Automobile Repair/Engine

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For now, because this section is under construction, pick up some basic information at wikipedia which doesn't really cover the topic from an angle of the understanding needed to repair a variety of cars, but still has much useful information.

Because automotive systems are complicated and can be unintuitive to people who have never thought about them before, and people learn differently. In each system, there will be multiple explanations, so that visuals may complement words, and one way of explaining it may be complemented by another, etc.

The basics: The modern automotive engine summarized in...[edit | edit source]

A paragraph with highlighted terms[edit | edit source]

Summary[edit | edit source]

Air enters the engine and is mixed with gasoline to form an air-fuel mixture. This gasoline vapor mixture enters the cylinders of the engine, (which are, as the name implies, cylindrical containers) through an intake valve (a kind of flap that can open or close). The piston compresses the air-fuel mixture and the sparkplug ignites the mixture, forming a small fiery explosion within the cylinder which pushes the piston outward. The piston then (on momentum from its connecting rod) pushes the exhaust out, and is refilled with the air-fuel mixture again. This is called the four-stroke cycle. The movement of the piston (as propelled by the combustion of the air-fuel mixture) is turned into rotational motion by a connecting arm, and the rotational motion from all of the pistons is used to turn a crankshaft. The rotation of the crankshaft is the main purpose of the engine. The rotation of the crankshaft provides the power for all systems powered by the engine. The crankshafts rotational power is used both to turn the camshaft (another shaft, usually above the cylinders, whose rotation mainly functions to open and close the intake and exhaust valves of the engine in time with the four-stroke cycle) and is transferred via the flywheel to the transmission.

A vocabulary of its prominent parts with definitions[edit | edit source]

Engine Block
The "body" of the engine. This refers to either the shell of the engine, or the shell and all the parts of the engine housed within.
A space in which a piston travels and in which air is introduced, pressurized, combusted, and then leaves as the core part of the engine process.
Housed within the cylinders it moves in an up and down motion. The piston is connected via a connecting rod (conrod) to the crankshaft which converts linear motion into rotational motion.
A cylindrical component which sparks to ignite the air-fuel mixture during the compression phase of the four-stroke cycle.
Each cylinder of the engine requires at least one intake and at least one exhaust valve (most engines have one of each). The intake valve blocks and lets in the engine's air-fuel mixture into a single cylinder to later be ignited. The exhaust valve blocks and lets out the burned exhaust gas of its cylinder into the exhaust system.
Connecting Rod
connects pistons to crankshaft in a way that serves as kind of a flexible, mobile "joint" that allows the up-and-down motion of the piston to be driven by and drive the crankshaft.
Cylinder Head
the ends of a cylinder. Contains the intake valve and the exhaust valve for each cylinder. The piston comes in the other end. Its central purpose is to seal off air around the cylinder, so the piston can do its job (pressurize the chamber)
OHV (OverHead Valve, also known as l-heads or push rods.)
SOHC and DOHC (Single and Double OverHead Cam)

Small hardened rods that receive the upward "push" from the lifters and push the rocker arms. (Note: non-exsistant on overhead cam motors "OHC/DOHC")

Rocker arm
in an OHV/pushrod/l-head engine design, the rocker arm converts radial movement from either a push rod or directly by a cam lobe of the camshaft, into linear movement against a valve stem
Timing Chain, or instead Timing Belt

Two different parts designed to serve roughly the same purpose. Most engines use one of these to connect the camshaft to the crankshaft to synchronize the camshaft so that it makes one revolution for every two revolutions of the crankshaft. Timing chains are more durable, but timing belts are cheaper to replace and do not require lubrication. Sometimes they synchronize other parts as well.

the initial rotating part in the car, turned entirely by the connecting rods of the piston, and constituting a staged, crooked shaft with "pedals" the connecting rods hook onto.
a plate or disk about a foot in diameter attached to the back of the crankshaft that because of its inertia (that is, its mass. That is, it's heavy) it smoothes out the normal cylinder combustion pulses, reducing vibration. On manual transmission, it is a heavy iron disk that doubles as part of the clutch. On automatic, it is a stamped steel plate that mounts the heavy torque converter.
Throttle plate
controls whether air enters engine. controlled by gas pedal.

Visual representation[edit | edit source]

In-depth: What goes on in an engine[edit | edit source]