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LT4 Supercharger Description and Operation
Intake Manifold/Supercharger Assembly
The LT4 Roots-type supercharger is a positive displacement pump that consists of 2 counter-rotating rotors installed into the
lower intake manifold housing. The rotors are designed with 4 lobes and a helical twist. The rotors of the supercharger are
designed to run at a minimal clearance, not in contact with each other or the housing and are timed to each other by a pair of
precision spur gears which are pressed onto the rotor shafts. The rotors are supported at each end by self-lubricating non-
serviceable bearings. The drive belt pulley is pressed onto the input shaft. The input shaft is coupled to the rotor shaft. Both
the belt pulley and shaft coupling are also non-serviceable.
The upper intake manifold housing has an integrated intercooler. Cooling the air enhances the effectiveness of the
supercharger. The intercooler uses conventional coolant in a system that is separate from the engine cooling system. The
intercooler system includes two charge air coolers/heat exchangers, a water manifold assembly, and a variety of sensors to
monitor air temperature and pressure. The water manifold, located at the front of cover transfers coolant to the cover via four
internal transfer tubes. The transfer tubes and water manifold are sealed with O-rings and press-in-place seals. Coolant enters
the inlet port of the water manifold assembly, is directed into and through the two charge air coolers/heat exchangers, and
exits back into the water manifold. Coolant then exits the water manifold outlet port returning to the separate cooling system.
The two charge air coolers/heat exchangers are not serviceable.
Supercharger operation
The supercharger is designed to increase the air pressure and density in the intake manifold. When this air is mixed with
the correct amount of fuel the result is more power from the engine. This excess air creates a boost pressure in the intake
manifold with a maximum engine boost of 66.9 kPa (9.7 psi). Because the supercharger is a positive displacement pump and
is directly driven from the engine drive belt system, boost pressure is available at all driving conditions.
The over boost control solenoid is an electrically operated vacuum solenoid valve that is attached to the supercharger housing.
The three-way valve is controlled by the engine control module (ECM). The ECM determines when pressure in the manifold
exceeds the desired operating pressure and directs manifold pressure to the bypass actuator. Manifold pressure in the
actuator opens the bypass valve and lowers boost pressure.
The bypass actuator is a vacuum operated valve that is connected to the vacuum signal between the throttle and the
supercharger inlet. Vacuum to the actuator pulls the bypass valve open during idle and light load conditions to decrease boost.
Engine Oil System
Engine lubrication is supplied by a variable displacement two-stage vane-type oil pump assembly. An oil control solenoid valve,
controlled by the engine control module (ECM), mounted to the oil pump provides two stage functionality. The oil pump is
mounted on the front of the engine block and driven directly by the crankshaft sprocket. The pump rotor and vanes rotate and
draw oil from the oil pan sump through a pick-up screen and pipe. The oil is pressurized as it passes through the pump and is
sent through the engine block lower oil gallery.
LT4 Wet Sump Engine
TITLE
ALL INFORMATION WITHIN ABOVE BORDER TO BE PRINTED EXACTLY AS SHOWN ON 8 1/2 x 11
WHITE 16 POUND BOND PAPER. PRINT ON BOTH SIDES, EXCLUDING TEMPLATES.
TO BE UNITIZED IN ACCORDANCE WITH GM SPECIFICATIONS.
19332622
IR 02JA18
PART NO.
DATE
17AU15
Initial Release - Rocko Parker
02JA18
Revision - Rocko Parker
5
SHEET
REVISION
35
OF
AUTH
ECA P5E00313
N/A
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