Detroit V-71 Series Two Stroke Diesel

Detroit Diesel 71 Series

The Detroit 71 series is a family of two cycle diesel engines produced by Detroit Diesel, once a subsidiary of General Motors. The series was introduced in 1938, although it only featured inline engines until 1957. Early inline 71 series engines included a single, two, three, four, and six cylinder engine. Later V block engines were manufactured in six, eight, twelve, sixteen, and twenty-four cylinder configurations. All engines from the 71 series feature similar design characteristics, including 71 cubic inches of displacement per cylinder derived from the identical 4.25 inch bore and 5.00 inch stroke. The Detroit 71 Series engines were featured in a broad range of applications, including military and emergency services, generators, agricultural equipment, industrial and construction machinery, buses and motorhomes, and on-highway tractors.

Although all engines featured a roots type blower (or blowers), these engines are considered naturally aspirated per Detroit Diesel's manufacturing and advertising data. A turbocharged and turbocharged/aftercooled version was available in many engine configurations. Naturally aspirated engines contain a "N" behind the model designation (8V-71N, for example), while turbocharged engines feature a "T" (8V-71T, for example) and turbocharged/aftercooled engine contain a "TA" (8V-71TA, for example). To avoid confusion, the term aftercooled is synonymous with what is most commonly referred to today as intercooled. Certain configurations were also available in a "low profile" design to expand possible applications. Producing 1,800 horsepower, the 24 cylinder 24V-71 engine is somewhat of a rarity and was produced in low numbers for marine applications.

Two Stroke Diesel Fundamentals

A two stroke diesel operates on the same 2 cycle principles as a two stroke gas engine, however the design and operational characteristics have significant differences. Two stroke diesel engines do not require a fuel-oil mixture, nor do they rely on fuel for lubrication; they feature a conventional crankcase filled with engine oil. Unlike many two cycle gas engines, a two stroke diesel requires a typical exhaust valve arrangement and thus a camshaft, although there are no intake valves and air is drawn in through the cylinder liner in the same fashion that a two cycle gas engine draws in its intake air charge.

The two stroke Detroit diesels all feature a roots type blower to create positive pressure in the cylinder during the intake stroke. This pressure creates a scavenging effect and is used to evacuate the exhaust gases from the cylinder during the combined intake and exhaust strokes. Two stroke diesel engines tend to display the following advantages:

• Higher thermal efficiency than a comparable 4 stroke engine, translating into favorable fuel efficiency.

• High power density (horsepower per unit of displacement)

• Engines are reversible and can be run in both clockwise and counterclockwise rotations (ideal for many marine applications that require a reversible engine).

Detroit 6V-71 & 8V-71 Specs

Note - horsepower and torque figures often varied considerably by application and the following values are an approximate range of available ratings.

Detroit 12V-71 & 16V-71 Specs

Note - horsepower and torque figures often varied considerably by application and the following values are an approximate range of available ratings.