The clearest
explanation of how an engine works in my opinion
from a lawn mower company...
I'm no engineer. Although I could understand separate functions, how engines work is still something I couldn't put together in my head.
Up until I read this article.
Hopefully that'll be helpful for the van and further if I get into boat as I'm thinking of.
This link is an article about
" 4 common small engine problems and how to fix them" from the same website. That should be useful with the boating as I will probably start off with a
cruiser's 4 strokes than a narrowboat with
a diesel engine...
Understanding Small Engines
What are the essentials of a four-stroke engine?
The biggest difference between small engines and other types of
engines is their small capacity and simplicity of design. Small engines
generate very modest amounts of power - generally no more than 25 HP -
compared to a typical family car (up to 200 HP). And a small engine's
size makes it easier to maintain and repair.
Since small engines are designed for simple tasks like cutting grass
and turning soil, their designs are fairly uncomplicated. Unlike cars
and other vehicles that frequently accelerate, slow down or idle for
long periods, small engines either run at constant speed or change speed
slightly to handle modes changes in the "load," such as when a
lawnmower hits a patch of thick grass.
Also, unlike car engines, small engines don't have to fit under a
hood or make room for countless computers and other devices. This makes
small engine parts easier to install, adjust and remove. You can reach
most small engine parts with a few turns of a wrench.
Essentials Of The Four-Stroke Engine
Here, in its simplest form, is how a four-stroke engine works:
When you pull the rope, known as a rewind cord, or use your electric
starter, precise amounts of fuel and filtered air mix in the carburetor.
The mixture rushes into the engine to be compressed, ignited and burned
in a controlled process known as internal combustion. Hot gases are
produced. As the gases expand, they push a smooth, well-lubricated
cylindrical component, known as the piston. The piston, in turn, drives
the crankshaft, the arm that spins a blade or performs other work.
Valves let air and fuel into the combustion chamber above the piston and
allow spent gases to exit through the muffler.
The whole process involves four piston strokes and is designed to
become self-sustaining from the time the engine starts until the moment
it stops. Timed electrical surges cause the spark plug to fire
repeatedly inside the combustion chamber, igniting each fresh supply of
air and fuel and producing gases that continually drive the piston and
crankshaft.
All the while, oil from the crankcase and air circulate to keep
engine temperatures within an acceptable range, and a governor monitors
changes in the workload and adjusts engine speed accordingly.
Five Basic Systems
There are five systems at work in every small engine:
Fuel Supply,
Compression,
Ignition,
Lubrication/Cooling, and
Governor (speed control).
Two other common systems are also discussed in detail. Some engine
models - especially heavier-duty ones - may contain a starter motor,
which requires an electrical system to charge the battery.
Most small engines sold in the past 10-15 years include a braking
system as well. This is designed to protect you and others by stopping
the engine quickly if you let go of the controls.
In short, five systems generate the power to spin a blade, turn a
wheel or perform other work. Two others may be included for safety and
convenience. The following will familiarize you with the major parts in
these systems and the essentials of how they work.
Engine Components And Their Function
Here's how the components in your engine interact:
-
The rewind cord is pulled to start the combustion process. On
some models, a starter motor replaces the rewind, drawing on battery
power to start the engine.
-
Revolving magnets work in conjunction with the ignition armature and spark plug to produce a spark in the combustion chamber.
-
The carburetor draws in fuel from the fuel tank and outside air
to form a combustible vapor that is fed into the combustion chamber.
-
Intake and exhaust valve open and close at precisely timed
intervals to let air and fuel enter the engine and to let spent gases
exit.
-
The piston is pushed through the cylinder by the force of
expanding gases. The piston's motion causes the crankshaft to turn.
Momentum then carries the piston back toward the top of the cylinder.
-
Oil stored in the crankcase circulates through the engine to
lubricate key components like the piston and crankshaft and to provide
generalized cooling by drawing away heat from internal engine surfaces.
-
A flywheel brake and stop switch are included on engines for
equipment such as mower that require constant supervision. The two
components are designed to stop the engine if you release the controls.
-
An air vane or flyweights monitor engine RPMs so the governor can maintain the selected engine speed.
-
Cooling fins help reduce engine temperatures when air circulate across the hottest engine surfaces.
