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Engine
About Engines
Writing a singular description of how an engine works is extraordinarily difficult. There are a multitude of
engine configurations and no one discourse can adequately cover them all. Despite this, there are a few primary
styles of engine design. The most commonly found engine is what's termed a 4-stroke engine. These may be found in
V, W or inline configurations, may have more than one cam shaft and many more internal bits than can be described
here. Traditionally, in vintage cars, you're most likely to find a V (e.g. V-8) or an inline type of engine.
Other types of engines are 2-stroke engines (which are fundamentally similar to 4-stroke) and rotary engines (which
are a science unto thmselves). For the sake of discussion here I will focus on 4-stroke engines.
Engine Components
A vehicle engine is comprised of the following elements at a minimum:
- Intake Manifold
- This is the entry point of the fuel/air mixture into the engine.
- Exhaust Manifold
- This is the exit point for the exhaust gasses resulting from the combustion in the engine.
- Head
- The Head component contains the valves, springs, and other parts necessary to
control the intake of fuel/air and the release of exhaust
- Cam Shaft
- The camshaft controls the opening and closing of the valves within the head. It is used to
manage the timing of the valve opening as well as the duration that the valve remains open.
- Spark plugs
- Spark plugs convert electrical energy to spark which is used to combust the air/fuel mixture
in the chamber.
- Distributor
- The distributor controls the delivery of electricity to the spark plugs. In modern cars this may be
replaced with computer controlled ignition and ignition coils.
- Piston
- The piston is the first point of translation of the combustion energy to mechanical energy. It is an
assembly that consists of the piston head, wrist pins, and connecting rod.
- Rings
- Rings are added to the head of the piston to improve its sealing properties against the cylinder
wall. This improved sealing minimizes lost enrgey and "blow-by".
- Crankshaft
- The crankshaft accepts the mechanical energy from the piston and translates it to rotational energy that
is then delivered partially back to the engine, but predominately to the transmission.
- Engine Block
- This is the core part to which everything is connected. It contains the cylinders, the journals for the crank,
water passages for cooling (unless it's an air cooled engine) and other engine specific items.
How it works
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The air/fuel mixture is delivered to the intake manifold from either a carburetor or fuel injection. As the
crankshaft rotates the belt attached to it causes the camshaft to rotate. The camshaft opens the intake valve(s)
and the air/fuel mixture is then drawn into the cylinder as part of the first stroke of the 4-stroke cycle ("suck").
The crankshaft continues to rotate causing the piston to perform a compression stroke ("squash"). At the height of
the stroke the rotor in the distributor meets the element in the distributor cap delivering electricity through the
wire to the spark plug (in more modern cars this is done by the computer and a coil at the plug). The spark plug
sparks, igniting the compressed air/fuel mixture. The explosion then forces the piston down turning the crank
creating the power stroke ("Bang"). Then, as the crank continues to turn the cam shaft is likewise turned opening the
exhaust valve. The piston then rises in the cylinder ushing out the exhaust gasses into the exhaust manifold ("Blow"). This completes
the 4-stroke cycle.
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Now, when you're talking about a single piston engine this is pretty simple. The reality is that you will never work on a
single piston engine. The complexity of all of this is managing how the various pistons are synchronized. The combination of
the crankshaft, camshaft(s), and distributor manage this process. The goal in this is that when any cylinder is fired, that
generated engery is used, in part, to work through the other three strokes in other cylinders in the engine.
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