The Detroit Diesel Series 71 is a two-stroke diesel engine series, available in both inline and V configurations. The first number in the model series designation refers to the number of cylinders, and the second - 71 - the nominal displacement per cylinder in cubic inches, a rounding off of. Inline models included one, two, three, four and six cylinders, and the V-types six, eight, 12, 16 and 24 cylinders. The two largest V units used multiple cylinder heads per bank to keep the head size and weight to manageable proportions, the V-16 using four heads from the four-cylinder inline model and the V-24 using four heads from the inline six-cylinder model. This feature also assisted in keeping down the overall cost of these large engines by maintaining parts commonality with the smaller models.
History
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. Sales of The 71 Series ceased in the summer of 1995, with the four stroke Detroit Diesel engine introduced as a replacement.
Design
Bore and stroke are the same across all units, at. Inline models were famously "symmetrical", meaning that blower, exhaust, water manifold, starter, and other components could be mounted on either side of the basic block to fit a particular application. A number of models could also run with the crankshaft turning either clockwise or counter-clockwise, called "Right Hand" or "Left Hand" rotation engines. The less-common Left Hand engines were typically used in buses, because the rotation matched rear-engined transverse installations. Boats equipped with two engines would typically use one Left Hand and one Right Hand, so that the torque from the propellers would cancel each other out, without the need for a complex reversing gear on one side. As a two-stroke diesel engine that does not use crankcase aspiration cannot naturally draw in combustion air, the blower is inherently necessary to charge the cylinders with air for combustion. The blower also assists in scavenging spent combustion gasses at the end of the power stroke. All Series 71 engines use uniflow scavenging, in which a gear-driven Roots 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 thanatmospheric pressure. The engine exhausts through pushrod-operated poppet valves in the cylinder head, 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.
Nomenclature
The first number refers to the number of cylinders in the engine, followed by a hyphen or "V", indicating inline or vee, respectively, then 71 for the Series designation, referring the nominal displacement per cylinder in cubic inches. Like most Detroit Diesel two-cycle engines, the 71 Series are equipped with a blower yet still referred to as "naturally aspirated". These do not have a model suffix identifier: 6-71 is an inline 6. When the model number includes a suffix, it denotes additional features. Engines equipped with needle unit fuel injectors and commonly four exhaust valves per cylinder are indicated by the suffix "N", so for the V8, 8V-71N. Later versions were available with turbochargers, which discharged directly into the Roots blower intake; these have a "T" suffix, and with aftercooling, a "TA", so 8V-71T or 8V-71TA. "TT" indicates Tailored Torque and "TTA" Tailored Torque Aftercooled. These models are designated for economy and constant horsepower ratings.
Applications
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 and the 8V-71 V-8. In addition to motorcoach propulsion, both inline and V types have found extensive usage in trucks, fire apparatus, motor homes, construction and industrial machinery, a few farm tractors, commercial fishing vessels, and military vehicles 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 Detroit inline 6-71 engine, in all of its variations, was also available as a 'pancake engine' for horizontal mount applications, such as on larger Crown and Gilligschool buses and articulated puller transit buses. Many 4-71 motors were used in various construction equipment, such as many Galion highway graders.
Variants
Family
Model
Torque
Power
Length × Width × Height
Weight
3-71
3-71
@ 1400 rpm
@ 2100 rpm
4-71
4-71
@ 1600 rpm
@ 2100 rpm
4-71
4-71T
@ 1400 rpm
@ 2100 rpm
6-71
6-71
@ 1600 rpm
@ 2100 rpm
6-71
6-71T
@ 1400 rpm
@ 2100 rpm
6-71
6-71TT
@ 1200 rpm
@ 1950 rpm
6V-71
6V-71
@ 1600 rpm
@ 2100 rpm
6V-71
6V-71T
@ 1600 rpm
@ 2100 rpm
8V-71
8V-71
@ 1600 rpm
@ 2100 rpm
8V-71
8V-71T
@ 1600 rpm
@ 2100 rpm
8V-71
8V-71TA
@ 1200 rpm
@ 2100 rpm
8V-71
8V-71TTA>
@ 1600 rpm
@ 2100 rpm
12V-71
12V-71
@ 1600 rpm
@ 2100 rpm
12V-71
12V-71T
@ 1600 rpm
@ 2100 rpm
16V-71
16V-71TI
@ 1600 rpm
@ 2100 rpm
Model Numbers
Further developments
WWII General Motors 6004/6046 engine
The inline 6-71 was adapted to British requirements as the power plant for Canadian built Valentine tanks where it was known as the GMC 6004, orders being placed in late September 1940. The 6046 Diesel was a twin engine setup used by US and British tanks and tank destroyers.
The Detroit diesel 6051 quad-71 was a Detroit Diesel Series 6-71 side by side tandem engine setup of two banks of four engines each driving two propeller shafts in Landing Craft Infantry LCI. The eight engines produced a total of.
Soviet/Russian copies
In the Soviet Union / Russia, various versions of this engine-type were produced at the Yaroslavl automobile factory. Throughout World War II, the 4-71 engine both in locally assembled form and from USA-supplied kits had been used for Ya-12 light artillery tractors and trucks. After 1945, the 4-71 engine entered production in a slightly modified configuration to suit the conditions of the Soviet Union branded "YaAZ-204". After 1947 the factory used a copy of the 6-71 engine branded "YaAZ-206" in the YaAZ 200 / 210 / 214 series of heavy trucks built from 1947 to 1960. Production was transferred to KrAZ in Kremenchug, Ukraine in 1959, where newer versions of the YaAZ-206 stood in production until the appearance of the four-stroke V8-engined KrAZ-255 in 1967.
