the
lifting action for the electronic unit pumps and the
intake and exhaust valves on the ASET™ engine.
Supply Pump with Integrated Fuel Filters
(SPIFF)
The fuel supply pump contains both a pre-pump
filter and a primary filter contained on one
integrated housing.
Tappet Guide Pin
A pin used to prevent axial rotation of an EUP
tappet. The pin is pressed into the cylinder block
EUP tappet bore wall and fits into a slot in the
tappet.
Variable Turbine Geometry (VTG)
Turbocharger
Turbo turbine housing has moving components to
control flow of exhaust gas and build
back-pressure in the exhaust system for EGR
flow.
VTG Position Controller
Mounted to rear of intake manifold, regulates air
pressure to control the VTG.
VTG Position Sensor
A sensor mounted on the VTG actuator that
determines the actuator’s true position.
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