Diesel Mechanics: Advanced Knowledge Required
Diesel engine principles are pretty straight forward for the
experienced mechanic but what about regular everyday people who have
never taken the time to find out more about a diesel engine and how it
works?
I am going to explain in layman's terms the basic principles of a diesel engine.
WHAT'S THE DIFFERENCE BETWEEN A GASOLINE ENGINE AND A DIESEL ENGINE?...a quick overview.
The
first thing you should know is a gasoline engine and a diesel engine
are totally different. A gasoline engine is constructed much lighter
than the heavier built diesel engine and runs on an air/fuel mixture
combined with a high energy spark that is timed to ignite the air/fuel
mixture inside each engine cylinder at the precise time creating power
and torque [turning force] which drives your vehicle.
A diesel
engine uses high compression [intake air that is compressed / squished]
into a very small space inside each cylinder causing extreme heat! This
is called 'Heat Of Compression' which ignites a very fine high pressure
mist of diesel fuel that is injected into the cylinder at the exact
time.
So you now know that a gasoline engine needs a high energy spark to run while a diesel uses 'Heat Of Compression'
The Four Stroke Principle
Every
engine today runs on FOUR STROKES or FOUR CYCLES- both these terms mean
the same. Here is how the four stroke diesel engine operates.
The
four strokes are: INTAKE-COMPRESSION-POWER-EXHAUST. The pistons, valves
and injectors work together in each cylinder in a set sequence over and
over.
1} INTAKE STROKE:
Intake valves in the cylinder head
open allowing pressurized air to enter each cylinder while the piston
is travelling downward.{the pressurized air supply is made possible by
the TURBOCHARGER which pushes air into the intake system giving the
diesel engine a boost of air to keep up with instantaneous injection of
fuel}
2} COMPRESSION STROKE:
When the piston starts to make
it's way back upward the valves close which traps the intake air in the
cylinder which allows compression to take place, the HEAT OF
COMPRESSION is reached when the piston reaches the top of the cylinder,
the diesel fuel is then injected into the cylinder at the precise time.
3} POWER STROKE:
After
injection takes place an explosion occurs in the cylinder because of
the combination of heat and atomized diesel fuel. This causes the
piston to be forced downward which produces torque and the horsepower
required from a typical diesel engine.
4} EXHAUST STROKE:
After
the power stroke the piston moves upward once again while the exhaust
valves open allowing the previously ignited gases to escape to the
atmosphere out the exhaust system.
As mentioned before each
cylinder goes through this exact sequence over and over in a set firing
order. For instance, a 6 cylinder diesel engine has a firing order 1-
5- 3- 6- 2- 4 This is the order that each cylinder goes by, following
the 4 strokes mentioned above. This sequence has been engineered to
allow the diesel engine to run smoothly with no imbalance.
DIESEL ENGINE TRIVIA: Today's high performance diesel engines
Fuel passes through the injector at speeds of nearly 1500 miles per hour - as fast as a jet plane at top speed.
Fuel is injected into the combustion chamber in less than 1.5 milliseconds, the same time it takes for a camera flash to go off.
The minimum amount of fuel injected into a diesel engine is one cubic millimetre - about the same volume as the head of a pin.
Volkswagen
has developed a 1 litre diesel powered car that got 100 kilometres out
of .89 litres of fuel {60 miles on approxiamately 3/4 of a quart of
fuel!}
There is much to learn about diesel engines and a ton of
information online. If you have ever considered buying a vehicle with a
diesel engine you have my blessing! The extra cost will be to your
benefit, so I recommend finding out more about diesel engines before
you decide which one to choose.
