Nobody around the world can claim not to have been affected by the renowned Detroit Diesel engine in some way, whether they were aware of it or not. This straightforward, very versatile engine served as a workhorse throughout World War II, powering practically all major North American road vehicles, including buses, fire engines, and various heavy equipment. The Detroit Diesel engine, sometimes commonly referred to as "Green Leakers," "Screemin Jimmies," or simply "Jimmy," is widely used to power various workboats and fishing boats, and continues to be used today.
The Detroit Diesel Engine
An engine that would contribute to the end of World War II and grow to be one of the most adaptable ever produced was unveiled in 1938. Diesel-powered trains' superiority over steam-powered ones had previously been established by its bigger sibling, the EMD (Electro Motive Division). A two-stroke design would enable power users to provide the security and toughness of a diesel, when often a gas engine would be employed, with its excellent weight to horsepower ratio.
Detroit Diesel Series 71
The Series 71 was initially only offered as an inline engine with three, four, and six cylinder options by the Diesel Engine Division of General Motors. Eight, twelve, sixteen, and twenty-four cylinder versions of later V block engines were produced. Similar design elements are shared by all engines in the 71 series, notably the 71 cubic inches of displacement per cylinder that results from the same 4.25 inch bore and 5.00 inch stroke.
Detroit Diesel's production and advertising statistics classify these engines as naturally aspirated even though each engine included a roots style blower (or blowers). In many engine configurations, a turbocharged and turbocharged/aftercooled version was offered. A "N" follows the model number for naturally aspirated engines (8V-71N, for instance), a "T" for turbocharged engines (8V-71T), and a "TA" for turbocharged/aftercooled engines (8V-71TA, for example).
To clear up any misunderstandings, the terms intercooled and aftercooled are interchangeable. To broaden conceivable applications, some combinations were also offered in a "low profile" design. The 24 cylinder 24V-71 engine, which has 1,800 horsepower and is rather uncommon, was created in small quantities for marine purposes.
Two Stroke Detroit Diesel Engine
Although a two-stroke diesel engine functions on the same two-cycle principles as a two-stroke gas engine, there are important differences in the design and operational characteristics. Two-stroke diesel engines use a normal crankcase filled with engine oil instead of requiring a fuel-oil combination or relying on fuel for lubrication.
Although there are no intake valves and air is pulled in through the cylinder lining in a manner similar to how a two cycle gas engine sucks in its intake air charge, a two stroke diesel requires a standard exhaust valve arrangement and consequently a camshaft.
The roots type blower is a common component of two-stroke Detroit diesel engines and is used to generate positive pressure in the cylinder during the intake stroke. During the combined intake and exhaust strokes, this pressure produces a scavenging effect that is employed to remove the exhaust gases from the cylinder. The advantages of two-stroke diesel engines typically include the following:
• Better fuel efficiency due to higher thermal efficiency compared to a comparable 4 stroke engine.
• High power density (horsepower per unit of displacement)
• The rotation of the engines can be switched between clockwise and counterclockwise (ideal for many marine applications that require a reversible engine).
Detroit Diesel Engines Specs for 6V-71 & 8V-71
Due to their widespread use in on-highway applications, the 6V-71 and 8V-71 are two of the most well-known engines in the 71 series family. The 24V-71, on the other hand, is the least common of the series because only a limited number were made for specific marine applications.
| 6V-71N, 6V71T | 8V-71N, 8V-71T | |
| Manufacturer | Detroit Diesel | |
| Applications | On-highway, emergency services, generator sets, motorhomes, transit buses, agricultural equipment, industrial, military | |
| Configuration | V-6 | V-8 |
| Type | Two-cycle diesel | |
| Displacement | 426 cid (7.0 liters) | 568 cid (9.3 liters) |
| Compression | 17.0:1 (6V-71T) 18.7:1 (6V-71N) | 17.0:1 (8V-71T) 18.7:1 (8V-71N) |
| Bore | 4.25 in (108 mm) | 4.25 in (108 mm) |
| Stroke | 5.00 in (127 mm) | |
| Injection | Mechanical unit injector fuel system | |
| Aspiration | Naturally aspirated (6V-71N) and turbocharged (6V-71T) versions produced. All engines feature a roots type blower to provide exhaust gas scavenging. | Naturally aspirated (8V-71N) and turbocharged (8V-71T) versions produced. All engines feature a roots type blower to provide exhaust gas scavenging. |
| Oil Capacity | Varies by application | |
| Weight | 2,000 - 2,100 lbs | 2,300 - 2,500 lbs |
| Peak Horsepower | 238 hp @ 2,100 rpm (naturally aspirated, 6V-71N) 307 hp @ 2,100 rpm (turbocharged, 6V-71T) | 318 hp @ 2,100 rpm (naturally aspirated, 8V-71N) 385 @ 2,100 rpm (turbocharged, 8V-71T) |
| Peak Torque | 514 lb-ft @ 1,200 rpm (naturally aspirated, 6V-71N) 834 lb-ft @ 1,200 rpm (turbocharged, 6V-71T) | 863 lb-ft @ 1,200 rpm (naturally aspirated, 8V-71N) 1,112 lb-ft @ 1,200 rpm (turbocharged, 8V-71T) |
Detroit Diesel Engines Specs for 12V-71 & 16V-71
| 12V-71N, 12V-71T, 12V-71TA | 16V-71N, 16V-71T, 16V-71TA | |
| Manufacturer | Detroit Diesel | |
| Applications | On-highway, emergency services, generator sets, motorhomes, transit buses, agricultural equipment, industrial, military | |
| Configuration | V-12 | V-16 |
| Type | Two-cycle diesel | |
| Displacement | 852 cid (13.97 liters) | 1,136 cid (18.62 liters) |
| Compression |
17.0:1 (12V-71T, 12V-TA) 18.7:1 (12V-71N) |
17.0:1 (16V-71T, 16V-TA) 18.7:1 (16V-71N) |
| Bore | 4.25 in (108 mm) | |
| Stroke | 5.00 in (127 mm) | |
| Injection | Mechanical unit injector fuel system | |
| Aspiration | Naturally aspirated (12V-71N) and turbocharged (12V-71T, 12V-71TA) versions produced. All engines feature a roots type blower to provide exhaust gas scavenging. | Naturally aspirated (16V-71N) and turbocharged (16V-71T, 16V-71TA) versions produced. All engines feature a roots type blower to provide exhaust gas scavenging. |
| Oil Capacity | Varies by application | |
| Weight | 3,800 - 4,000 lbs | 4,600 - 4,800 lbs |
| Peak Horsepower | 450 - 900 hp @ 2,100 - 2,300 rpm | 630 - 760 hp @ 2,100 rpm |
| Peak Torque | 1,200 - 1,750 lb-ft @ 1,200 - 1,400 rpm | 1,700 - 2,200 lb-ft @ 1,200 - 1,400 rpm |
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