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So even if you are into cars or not, most people are familiar with the fact that the bigger the engine, the more power it can generate, translating to more acceleration, top speed, and or torque (power).   I say in most circumstances because an engine can be boosted with other ways outside the engine to grant the car more power, but it all starts at the engine.   The more cylinders the engine has, the bigger they are because the more gas they can combust.   Most cars run on 4, 6 or 8 cylinders and there are some super or exotic cars with 10, 12 or more cylinders.   We’re going to talk about the 6-cylinder engine, its variants, and the benefits or shortcomings between the Inline 6, the V6 and the flat 6 engine.

The Inline 6 Engine

This engine has 6 cylinders or pistons that are all lined up in one row, one after another, all facing the same way in the engine block.  With the amount of space this engine takes they are all lined up, plus the necessary transmission components that need to be placed at either end of the engine, it is a very long engine.  One of BMW’s most predominate sport cars the M3 uses the inline 6 engine.

Benefits of an inline 6 engines

  • Balance – Since all the pistons are lined in a row and as they rotate they keep a symmetry. As a result, they don’t vibrate as much.
  • Reliable – This a simple arrangement of valves that because of its balance and lack of vibration it is a reliable engine as well.
  • Ease of Accessibility to components – Sparkplugs can be accessed directly from the top of the engine and you don’t have to open up the engine to change.

Disadvantages of an inline 6 engine

  • Because of its size it doesn’t fit in typical body frame profiles. Its two long to arrange for front wheel drive.
  • They tend not to be as fuel efficient.
  • Generally inline 6 engines are more expensive to manufacture and to make compliant to emission regulations.

The V6 Engine

Now instead of all 6 cylinders lined up in a row, these engines have their valves paired and angled in a V shape.  They are normally set at a 60 or 90 degree angle from each other.  They are widely used because of their benefits but are also, not without their shortcomings.

Benefits of a V6 Configuration

  • This is a more compact configuration so they take up less room in the cabin, so in turn they are cheaper to design and fit in more body profiles.
  • The extra room under the hood from their small size means you can more easily install turbo chargers or intakes so they can be made to be very powerful.
  • They also can be fit inside easier into small cars creating a high power to weight ratio, meaning high performance sport cars.

Disadvantages of a V6

  • Because of the valves moving in different directions the V6 engine doesn’t enjoy the same balance.
  • The smaller size and an increase in components necessary means the engine is harder to work on and increases the cost for repair.
  • Increase in complexity means an increase in possible failure lessening its reliability.
  • To increase power many models use twin cams. In the event of a timing belt failure while driving it can potentially destroy the engine.  This kind of damage can also be inspected with the use of a borescope.

Flat 6 Engine

The flat 6 engine also known as a Boxster engine is like a V engine except instead of an angle the pistons are arranged with the V in a 180 degrees with 3 pistons in one direction each with a matching horizontally opposed piston in the opposite.

Advantages of a Flat 6

  • These engines generate a large amount of torque so they can create some exciting sport cars like the Porsche Cayman or the Subaru Impreza
  • They have the lowest center of gravity and are very stable as well which results in better handling and cornering.
  • Easier to make safer since it is lower in profile it, in the event on an extreme head on collision it is positioned to go underneath the passenger compartment rather than into the passenger compartment.

Disadvantages of a Flat 6

  • Although they are lower in profile they are wider as well. That width makes it extremely difficult to work around and perform maintenance without special tools like borescopes.
  • The Engine block is split in 2 halves so it requires two complex items to be manufactured adding to cost.
  • The transmission normally needs an added complexity as well. A disadvantage Subaru gets around by making their vehicles AWD.

So, the best 6-Cylinder Engine is?

It can be reasoned that they all have their place depending on application.   There is a bit of a trade off when it comes to cost vs performance vs reliability.   The inline 6 wins in reliability but the performance tends to suffer without great expense invested into the cost.   The V6 because of its lower costs can more easily take power upgrades but at the price of reliability since it is more complex.  The flat 6 offers some fantastic performance benefits and is relatively reliable due to its stability but are expensive to build and to maintain due to its complexity.