Editing V6 engine (section)

== Design ==
Due to their short length, V6 engines are often used as the larger engine option for vehicles which are otherwise produced with inline-four engines, especially in [[transverse engine]] vehicles. A downside for [[luxury car]]s is that V6 engines produce more vibrations than [[straight-six engine]]s. Some sports cars like the [[Porsche 911]] use [[flat-six engine]]s instead of V6 engines, due to their near perfect primary [[engine balance]] and lower [[centre of gravity]] (which improves the [[Automobile handling|handling]]).

The displacement of modern V6 engines is typically between {{convert|2.5|and|4.0|L|cuin|0|abbr=on}}, though larger and smaller examples have been produced, such as the {{convert|1.8|L|cuin|0|abbr=on}} [[Mazda K engine|Mazda V6]] used in the 1991–1998 [[Mazda MX-3]],<ref>{{cite web |last1=Herriott |first1=Richard |title=Engines: The Road Less Traveled |url=https://driventowrite.com/2014/08/22/small-six-cylinder-engines/ |website=Driven to Write |access-date=2019-12-30 |date=22 August 2014}}</ref> or the {{convert|1.6|L|cuin|0|abbr=on}} [[Mitsubishi 6A1 engine#6A10|Mitsubishi V6]] engine used in the 1992–1998 [[Mitsubishi Mirage|Mirage]]/[[Mitsubishi Lancer|Lancer]], while the largest gasoline V6 built was the {{cvt|478|cuin|L|1|order=flip}} [[GMC V6 engine#478|GMC V6]] used in the 1962 [[Chevrolet C/K#Medium- & heavy-duty models|GMC C/K series 6500]]{{Broken anchor|date=2025-05-26|bot=User:Cewbot/log/20201008/configuration|target_link=Chevrolet C/K#Medium- & heavy-duty models|reason= The anchor (Medium- & heavy-duty models) [[Special:Diff/1055726102|has been deleted]].|diff_id=1055726102}}.

=== Balance and smoothness ===
All V6 engines with even firing spacing—regardless of the V-angle between the cylinder banks—are subject to a primary imbalance caused by each bank consisting of an [[inline-three engine]], due to the odd number of cylinders in each bank. Straight-six engines and flat-six engines do not experience this imbalance. To reduce the vibrations caused by this imbalance, most V6 engines use a [[harmonic damper]] on the crankshaft and/or a counter-rotating [[balance shaft]].

Six-cylinder designs have less pulsation in the power delivery than four-cylinder engines, due to the overlap in the power strokes of the six-cylinder engine. In a four-cylinder, four-stroke engine, only one piston is on a power stroke at any given time. Each piston comes to a complete stop and reverses direction before the next one starts its power stroke, which results in a gap between power strokes, especially at lower engine speeds (RPM). In a six-cylinder engine with an even firing interval, the next piston starts its power stroke 60° before the previous one finishes, which results in smoother delivery of power to the [[flywheel]].

Comparing engines on a dynamometer, a V6 engine shows instantaneous torque peaks of 154% above mean torque and valleys of 139% below mean torque, with a small amount of negative torque (engine torque reversals) between power strokes. In the case of a four-cylinder engine, the peaks are approximately 270% above mean torque and 210% below mean torque, with 100% negative torque being delivered between strokes. However, a V6 with uneven firing intervals of 90° and 150° shows large torque variations of 185% above and 172% below mean torque.<ref name="Kane">{{cite conference|first=Jack|last=Kane|title=Torsional Output of Piston Engines|work=Aircraft Engine Technology|publisher=EPI, Inc|year=2006|url=http://www.epi-eng.com/piston_engine_technology/torsional_excitation_from_piston_engines.htm}}</ref>

=== Cylinder bank angles ===
==== 10 to 15 degrees ====
[[File:Klepbediening VR6 24V.PNG|thumb|left|upright=0.5 |Cross-section of a VR6 engine]]
{{main |VR6 engine}}

Since 1991, Volkswagen has produced narrow angle ''VR6'' engines with V-angles of 10.5 and 15 degrees shared by both banks of cylinders, in a design similar to the 1922-1976 [[Lancia V4 engine]]. These engines use a single cylinder head so are technically a straight engine with the name "VR6" coming from the combination of German words “Verkürzt” and “Reihenmotor” meaning “shortened inline engine”. The VR6 engines were used in [[transverse engine]] front-wheel drive cars which were originally designed for inline-four engines. Due to the minimal extra length and width of the VR6 engine, it could be fitted to the engine compartments relatively easily, in order to provide a displacement increase of 60 percent .

Since there is no room in the V between the cylinder banks for an intake system, all the intakes are on one side of the engine, and all the exhausts are on the other side. It uses a firing order of 1-5-3-6-2-4 (which is the firing order used by most straight-six engines), rather than the common V6 firing order of 1-2-3-4-5-6 or 1-6-5-4-3-2.
{{clear left}}

==== 60 degrees ====
[[File:VG30E.jpg|right|thumb|1984-1999 [[Nissan VG engine#VG30E|Nissan VG30E]] 60-degree engine]]
[[File:Toyota 1GR-FE 4.0 Litre V6 Engine.jpg|right|thumb|[[Toyota_GR_engine#1GR-FE|Toyota 1GR-FE]] 4.0 Litre 60-degree V6 Engine]]

A V-angle of 60 degrees is the optimal configuration for V6 engines regarding engine balance.<ref name="caranddriver.com">{{cite web |title=The Physics of: Engine Cylinder-Bank Angles |url=https://www.caranddriver.com/features/a15126436/the-physics-of-engine-cylinder-bank-angles-feature/ |website=www.caranddriver.com |access-date=21 December 2019 |date=14 January 2011}}</ref> When individual [[crank pin]]s are used for each cylinder (i.e. using a six-throw crankshaft), an even firing interval of 120 degrees can be used. This firing interval is a multiple of the 60 degree V-angle, therefore the combustion forces can be balanced through use of the appropriate [[firing order]].

The inline-three engine that forms each cylinder bank, however, produces unbalanced rotating and reciprocal forces. These forces remain unbalanced in all V6 engines, often leading to the use of a [[balance shaft]] to reduce the vibration.

The 1950 Lancia V6 engine was pioneering in its use of a six-throw crankshaft in order to reduce vibration. More recent designs often use a three-throw crankshaft with 'flying arms' between the crankpins to allow an even firing interval of 120 degrees to be achieved. A pair of counterweights on the crankshaft can then be used to almost perfectly cancel out the primary forces<ref name="Nunney"/>{{refpage|page=16}} and reduce the secondary vibrations to acceptable levels.<ref name="Nunney"/>{{refpage|pages=13–16}} The engine mounts can be designed to absorb these remaining vibrations.<ref name="Nunney"/>{{refpage|pages=40–41}}

A 60 degree V-angle results in a narrower engine overall than V6 engines with larger V-angles. This angle often results in the overall engine size being a cube shape,{{citation needed|date=December 2019}} making the engine easier to fit either longitudinally or transversely in the engine compartment.

==== 90 degrees ====
[[File:ZS KV6.jpg|thumb|1996-2005 [[Rover KV6 engine|Rover KV6]] 90-degree engine<ref>{{cite web |title=1998 Rover 75 2.0 KV6 specifications, fuel economy, emissions, dimensions 79673 |url=https://www.carfolio.com/specifications/models/car/?car=79673 |website=www.carfolio.com |access-date=21 December 2019}}</ref>]]

Many manufacturers, particularly American ones, built V6 engines with a V-angle of 90 degrees based on their existing 90-degree V8 engines. Such configurations were easy to design by removing two cylinders and replacing the V8 engine's four-throw crankshaft with a three-throw crankshaft. This reduced design costs, allowed the new V6 to share components with the V8 engine, and sometimes allowed manufacturers to build the V6 and V8 engines on the same production line.

The downsides of a 90 degree design are a wider engine which is more vibration-prone than a 60 degree V6. The initial 90 degree V6 engines (such as the [[Buick V6 engine#Fireball V6|Buick Fireball V6]] engine) had three shared crankpins arranged at 120 degrees from each other, due to their origins from the V8 engines. This resulted in an uneven firing order, with half of the cylinders using a firing interval of 90 degrees and other half using an interval of 150 degrees. The uneven firing intervals resulted in rough-running engines with "unpleasant" vibrations at low engine speeds.

Several modern 90 degree V6 engines reduce the vibrations using split crankpins offset by 30 degrees between piston pairs, which creates an even firing interval of 120 degrees for all cylinders.<ref name="caranddriver.com"/> For example, the 1977 [[Buick V6 engine#231|Buick 231]] "even-fire" V6 engine was an upgraded version of the Buick Fireball engine with a split-pin crankshaft to reduce vibration by achieving an even firing order.<ref name="Nunney"/>{{refpage|page=16}}<ref>{{cite web |title=The Strange Tale of the Buick Special, Buick-Rover V8, and 3800 V6 |url=https://ateupwithmotor.com/model-histories/buick-special-skylark-rover-v8-3800-v6-history/ |website=www.ateupwithmotor.com |access-date=24 December 2019 |date=9 April 2008}}</ref> Such a 'split' crankpin is weaker than a straight one, but modern [[metallurgy|metallurgical techniques]] can produce a crankshaft that is adequately strong.

A balance shaft and/or crankshaft counterweights can be used to reduce vibrations in 90 degree V6 engines.<ref name="Nunney">{{cite book|last=Nunney|first=M J|title=Light and Heavy Vehicle Technology|edition=4th|publisher= Butterworth-Heinemann|year=2007|isbn=978-0-7506-8037-0}}</ref>{{refpage|pages=14–44}}

==== 120 degrees ====
At first glance, 120 degrees might seem to be the optimal V-angle for a V6 engine, since pairs of pistons in alternate banks can share crank pins in a three-throw crankshaft and the combustion forces are balanced by the firing interval being equal to the angle between the cylinder banks. A 120 degree configuration, unlike the 60 degree or 90 degree configurations, would not require crankshafts with flying arms, split crankpins, or seven main bearings to be even-firing. However, the primary imbalance caused by odd number of cylinders in each bank still remains in a 120 degree V6 engine. This differs from the perfect balance achieved by a 90 degree V8 engine with a commonly used [[crossplane]] crankshaft, because the inline-four engine in each bank of the V8 engine does not have this primary imbalance.

A 120 degree design also results in a large width for the engine, being only slightly narrower than a [[flat-six engine]] (which does not have the balance problems of the V6 engine). Therefore, the flat-six engine has been used in various automobiles, whereas use of the 120 degree V6 engine has been limited to a few truck and racing car engines, with the exception of the [[McLaren M630 engine]], which uses a 120 degree bank angle with a single balance shaft to eliminate all primary couples. The M630 also takes advantage of the wide angle by placing the turbochargers inside the vee, commonly referred to as a 'hot vee' configuration. The Ferrari 296 GTB is the first Ferrari road car to sport a V6 turbo with a vee angle of 120 degrees between the cylinder banks.

==== Other angles ====
Other angle V6 engines are possible but can suffer from severe vibration problems unless very carefully designed. Notable V-angles include:
* 45 degrees — [[EMD 567]] and [[EMD 645]] locomotive, marine and stationary Diesel engines. These engines were based on V8 and V16 engines which also used a V-angle of 45 degrees.
* 54 degrees — 1994-2004 [[GM 54-Degree V6 engine|General Motors 54-degree]] automotive engine. A slightly smaller than usual V-angle was used to reduce the width of the engine, allowing it to be used in small transverse-engine front-wheel drive cars.
* 65 degrees — 1956-1975 [[Ferrari Dino engine#65°|Ferrari Dino]] automobile engine. The V-angle was increased from the then-common 60 degree angle to allow larger carburetors to be used (for potentially higher power in race tuning). Crankpins with an offset of 55 degrees within every pair of cylinders were used to achieve the even firing interval of a 60 degree V6 engine. The 2009–present [[V9X engine|Nissan-Renault V9X]] automobile engine also used a 65 degree bank angle, to allow a turbocharger to fit between the cylinder banks.
* 72 degrees — [[Mercedes-Benz OM642 engine|Mercedes-Benz OM642]] [[BlueTEC]] diesel engine. This engine uses crank pins offset by 48 degrees, to achieve an even firing interval.
* 75 degrees — 1992-2004 [[Isuzu V engine]] used in the [[Isuzu Rodeo]] and [[Isuzu Trooper]]. These engines were produced in both SOHC and DOHC versions. A 75 degree V6 engine is also used by the 2016–2022 [[Honda NSX (second generation)|Honda NSX]]. 
* 80 degrees — 1988 [[Honda RA16 engine|''Honda RA168-E'' engine]] used in the [[McLaren MP4/4]] Formula One racing car.