AUTOMOTIVE
MANUFACTURING HISTORY INCLUDES TWO
burtal horsepower wars. The first involved gasoline engines
and started when the GI's rerurned from WWII. It ended with
the 1973 oil crisis. This oil embargo gave birth to the next
slow-starting and fierce-ended fued, which we are all veterans
of - the diesel horsepower wars. Notice how power levels have
recently leveled off? It's because in 2010, manufactures need
to address what's coming out the tailpipe just as much as they
have to worry about what number the engine makes. Since we're
optimistic and believe the past is a guide, we preict we'll
see the emission restrictions turn into a catalyst for better
performing diesel engines. Fortunately for us, a world without
problems is a very boring place for engineers.
THE LML DURAMAX
The 2011 diesel pickups built by GM will use the same basic 6.6L engine
GM has been using for the last decade. This signifies the original
Duramax engine's design was a good foundation - one the engineers
didn't need to totally change as we predicted with the 6.9L UMAX ("Detroit
Spy Report, April '07). Still, stricter future emissions requirements
are putting more pressure on the industry to improve the cleanliness
of diesel exhaust without giving up power. The rest of this article
highlights the new features on the 2011 Duramax trucks that enable
squeaky-clean diesel. Only the future knows for sure whether the new
emissions pressure will crush the diesel market into a cube - or a
diamond.
Coming
down the pipe for the 2011 Silverado and Sierra should be
larger-diameter brakes. We expect 13- to 14-inch rotors
The
torsion bar front suspension has been retained but features
more load capacity
1480
U-joints will be used to handle increased cargo and towing
capacities
The
AAM 11 1/2-inch ring gear rear axle will be carried over
The
body and interior stayed the same, but the chassis has been
redesigned in order to increase the gross vehicle weight
rating (GVWR)
DURAMAX
ENGINE HISTORY
01-04
LB7
Injectors
housed inside valve covers and no EGR, with the exception of California
models
04-06
LLY
Introduction
of Garrett VGT turbo and EGR
06-07
LBZ
Revised piston
design lowered compression ratio to 16.8:1 from 17.5:1, a stronger
block debuted, and a 32-bit ECU was introduced
07-10
LMM
Introduction
of DPF and exhaust aftertreatment
2011
LML
Extra fuel injector
placed behind turbo, urea injection, and dual-loop EGR system
2011
LGH
Detuned version
for 2500 and 3500 vans and will use GM's 6L90 six-speed transmission
instead of the Allison 1000
The
2011 Silverado and Sierra will see a larger opening in the front bumper.
This modification provides more airflow, and more cooling for the
new EGR system and transmission heat exchange. Sources say the new
EGR system will have a high and low temperature loop, providing an
increased flow rate and a larger window of opportunity for introducing
oxygen-depleted exhaust gas gack into the engine. The dead air cools
the cylinders and reduces nitrogen oxide (NOx) emissions.
The 2011
Duramax traded it slower solenoid injectors for quicker opening
and closing piezo units. The common-rail fuel system sprays diesel
up to 29,000 psi inside the combustion chamber
The 2011
Duramax incorporates urea injection, or as GM calls it, diesel
exhaust fluid (DEF). Bells and flashing lights indicate when the
DEF needs to be refilled. If the tank goes empty, the truck is
sent into limp mode.
GM added
a ninth injector after the turbo to supply the fuel needed to
creat heat that will burn off the emissions built up in the exhaust
aftertreatment system. A major benefit of this new system includes
not having to deal with oil dilution, which results from biodiesel
or regular diesel going past the piston rings and getting into
the crankcase. In addition, fuel economy should improve with this
more precise setup. Biodiesel compatible fuel lines, an additional
heating element in the fuel system, and the latest generation
coalescing filter bump the engine's biodiesel rating from B5 to
B20.
LML engine
This
article was written by Jason Thompson with photos courtesy of
General Motors.
This article was in Diesel Power magazine March 2010 edition.
