[0:00] just about everyone knows that a typical
[0:03] automobile gets its power from an engine
[0:05] under the hood
[0:06] but how many people can say they
[0:07] actually know how that engine works
[0:11] while a modern internal combustion
[0:13] engine is obviously an extremely complex
[0:15] piece of machinery
[0:16] the basic principle behind it is pretty
[0:18] simple let's take a closer look
[0:21] at a high level a gasoline engine can be
[0:23] thought of somewhat like an air pump
[0:25] except that the exhaust coming out is
[0:27] more of a side effect
[0:28] this pump's real purpose is to rotate an
[0:31] internal shaft which in turn rotates the
[0:33] vehicle's wheels
[0:35] it does this by connecting that shaft
[0:37] called a crankshaft
[0:38] to pistons that move due to a mixture of
[0:40] air and gasoline combusting inside their
[0:42] cylinders
[0:44] which creates a sort of chain reaction
[0:45] that keeps the engine turning
[0:48] before getting deeper into this process
[0:50] let's first touch on the two main parts
[0:52] of an engine
[0:54] on the bottom a lower block is home to
[0:56] the pistons
[0:57] cylinders and crankshaft the latter of
[1:00] which sends the engine's power out to
[1:02] the transmission and wheels
[1:04] and above the head contains the top of
[1:07] the cylinders
[1:08] and manages their airflow and combustion
[1:10] through valve train fuel injection
[1:13] and ignition systems so let's explain
[1:15] that part a little more
[1:17] you may have heard the term force drunk
[1:19] to describe a vehicle engine
[1:21] this refers to its four stages of
[1:24] operation
[1:26] first the piston moves down creating a
[1:28] vacuum in the cylinder chamber that
[1:30] pulls air in through precisely
[1:31] controlled intake valves
[1:34] next the valves close and the piston
[1:36] raises back up
[1:37] compressing all that air along with some
[1:40] gasoline that was mixed in from the fuel
[1:41] injection system
[1:44] now the fun part the ignition system
[1:46] creates a spark at the end of the spark
[1:48] plug
[1:48] creating a controlled explosion of
[1:50] compressed air and fuel that sends the
[1:52] piston back down
[1:55] then finally the piston moves back up
[1:58] pushing that spent air fuel mixture
[2:00] through the exhaust valves and out to
[2:01] the
[2:02] you guessed it exhaust pipes
[2:05] and since we're dealing with multiple
[2:07] cylinders with pistons all working from
[2:09] the same crankshaft
[2:10] each one essentially creates the
[2:12] four-stroke process for the next one
[2:14] pretty ingenious right now
[2:17] speaking of multiple cylinders let's
[2:20] talk about the various
[2:21] engine configurations four-cylinder
[2:24] engines are probably the most common
[2:25] design these days
[2:27] but who doesn't love a v6 or even a v8
[2:31] these terms simply refer to the number
[2:33] of cylinders in the engine
[2:34] and their layout nearly all
[2:36] four-cylinder engines have their
[2:38] cylinders arranged in a row
[2:40] called inline or straight but it's also
[2:43] pretty typical to see
[2:44] engines group their cylinders into two
[2:46] banks connected at an angle
[2:48] a v doing it this way effectively cuts
[2:50] the engine length in half
[2:52] enabling it to fit more easily under the
[2:54] hood so a v6
[2:56] three cylinders on either side creating
[2:59] a v-shape
[3:00] and what if that v-shape was opened up
[3:02] all the way
[3:03] a 180 degree angle well then you'd have
[3:06] what's called a boxer or flat
[3:08] engine design all right so what about
[3:12] those other numbers you always see
[3:14] 2.0 3.5 well that refers to the engine's
[3:18] displacement
[3:19] often simply thought of as its size
[3:22] that number is literally the volume in
[3:24] liters that the pistons displace with
[3:26] every engine cycle so essentially if you
[3:29] were to fill up the cylinders of a
[3:31] 2-liter engine with liquid
[3:33] it would take well 2 liters and if it's
[3:36] a 4-cylinder engine
[3:37] each one displaces half a liter
[3:41] so what's the end result of all this
[3:43] power
[3:44] the measurable output of an engine is
[3:46] called its torque
[3:47] basically the strength with which it
[3:49] turns its crankshaft
[3:51] torque is measured in pound-feet which
[3:53] as the name implies
[3:54] is the force created by one pound of
[3:56] weight at a distance of one foot
[3:59] imagine a one pound weight sitting at
[4:01] the end of a one foot wrench
[4:03] that nut is being turned with one pound
[4:05] foot of torque
[4:07] so now going back to the displacement
[4:09] concept bigger cylinders pull in more
[4:12] air and fuel typically resulting in more
[4:15] muscle
[4:15] they turn the crankshaft with more force
[4:18] which is perfect for large vehicles
[4:20] towing or even just spirited driving so
[4:23] now you're probably thinking isn't that
[4:25] horsepower
[4:26] well yes and no in fact horsepower
[4:29] doesn't technically exist okay
[4:32] yes that requires a bit of explanation
[4:35] horsepower is obviously a real thing but
[4:37] it's actually a calculation
[4:39] not a physical measurement like torque
[4:41] is it's basically torque over time
[4:45] so this means the faster that engine
[4:47] turns its revolutions per minute or rpm
[4:50] the more work it can do and the more
[4:52] horsepower it has
[4:54] put in extremely simplified terms torque
[4:56] times rpm
[4:58] equals horsepower but that doesn't mean
[5:01] making big horsepower is as simple as
[5:03] spinning the engine faster
[5:05] since that takes more and more energy as
[5:07] the engine speed increases
[5:09] and as that torque decreases the
[5:11] horsepower calculation eventually can't
[5:13] keep up either
[5:14] this is also why transmissions are so
[5:17] critical in keeping everything in the
[5:18] appropriate
[5:19] sweet spot but that's a topic for
[5:21] another video
[5:22] so that's the general idea behind
[5:25] internal combustion engines
[5:26] but this was just a high level look at
[5:28] the basics engines 101 if you will
[5:31] there's obviously a whole lot more to
[5:33] say about engine tech
[5:35] so be sure to check out the other videos
[5:36] in this series to learn more