1. History

2. Design
    Nomenclature  Applications 

3. 71 series variants

4. Further developments
     WWII General Motors 6004/6046 engine {{anchor|GMC 6004}}   Detroit diesel 6051 quad-71  Soviet/Russian copies 

5. See also

6. References

7. Sources

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 {{convert|70.93|cid|cc|abbr=on}}.

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.

The 71 Series went off of the market in the summer of 1995, and the four stroke Detroit Diesel engine was introduced as a replacement.

Design

Bore and stroke are the same across all units, at {{convert|4+1/4|×|5|in|mm|0|abbr=on}}. 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 (as viewed from the front of the engine). The less-common Left Hand engines were typically used in buses and boats because that engine rotation direction matched with rear-engined transverse installations in buses and the propeller rotation in boats.

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 than atmospheric pressure. The engine exhausts through pushrod-operated poppet valves 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.

Nomenclature

The first number refers to the number of cylinders in the engine, followed by a dash ("-") or "V", indicating an inline block or a vee-block, respectively, and then 71 for the Series designation. The 71 in the model series designation refers to the nominal displacement per cylinder in cubic inches, a rounding off of {{convert|70.93|cid|cc|abbr=on}}.

The suffix denotes additional engine features. Engines fitted only with a blower are referred to as "naturally aspirated" (SAE designation) and have an N suffix in the model designation, e.g., 8V-71N is a V-8 "naturally aspirated" Series 71 engine. Later high-performance versions were available with turbochargers, and turbochargers with intercooling, the turbochargers discharging into the Roots blower intake. Such engines have a T suffix in the model designation, e.g., 8V-71T.

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 (both widely used in transit buses) 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 (Gray Marine 6-71) 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' (here variably called either 6L-71 or 6N-71) for horizontal (underfloor) mount applications, such as on larger Crown and Gillig school buses and articulated puller transit buses (such as the Crown-Ikarus 286).

71 series variants

Further developments

WWII General Motors 6004/6046 engine {{anchor|GMC 6004}}

The inline 6-71 was adapted to British requirements as the power plant for Canadian (and later British) built Valentine tanks where it was known as the GMC 6004, orders being placed in late September 1940.^[15]

The 6046 Diesel was a twin engine setup used by US and British tanks and tank destroyers.

• The M3A3 (Lee IV/Lee V) and M3A5 (Grant II) variants of the M3 tank
• M4A2 Sherman tank
• M10 tank destroyer and the re-gunned British variant the 17pdr SP Achilles
• M36B2 variant of the M36 tank destroyer

Detroit diesel 6051 quad-71

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(L). The eight engines produced a total of {{convert|1600|bhp|0|abbr=on}}.^[16]

Soviet/Russian copies

In the Soviet Union / Russia, various versions of this engine-type were produced at the Yaroslavl automobile factory (YaAZ).^[17] Throughout World War II, the 4-71 engine both in locally assembled form (built by Lend-Lease provided American industrial equipment) and from USA-supplied kits had been used for Ya-12 light artillery tractors^[18] 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".^[17] 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.^{[19][20][21][22][23]}

See also

• List of Detroit Diesel products

References

Sources

• Shelton, Chris. "Then, Now, and Forever" in Hot Rod, March 2017, pp.16-29.

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