What engine is the 6 cylinder inline: it is an engine with six cylinders mounted in a straight line along the crankcase with all the pistons driving a common crankshaft (straight engine).
What is the 6 cylinder inline displacement: it is in a range between 1829 cc and 6690 cc in recent model line up powertrain.
How much is the power of the 6 cylinders inline: the power of the 6 cylinders is in a range from 98 bhp to 510 bhp.
Which cars use 6 cylinder inline engine: mainly used for high end cars it is also sometimes used for smaller engines but these, although very smooth running, tend to be rather expensive to manufacture in terms of cost-to-power ratio.
Since the length of an engine is roughly proportional to the number of cylinders in one bank, the straight-six is necessarily longer than alternative layouts such as I4, V4, V6, or V8. The length of the straight-six was not a major concern in the older front-engine/rear-wheel drive vehicles. The modern move to the more space-efficient front-engine/front-wheel drive and transverse engine (left-to-right versus front-to-back) in smaller cars made the length of the V6 a major advantage and in recent years automobile manufacturers have replaced most of their straight-six engines with V6 engines.
Exceptions to the shift to V engines include BMW, which specializes in high-performance straight-sixes used in a lineup of front-engine/rear-wheel-drive vehicles, all of BMW's current 6-cylinder model line-up use the straight configuration, Volvo, which designed a compact straight-six engine/transmission package to fit transversely in its larger cars.
An inline six engine is in practically perfect primary and secondary mechanical balance, without the use of a balance shaft. The engine is in primary couple balance because the front and rear trio of cylinders are mirror images, and the pistons move in pairs (but of course, 360 degrees out of phase and on different strokes of the 4-stroke cycle). That is, piston #1 mirrors #6, #2 mirrors #5, and #3 mirrors #4, largely eliminating the polar rocking motion that would otherwise result.
Straight-six engines typically use a firing order of 1-5-3-6-2-4, which results in perfect primary and secondary balance.
The perfect balance has made the straight-six popular in some European sports-luxury cars, where smooth high-speed performance is very desirable.
Source:
https://en.wikipedia.org/wiki/Straight-six_engine
https://commons.wikimedia.org/wiki/File:Inline_6_Cylinder_with_firing_order_1-5-3-6-2-4.gif
edited by arrabbiata