The "competition"..summary of changes to the Duramax for 2002

[Chris N5CWM]

I clipped this from the 6.2/6.5 GM Diesel site.

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LB7 Truck Engine
"Duramax 6600"
Model Year 2002

SUMMARY OF NEW OR CHANGED FEATURES FOR 2002

Exhaust Gas Recirculation (EGR) for California
Revised Cylinder Heads for California
Catalytic Converter for California
Accessory Drive Belt Tensioner Relocated
Software for Engine Control Module (PCM)

FULL DESCRIPTIONS OF NEW OR CHANGED FEATURES

EXHAUST GAS RECIRCULATION (EGR) FOR CALIFORNIA
To meet new Low Emissions Vehicle (LEV) standards for medium-duty vehicles, 6.6L LB7s built for registration in
California will be equipped with EGR. The system
features a unique cooling process that increases its effectiveness. Hardware required includes: plumbing that
carries some exhaust gas from the turbocharger outlet to
the intake ports; an EGR control valve; an intake throttle plate that creates vacuum to induce the flow of exhaust
gas back into the combustion chambers; and a
stainless steel cooling element. The cooling element bolts to the right side of the engine block, inside the cylinder
head, with jackets fed by engine coolant.
Returned exhaust gas passes through a spiraled passage in the element, and the temperature of the gas is lowered
before it returns to the combustion process. The
EGR valve and intake throttle are managed by the PCM.

REVISED CYLINDER HEADS FOR CALIFORNIA
Heads for California 6.6L LB7s have a new, slightly different casting which modifies the intake ports to
accommodate EGR. The ports are repositioned relative to the
combustion chamber, entering the chamber at a slightly greater angle and increasing the swirl or mixing effect
inside the chamber. More swirl is necessary to
thoroughly blend returned exhaust gas with the air-fuel mixture.

CATALYTIC CONVERTER FOR CALIFORNIA
California 6.6L LB7s will be equipped with a catalytic converter supplied by Delphi. This high-capacity converter
measures 309 cubic inches in volume. LB7s built
for registration outside of California will not have the catalytic converter.

ACCESSORY DRIVE BELT TENSIONER RELOCATED
The device that automatically adjusts tension on the 6.6L LB7's serpentine accessory drive belt has been
relocated. The tensioner has essentially swapped positions
with one of the idler pulleys: The pulley is now located outside the belt, while the tensioner is inside. A new,
slightly longer drive belt is required to accommodate
the change (Gates PV6). The new location provides a more stable mounting for the tensioner, minimizes its
movement and extends its anticipated life.

SOFTWARE FOR ENGINE CONTROL MODULE (ECM)
Control software has been revised for model year 2002 in cooperation with Delphi, the ECM supplier. The new
program was developed primarily to accommodate
EGR for California, but it will be used to manage ECMs on all 6.6L LB7s.

The control software includes thousands of calibration values and potentially millions of variables-essentially
"switches"-that allow Powertrain engineers to turn on,
turn off or adjust various engine management operations, from ignition timing to fuel delivery. The switches must
be programmed in the software; engine
management engineers then calibrate-or set-those switches for the desired result. The 6.6L LB7's software adds
more switches to manage more functions, including
the EGR system on engines for California. The ECM is shipped with the control software installed; control
calibrations for the engine and specific application are
then ''flash programmed'' (as with a compact flash card reader on a personal computer) into the ECM at the truck
assembly plant.

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