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DESCRIPTION & OPERATION
Belt Drive System
The belt drive system uses a single 10-rib poly-v
belt to drive the alternator, water pump, and fan
drive (Figure 20). A separate single-v belt,
running off the water pump pulley, drives the
refrigerant compressor. The service life of the
poly-v belt is considerably improved over other
systems and allows the use of higher horsepower
cooling fans.
Both manually tensioned and automatically
tensioned systems are used. Whether an engine
has the manually tensioned or automatically
tensioned system depends on the specific engine
configuration and application.
20
Figure 20 — Belt Drive
J-Tech™ Engine Brake
The J-Tech™ engine brake is a vehicle-slowing
device that allows the engine to act as an air
compressor, producing retarding horsepower that
helps slow the vehicle. The braking action is
accomplished through hydraulics using a master-
slave piston arrangement similar to a hydraulic
jack. When the engine brake is operated, a single
exhaust valve opens near top dead center of the
compression stroke, releasing high-pressure air
out the exhaust. Opening one exhaust valve,
instead of two, significantly reduces load to the
engine brake and the valve train without
adversely affecting braking power. Releasing
compressed air to the exhaust prevents the
return of energy to the engine piston on the
expansion stroke. The result is a net power loss
from the engine, or retarding horsepower, used to
slow the vehicle.
With the J-Tech™ engine brake unit, the master
piston of a given cylinder activates the slave
piston of that same cylinder, providing optimum
timing of the compression release. The E-Tech™
engine uses the same engine brake unit on the
front and rear cylinder head.
1. Air Conditioner
Compressor
2. Water Pump
3. Alternator
4. Poly-V Belt
5. Tensioning Device
5_106_00.bk Page 24 Friday, August 4, 2000 11:17 AM
BDC for engine manuals and specs