Detroit Diesel Series 71
Encyclopedia
The Detroit Diesel Series 71 is a two-stroke cycle
diesel engine
series, available in both inline
and V
configurations, with the inline models including one, two, three, four and six cylinders, and the V-types including six, eight, 12, 16 and 24 cylinders. The three largest V units used multiple cylinder heads per bank to keep the head size and weight to manageable proportions, the V-12 and V-24 using two and four heads from the inline six-cylinder model, and the V-16 using four heads from the four-cylinder inline model. This feature also assisted in keeping down the overall cost of these large engines by maintaining parts commonality with the smaller models.
The inline six-cylinder 71 series engine was introduced as the initial flagship product of the Detroit Diesel Engine Division
of General Motors in 1938. The V-type first appeared in 1957. The 71 in the model series designation refers to the displacement per cylinder
in cubic inches (actually 70.93 cu in / 70.9312715 cid). Bore and stroke is the same to all units, at 4.25 x 5.0 inches (107.95 x 127 mm).
All Series 71 engines utilize uniflow scavenging, where a gear
-driven Roots type blower
mounted to the exterior of the engine provides intake air through cored passages in the engine block and ports in the cylinder walls at slightly greater than atmospheric pressure. The engine exhausts through pushrod-operated poppet valve
s in the cylinder head(s), with either two or four valves per cylinder. Unit fuel injection
is employed, one injector per cylinder, with no high fuel pressure outside of the injector body. The injectors are cycled from the same camshaft
responsible for opening the exhaust valves.
As a two-stroke diesel engine cannot naturally aspirate (draw in) intake air, a blower is necessary to provide sufficient air to scavenge exhaust gasses from the cylinders and support combustion. Later high-performance versions were available with turbochargers, and turbochargers with aftercooling, the turbochargers discharging into the Roots blower intake.
The most popular incarnations of the series 71 engine as used for highway vehicle applications included the inline 6-71, the V-block 6V-71 (both widely used in transit bus
es) and the 8V-71. In addition to motorcoach propulsion, both inline and V types have found extensive usage in truck
s, fire apparatus
, motor homes, construction and industrial machinery, and military vehicle
s and equipment. The 71 series is very popular in marine applications, not only as a propulsion engine in small craft but as auxiliary power to drive generators, winches and other heavy shipboard machinery.
The inline 6-71 engine, in all of its variations, was also available as a 'pancake engine' (here invariably called either 6L-71 or 6N-71) for horizontal (underfloor) mount applications, such as on larger Crown
and Gillig
school bus
es and articulated
puller transit buses (such as the Ikarus
286).
Over the years, the 71 series has enjoyed a reputation for dependability and ease of maintenance. Due to their ubiquity and operating characteristics, inline models acquired a variety of nicknames from those who used and serviced them. Most common were "Screaming Jimmy" (Jimmy being trucker slang for GMC trucks) or "Rocky Mountain Humming Bird," which terms referred to the engine's sound at full throttle. Other nicknames include "Green Leaker" and "Driptroit Diesel," referring to the powerplants' factory color and propensity for leaking oil on everything in or near the engine compartment. The v12 has been called the "Buzzin Dozen" due to the higher RPM needed for it to produce power and what sound it makes when the engine brake is on.
Two-stroke cycle
A two-stroke engine is an internal combustion engine that completes the process cycle in one revolution of the crankshaft...
diesel engine
Diesel engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...
series, available in both inline
Straight engine
Usually found in four- and six-cylinder configurations, the straight engine, or inline engine is an internal-combustion engine with all cylinders aligned in one row, with no offset...
and V
V engine
A V engine, or Vee engine is a common configuration for an internal combustion engine. The cylinders and pistons are aligned, in two separate planes or 'banks', so that they appear to be in a "V" when viewed along the axis of the crankshaft...
configurations, with the inline models including one, two, three, four and six cylinders, and the V-types including six, eight, 12, 16 and 24 cylinders. The three largest V units used multiple cylinder heads per bank to keep the head size and weight to manageable proportions, the V-12 and V-24 using two and four heads from the inline six-cylinder model, and the V-16 using four heads from the four-cylinder inline model. This feature also assisted in keeping down the overall cost of these large engines by maintaining parts commonality with the smaller models.
The inline six-cylinder 71 series engine was introduced as the initial flagship product of the Detroit Diesel Engine Division
Detroit Diesel
As a corporation, Daimler Trucks North America has decided to rename the company "DETROIT".Detroit Diesel Corporation is an American-based diesel engine producer headquartered in Detroit, Michigan, USA...
of General Motors in 1938. The V-type first appeared in 1957. The 71 in the model series designation refers to the displacement per cylinder
Engine displacement
Engine displacement is the volume swept by all the pistons inside the cylinders of an internal combustion engine in a single movement from top dead centre to bottom dead centre . It is commonly specified in cubic centimeters , litres , or cubic inches...
in cubic inches (actually 70.93 cu in / 70.9312715 cid). Bore and stroke is the same to all units, at 4.25 x 5.0 inches (107.95 x 127 mm).
All Series 71 engines utilize uniflow scavenging, where a gear
Gear
A gear is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part in order to transmit torque. Two or more gears working in tandem are called a transmission and can produce a mechanical advantage through a gear ratio and thus may be considered a simple machine....
-driven Roots type blower
Roots type supercharger
The Roots type supercharger or Roots blower is a positive displacement lobe pump which operates by pumping fluids with a pair of meshing lobes not unlike a set of stretched gears. Fluid is trapped in pockets surrounding the lobes and carried from the intake side to the exhaust...
mounted to the exterior of the engine provides intake air through cored passages in the engine block and ports in the cylinder walls at slightly greater than atmospheric pressure. The engine exhausts through pushrod-operated poppet valve
Poppet valve
A poppet valve is a valve consisting of a hole, usually round or oval, and a tapered plug, usually a disk shape on the end of a shaft also called a valve stem. The shaft guides the plug portion by sliding through a valve guide...
s in the cylinder head(s), with either two or four valves per cylinder. Unit fuel injection
Fuel injection
Fuel injection is a system for admitting fuel into an internal combustion engine. It has become the primary fuel delivery system used in automotive petrol engines, having almost completely replaced carburetors in the late 1980s....
is employed, one injector per cylinder, with no high fuel pressure outside of the injector body. The injectors are cycled from the same camshaft
Camshaft
A camshaft is a shaft to which a cam is fastened or of which a cam forms an integral part.-History:An early cam was built into Hellenistic water-driven automata from the 3rd century BC. The camshaft was later described in Iraq by Al-Jazari in 1206. He employed it as part of his automata,...
responsible for opening the exhaust valves.
As a two-stroke diesel engine cannot naturally aspirate (draw in) intake air, a blower is necessary to provide sufficient air to scavenge exhaust gasses from the cylinders and support combustion. Later high-performance versions were available with turbochargers, and turbochargers with aftercooling, the turbochargers discharging into the Roots blower intake.
Transit bus
A transit bus , also known as a commuter bus, city bus, or public bus, is a bus used for short-distance public transport purposes...
es) and the 8V-71. In addition to motorcoach propulsion, both inline and V types have found extensive usage in truck
Truck
A truck or lorry is a motor vehicle designed to transport cargo. Trucks vary greatly in size, power, and configuration, with the smallest being mechanically similar to an automobile...
s, fire apparatus
Fire apparatus
A fire apparatus, fire engine, fire truck, or fire appliance is a vehicle designed to assist in fighting fires by transporting firefighters to the scene and providing them with access to the fire, along with water or other equipment...
, motor homes, construction and industrial machinery, and military vehicle
Military vehicle
A military vehicle is a vehicle that includes all land combat and transportation vehicles, which are designed for or are in significant use by military forces throughout the world. Vehicles that are armored or intended for combat are often referred to as armoured fighting vehicles....
s and equipment. The 71 series is very popular in marine applications, not only as a propulsion engine in small craft but as auxiliary power to drive generators, winches and other heavy shipboard machinery.
The inline 6-71 engine, in all of its variations, was also available as a 'pancake engine' (here invariably called either 6L-71 or 6N-71) for horizontal (underfloor) mount applications, such as on larger Crown
Crown Coach Corporation
Crown Coach Corporation was a manufacturer of school buses and fire trucks located in southern California. Crown closed in March 1991 due to declining demand for school buses at the time.-History:Crown Coach Corporation was founded by Don M...
and Gillig
Gillig
Gillig Corporation, formerly Gillig Bros., is a manufacturer of heavy-duty low-floor transit buses located in Hayward, California. Prior to 1993, Gillig had also been a manufacturer of school buses.-History:...
school bus
School bus
A school bus is a type of bus designed and manufactured for student transport: carrying children and teenagers to and from school and school events...
es and articulated
Articulated bus
An articulated bus is an articulated vehicle used in public transportation. It is usually a single-deck design, and comprises two rigid sections linked by a pivoting joint...
puller transit buses (such as the Ikarus
Ikarus Bus
Ikarus is a bus manufacturer based in Budapest, Hungary. It was established in 1895 as Uhri Imre Kovács- és Kocsigyártó Üzeme .-History:...
286).
Over the years, the 71 series has enjoyed a reputation for dependability and ease of maintenance. Due to their ubiquity and operating characteristics, inline models acquired a variety of nicknames from those who used and serviced them. Most common were "Screaming Jimmy" (Jimmy being trucker slang for GMC trucks) or "Rocky Mountain Humming Bird," which terms referred to the engine's sound at full throttle. Other nicknames include "Green Leaker" and "Driptroit Diesel," referring to the powerplants' factory color and propensity for leaking oil on everything in or near the engine compartment. The v12 has been called the "Buzzin Dozen" due to the higher RPM needed for it to produce power and what sound it makes when the engine brake is on.
71 series variants
| Model | Displacement | Engine configuration | Horsepower |
|---|---|---|---|
| 1-71 | 1.2L (71ci) | Single-cylinder | 10 |
| 2-71 | 2.3L (142ci) | I-2 | 68 |
| 3-71 | 3.5L (213ci) | I-3 | 113 |
| 4-71 | 4.7L (284ci) | I-4 | 160 |
| 6-71 | 7.0L (426ci) | I-6 | 238 |
| 6V-71 | 7.0L (426ci) | V-6 | 238 |
| 8V-71 | 9.3L (568ci) | V-8 | 318 |
| 12V-71 | 14.0L (852ci) | V-12 | 450 |
| 16V-71 | 18.6L (1136ci) | V-16 | 635 |
| 24V-71 | 27.9L (1704ci) | V-24 | 1800 |
| Model Codes | |
|---|---|
| T | Turbocharged |
| V | V-Block configuration |
| L or N | Low profile |