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Technology Corner Duramax  Diesel

The Isuzu - General Motors Story
A look at where this team came from and where it's headed!

* Over 60 different diesel engine models.
* Fuel efficient - Clean.
* Powerful beyond expectation.
* Durable, reliable diesel power

Isuzu, the global engine producer with production facilities in North America, Turkey, Poland, Japan, China, and Thailand.

Isuzu has focused on providing clean, reliable, durable diesel power for over 60 years. The Isuzu diesel is everything a diesel engine can be, and more.

1936 Isuzu Diesel TruckIn 1936 Isuzu launched its first diesel power plant. Now, 66 years later, Isuzu is supplying well over 300,000 diesel engines yearly to General Motors.

GM and Isuzu entered into a capital agreement in 1971. That relationship continued to flourish and grow, and in 1997 GM and Isuzu agreed that Isuzu would become the global C.O.E. (Center of Expertise) for diesel engine development within General Motors.

One year later, GM and Isuzu formed a joint venture for the development and production of the 6.6 liter Duramax Diesel.
The Duramax 6600 Turbo Diesel was the product to meet a rather bold goal.

That goal was to design, build, and deliver the most powerful diesel engine for use in a full size, light duty pickup truck.
Today, General Motors' new line of heavy-duty pickup trucks are consistently increasing diesel engine market share. The Duramax 6600 Turbo Diesel was voted as one of "Ward's Communications" 10 best engines for the year 2001.

Duramax Diesel 6600 Engine

Duramax 7800 crossection

The Duramax Diesel 6600 is produced in Moraine, Ohio. The GM / Isuzu relationship is growing stronger daily, with a commitment from both companies to remain dedicated to continually improving the quantity and quality of GM diesel powered pickup trucks. In terms of diesel engine production, Isuzu is poised to become the dominant diesel engine provider in North America.

When it comes to diesel engines, General Motors relies on Isuzu to provide the most technologically advanced diesel power. The introduction of the new Duramax Diesel 7800 is showing the world that together they can design and build competitive, powerful, and reliable diesel engines for use around the world.

GM is committed to using Isuzu diesel power in all its trucks. Offering an additional advantage for GM customers of "One Stop Shopping" for all parts, service, maintenance, and repairs. The GM dealer is certified, equipped, and ready to handle all Isuzu maintenance, repair, and service needs.

This eliminates the GM medium duty truck customers having to watch their GM trucks head out the door of the GM dealership and down the road to a separate, independent diesel engine service center. This new Duramax Diesel 7800 is now in Chevrolet Kodiak, GMC Topkick, and all GM's T-series.

The Duramax Diesel 7800 is an "Inline 6" commercial truck diesel, currently used in well over 300,000 trucks worldwide.

GM's confidence in the Duramax Diesel 7800 is high enough to make it the only engine available for the 2003 GMT 560 T-series Tilt Cab that will be available in early 2003.

The Duramax Diesel 7800 is available in horsepower configurations ranging from 200 HP all the way up to the "High Torque" 275 HP Version

Duramax Chevy Tow 560        GMC 560 Stake Body

    Duramax 7800  -   200 HP Version

Duramax Diesel 7800 Specifications

Duramax 7800 200 Horsepower
Displacement 7.8 Liters / 475.9 Cubic Inches
# of Cylinders 6 In Line
Bore 4.53 Inches
Stroke 4.92 Inches
Compression Ratio 16.0 : 1
Dry Weight 1180 pounds
Fuel Grade # 2 Diesel
Engine Power 200 HP @ 2200 RPM
Torque 520 pound Feet @ 1450 RPM
Governed full load setting 2400 RPM
No Load Governing speed 2550 RPM
Low-Idle, Curb Idle 600 RPM

    Duramax 7800 High Torque - 275 HP Version

This engine uses the exact same displacement and compression ratio as listed above, and has the same fuel grade requirements. It is tuned to produce the power ratings shown below.

Engine Power 275 HP @ 2200 RPM
Torque 860 Pound feet @ 1450 RPM

The Governed full load setting, no load governing speed, and curb idle remain the same as the 200 Hp Version listed above. The power range includes 200, 215, 230, 250, and the High Torque 275 Horsepower versions.

Duramax Diesel 10 Keys:
The 10 technological advantages that distinguish the Duramax Diesel according to Isuzu:

Ladder Frame Construction: (cylinder block)
Light Weight
High Rigidity
Reduced noise
Reduced Vibration
High Pressure Fuel Injection
Low Noise Level
Low Vibration
Fuel Economy
Precision Machined Fit Sleeve
Durability / Reliability
Nitrided Crankshaft
Durability / Reliability
Overhead Cam Layout (OHC)
Low emissions
Good Fuel Economy
Viscous Rubber Type Damper
Low Noise
Low Vibration
4-Valve Layout
Low Emissions
Good Fuel Economy
Axial Oil Seals
Durability / Reliability
Pistons with Cooling Channel
Durability / Reliability

Oil Cooler w/ Temperature Regulator Valve
Fast Warm Up.


The most important part of any engine is the cylinder block. To be durable and reliable, it must be very strong, especially in the "Bottom End", or crankshaft main bearing webs. A strong bottom end determines the "rigidity" of the Powertrain, including the transmission.

Duramax Nitrided Crankshaft
Duramax Nitrided Crankshaft

Isuzu research indicates that "Ladder Frame Construction" of the cylinder block provides significant increases in both reliability and durability. It minimizes the cylinder block bending moment and counters the vibration mode that tries to deform the main bearings. Remember, the main bearings are responsible for converting all the combustion energy from up-and-down motion to rotational motion.

Accomplishing that requires a significant amount of strength and rigidity in the main bearing area. Ladder frame construction provides that strength. Furthermore, the increased rigidity significantly improves Powertrain noise and vibration characteristics (NVH) and contributes greatly to exceptional durability. Experimental model analysis and FEM frequency response analysis contributed to the development of the single piece construction used for the cylinder block's bottom wall. This wall serves as the both the crankcase, and the crankshaft support area-bearing cap to further increase the rigidity of the crankshaft support area.

The next area of quality is the precision machining quality found in every Duramax. The "Precision Machined Fit Sleeves" of the Duramax offer several benefits. Service personnel will be pleasantly surprised with the ease of sleeve replacement, even after long periods of engine use. The precision fit sleeves offer a major cost savings during the engine overhaul, eliminating the need for cylinder reboring. The Duramax 7800 cylinder bore configuration offers the advantages of both "Parent Bore" and "Wet Liners" while avoiding the pitfalls traditionally associated with each.

Traditionally, camshafts, pushrods, and tappets were all part of a diesel engine in the Duramax power range. This classic valve train arrangement does lend itself well to designers tasked with meeting rigorous government emission standards and customer needs of the 21st Century.

Space that could be used for increasing engine block rigidity, or more effective valve porting (to improve engine breathing), was instead dedicated to the valve train and its operation.


By going to an overhead cam design with four valves per cylinder, and roller rocker arms in direct contact with the camshaft, the need for tappets and pushrods was eliminated.

Duramax Roller Rocker Arms Duramax Roller Camshaft
Duramax Roller Rocker Arm Assembly Duramax Roller Rocker Arms Duramax Roller Camshaft

The designers realized the ability to substantially increase block rigidity while providing engine symmetry, with the fuel injection nozzles located in the center of the cylinder.

This gives more even fuel distribution, which reduces black smoke, Nox, and particulate matter. This strategic injector placement results in better fuel distribution in the combustion chamber, resulting in more effective combustion chamber swirl, for smoother, more efficient operation. This design also contributes to greatly reduced NVH (Noise, Vibration, and Harshness) and exceptional durability.

As power and performance go up, so do internal engine temperatures. Efficient, effective temperature control throughout the engine is critical. Without proper cooling, engine power drops, noise levels increase, blow-by gases increase, and eventual piston failure and / or seizing occurs in the cylinder bore.

To end that, the Duramax is designed with high performance cooling throughout, with special attention to oil cooling. But nowhere is controlling more critical that at the pistons. In fact, the ability to lower and control the piston thermal load is key to durability and reliability in the high output diesel.

Piston Cooling Jet
Piston Cooling Jet

High piston temperature can cause material strength to drop. It can also lead to component cracking, oil carbonizing in the ring grooves, rings sticking, and piston to bore seizing. The Duramax is designed to control piston temperature through a number of design features, including proper sized cooling channels, optimum

Duramax piston

 cooling system architecture, ensuring temperature balance between oil inlets and outlets, and maintaining the correct oil volume. The Duramax 7800 uses a "Piston Cooling Jet" connected to the main oil gallery. It injects oil into the piston oil cooling channels to cool the piston and lubricate the piston pin.


Fuel Injection System

Duramax 7800 Denso Common Fuel Rail Duramax 7800 Denso Common Fuel Rail.

The Duramax 7800 uses a Denso common rail fuel injection system with pilot injection. The common rail design allows the engine's computer to independently control fuel injection, which allows for optimizing emissions and power. This common rail fuel system greatly increases fuel economy, and significantly reduces NVH.
Denso Fuel Pump

Denso Fuel Pump

This new fuel injection system is further enhanced by the "Closed Loop" fuel control system's self-diagnosing feature. This feature monitors engine conditions like engine speed, accelerator pedal angle, coolant temperature, and others, and feeds the data back to the fuel injection algorithm calculations. The results are greatly increased fuel economy, power, and responsiveness with reduced emissions.


Duramax 7800 Pilot injector

The pilot injection system injects a small amount of fuel just prior to the conventional fuel injection pulse. Pilot injection helps the Duramax 7800 to lower NOx emissions, improve cold starting and cold responsiveness, reduced knock and noise, and overall increased combustion efficiency.


Duramax 7800 Combustion chamber showing 4-valve layout with fuel injector in center for increased efficiency.

General Motors and Isuzu have shaken up the light truck world with the introduction of the Duramax 6600 and the Duramax 7800. These engines will meet all proposed 2004 model year diesel engine emission requirements. You can be sure that these technically innovative products will increase the competition in this arena tremendously as North America turns to diesel power for all it's needs.

I thought you would enjoy one last picture. Happy Motoring!

Sam Memmolo


Pictures and some information above supplied by General Motors and Isuzu.

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