Electronic fuel injection control system Both the
normal (L56) and heavy-duty emissions certified (L65) versions of
GM's turbo diesel engine utilize an electronic fuel-injection
control system. This major technological enhancement incorporates a
powertrain control module (PCM) that controls both the engine and
transmission, an electronic throttle control and an electronically
controlled fuel-injection pump. The adaptation of electronics to the
rotary injection pump yields almost complete freedom to schedule
fuel quantity and timing at optimal values for every speed and load
point. What does all of this mean to the customer? Increased fuel
economy, the elimination of black and white exhaust, improved cold
weather starting, enhanced idle quality and reduced noise levels.
The electronic fuel delivery system also helps protect the engine
from overheating and other abuses, and allows GM to be fully
compliant with current emissions standards. GM was the first
manufacturer to introduce an electronically controlled fuel
injection system in diesel pickup trucks.
The fuel injection pump was upgraded in 1997 and again in 1999
for improved durability by improving the Optical Sensor Tracking
Encoder (OSTE) circuit board. In addition, the steel rollers in the
pump were replaced with ceramic rollers for longer life. This system
also makes available three electronically controlled Power Take Off
(PTO) speeds. They are 1070 RPM, 1360 RPM, and 1600 RPM. These
speeds can be activated by a simple switch.
Turbocharging When GM set out to design the 6.5L V8
diesel engine, the goal was to build an engine that was reliable and
durable, with unparalleled performance. From the start, the 6.5L was
designed specifically for turbocharging. The secret weapon behind
the 6.5L turbo diesel is the GM computer controlled wastegate. This
wastegate allows the turbocharger rotor speed and boost to be
electronically adjusted as altitude and engine speed change, and as
torque is needed. The wastegate helps the engine work harder, but
only when it needs help. When you need torque, it's there; when it's
not required, the wastegate does not overwork the engine. The payoff
is impressive fuel mileage, smooth, quiet operation and the
necessary power to complete the job. This uniquely designed
wastegate turbocharger delivers quick throttle response during
acceleration and reduces turbo-boost pressure after obtaining
maximum torque. The wastegate is designed to prolong turbo life and
help manage the overall stress on internal engine components.
On-Board Diagnostics Second Generation (OBDII) As
with all GM vehicles, GM's L56 and L65 turbo diesel engine is fully
OBDII compliant. This required significant enhancements to the
powertrain control module (PCM). The PCM, a highly sophisticated
on-board computer, received a 50-percent increase in memory and
improved diagnostic capabilities in 1996. The PCM, which began
controlling the fuel-lift pump and air conditioner in 1996, also
monitors sensor systems such as coolant temperature, fuel
temperature, air temperature, barometer, exhaust gas recirculation
(EGR) pressure, turbo boost pressure and the thermostat diagnostic.
This technology will help GM vehicles meet the new, more stringent
emissions regulations, as well as improve idle stability. Misfire
detection was added to OBDII in 1998.
Turbocharging system On the G-van application of the
L65, a center mounted turbocharging system shortens the air and oil
passages and provides direct flow from the block. This design
eliminates the need for oil lines, which increases reliability,
durability, and serviceability. Oil is fed and drained directly from
the block mount. Fuel-manager filter system Each of GM's
diesel engines feature the fuel-manager filter system. This system
is a double-filtration fuel filter that incorporates the filter, a
water separator and a fuel heater all in one canister. The top-load
vertical design and location simplify filter cartridge
Common serpentine accessory belt drive The 6.5L V8
diesel engine features a single serpentine belt for all the driven
components. Its automatic tension adjuster improves belt life and
makes servicing easier.
Fuel economy Among the many superior characteristics
of the 6.5L turbo is its exceptional fuel economy. When matched
against a comparably performing big-block V8 gasoline engine, this
diesel has the potential for 25 to 80 percent better fuel economy.
The improved fuel economy is a result of precise control of
combustion and more precise transmission control, both due to
Crankshaft bearings The crankshaft bearings used in
the 6.5L are made of a fatigue-resistant material that promotes a
higher bearing stress life. The rear crankshaft seal is in one piece
to reduce the chances of leakage.
Bulkhead The 6.5L diesel engine bulkhead area is
designed to handle the higher-cylinder firing pressures of a
turbocharged engine. In addition, the coolant passages and the oil
galleries are sized to provide the increased flow required by a
Combustion chamber To provide smokeless performance
and meet stringent emissions standards without sacrificing power,
the 6.5L is designed with an optimized combustion chamber. This
design provides an optimum balance of air in the prechamber, head
and cylinder that ensures a more even and complete burning of fuel.
For 1999 the compression ratio has been reduced to 19.5:1 and an
exhaust pressure regulator system was added to eliminate white
Modulated exhaust gas recirculation system In
addition to having an optimized precombustion chamber, the 6.5L L56
turbo engine utilizes an electronically controlled modulated exhaust
gas recirculation system. This allows for more precise control over
the flow of exhaust gas and also helps to meet stringent emissions
Adaptive cylinder balance Adaptive cylinder balance
is included on the 6.5L turbo diesel. This process measures the
horsepower of each cylinder at idle and directs fuel to each
cylinder accordingly. This results in smoother operation of the
vehicle by minimizing the vibration of the engine.
Cylinder block The cylinder block incorporates
piston spray cooling for increased engine life. This is accomplished
by installing spray nozzles in the bulkhead that spray of oil at the
underside of the piston. An increased flow oil pump and lubrication
system ensure sufficient oil pressure during all running conditions.
The oil cooler lines and oil coolers have increased in size so that
they provide a 100% increase in flow through the oil cooler.
Cooling system The cooling system has been upgraded
with an increased flow water pump and new water crossover and dual
full-blocking thermostats. For 1999 the water pump bearing has been
improved for greater durability.
Catalytic converter The catalytic converter was
removed for 1999 while continuing to meet all emission
Oil pan capacity In 1999 the oil pan capacity
increased to eight quarts, which reduces