Editing V12 engine (section)

== Design ==
=== Balance and smoothness ===
Each bank of a V12 engine essentially functions as a [[straight-six engine]], which by itself has perfect primary and secondary [[engine balance]]. A four-stroke V12 engine has even firing order at V-angles of 60, 120, or 180 degrees<ref>. Engine Configuration and Smoothness Autozine Technical School https://www.autozine.org/technical_school/engine/Smoothness2.html
autozine.org
</ref>{{Unreliable source?|date=December 2024|sure=y|reason=personal website}} Many V12 engines use a V-angle of 60 degrees between the two banks of cylinders.<ref>{{cite book|last=Nunney |first=Malcolm James |title=Light and Heavy Vehicle Technology |edition=Fourth |publisher=Butterworth-Heinemann |year=2007 |pages=13–14 |isbn= 978-0-7506-8037-0}}</ref> V12 engines with other V-angles have been produced, sometimes using split [[crankpin]]s to reduce the unbalanced vibrations. The drawbacks of V12 engines include extra cost, complexity, friction losses, and external size and weight, compared with engines containing fewer cylinders.

At any given time, three of the cylinders in a V12 engine are in their power stroke, which increases the smoothness of the power delivery by eliminating gaps between power pulses.

A V12 engine with a 180 degree V-angle is often called a [[flat-twelve engine]]. These are also sometimes called '[[Flat engine#Boxer engine|boxer]] twelve' engines, however this terminology is incorrect for the majority of 180-degree V12 engines, since they use shared crankpins and are therefore not configured as true boxer engines.<ref>{{cite news |url=https://airandspace.si.edu/collection-objects/rolls-royce-condor-ia-v-12-engine |title=Rolls-Royce Condor IA, V-12 Engine |date=2016-03-10 |work=National Air and Space Museum |access-date=2017-05-24 |language=en |archive-date=2017-08-24 |archive-url=https://web.archive.org/web/20170824095342/https://airandspace.si.edu/collection-objects/rolls-royce-condor-ia-v-12-engine |url-status=dead }}</ref>

Theoretically, the rotating parts of a V12 racing engine could be lighter than a crossplane V8 engine of similar displacement due to the V12 engine not requiring counterweights on the crankshaft or as much inertial mass for the flywheel. In addition, the exhaust system of a V12 engine is much simpler than would be required for a crossplane V8 engine to achieve pulsed exhaust gas tuning. However, the use of V12 engines in motor racing is uncommon in the 21st century.

=== Size and displacement ===
A 60-degree V12 engine is typically narrower than a 90-degree V6 or V8 engine of similar displacement. However, the V12 engine is usually longer than V6 and V8 engines. The added length often makes it difficult to fit a V12 engine into a passenger car, but the length is not typically a problem for trucks and stationary applications. Due to its narrower width, the V12 is common as locomotive, armoured tank, and marine engines. In these applications, the width of the engine is constrained by tight [[Loading gauge|railway clearances]] or [[Lane|street widths]], while the length of the vehicle is more flexible.

In twin-propeller boats, two V12 engines can be narrow enough to sit side by side, while three V12 engines are sometimes used in high-speed three-propeller configurations. Large, fast cruise ships can have six or more V12 engines. In historic piston-engine fighter and bomber aircraft, the long, narrow V12 configuration used in high-performance aircraft made them more streamlined than other engines, particularly the short, wide [[radial engine]].