to move them around the planet? Actually a small percentage take advantage of that knowledge. Most
leave that sort of thing to a mechanic. Many people feel the engine compartment is too complicated to
understand without years of experience. And some mechanics prefer that the less you know the better
for their business. Which is fine because people need to earn a living. I say, as long as that mechanic is
going to tell you the truth. But when your vehicle costs you money in fuel , maintenance, etc., you should
know something about how it works. This will save you money and headache in the long run. This will also
help you to know how to improve the performance of the motor. Show you how to save fuel cost.
Here I have put together the start of a series of posts to help you understand how the motor in your car
works. Later we will explore how to save by keeping the motor and the other parts of your car Easily
maintained. As well, in future posts we will explore how to save fuel and to eventually lose our dependence
on oil based products. And if you want to see how your motor works, check this site out.
So first of all here is a crash course, not a lot of detail, on how the most common engines work.
The most familiar internal-combustion engines are piston gasoline engines used in most automobiles. In an
engine, the cylinder is housed inside an engine block strong enough to contain the explosions of fuel. Inside
the cylinder is a piston that fits the cylinder precisely. Pistons generally are dome-shaped on top, and
hollow at the bottom. In a four-stroke engine, the piston completes one up-and-down cycle in four strokes:
intake, compression, power, and exhaust. The Diesel Engine Works in a similar way but does not rely
on an ignition system like gasoline has.
The first stroke, the intake stroke, begins when the piston is at the top of the cylinder, called the cylinder
head. As it is drawn down, it causes a vacuum in the cylinder because the piston and the cylinder
form an airtight space. This vacuum helps to draw the fuel-air mixture into the cylinder through an open
intake valve, which closes when the piston reaches the bottom of the cylinder.
On the next stroke, called the compression stroke, the piston is pushed up inside the cylinder, compressing
or squeezing the fuel-air mixture into a tighter and tighter space. The compression of the mixture against
the top of the cylinder causes the air/mixture to heat up. Compressing the fuel-air
mixture also makes it easier to ignite and makes the resulting explosion more powerful. There is little space
for the expanding gases of the explosion to flow, which means they will push harder against the piston in
order to escape.
At the top of the compression stroke, the fuel-air mixture is ignited by a spark from a spark plug installed in
the cylinder head, causing an explosion that pushes the piston down. This stroke is called the power stroke
and this is the stroke that turns the crankshaft. The actual time that the Spark plug ignites the fuel-air mixture will vary a little from engine to engine but is generally 15-18 degrees BTDC (Before Top Dead Center) Where as in a Diesel engine the heat of the compressing fuel-air mixture and the time during the Combustion stroke that the fuel is injected is what starts the Combustion Stroke.
The final stroke, the exhaust stroke, takes the piston upward again, expelling the exhaust gases created by
the explosion from the cylinder through an exhaust valve. When the piston reaches the top of the cylinder,
it begins the four-step process again.
There are two principal types of Gasoline Engines. Motors that are Carbureted and motors that are fuel injected.
Most of all vehicles after the mid 1980?s are Fuel injected. Most of those before the mid 1980s are carbureted.
Carbureted engines mix the Fuel and air as it enters the engine through the intake manifold on the top of the
Engine. One will notice the presence of the carburetor on the intake manifold. Ordiniraly the fuel-air mixture is set with a adjustment screw located on the carburetor and will not vary due to the signals from any sensors that the vehicle may have.
There are two categories of Fuel Injected Vehicles ; Throttle Body Injection and Direct Port Injection, and both types rely on signals from the various sensors in the vehicle for delivery of a specific amount of fuel to acuretly achieve a Fuel-air mixture of 14.7:1, 14.7 parts air to each 1 part fuel, which is the most effective mixture for the engine.
Throttle body injection uses one or two fuel injectors located in the throttle body of the air intake.
According to the various sensor signals received by the Vehicles ECU, a Pulsed signal is sent to the Fuel
Injector to release fuel into the stream of air entering the intake manifold of the engine to complete
Combustion in the cylinder. The cycle of this signal (on time versus off time) does determine how much
Fuel is delivered to the engine.
Direct port injection will be most of the of systems you will find and they work on a similar principle, but
The fuel injectors release the fuel directly into the cylinder for the most effitive distribution of fuel. Direct
Port injected vehicles will have a fuel injector for every cylinder. Each injector will open and close once
Per combustion stroke, and the amount of time open determines the amount of fuel released into the
There are sensors that affect the amount of fuel that the engine mixes with the air to achieve
The most efficient fuel burn. The MAF Sensor, the MAP Sensor, the 02 Sensor, Air intake Temperature
Sensor all aid in determinating the amount of fuel the engine will mix with the incoming air but the sensors that
We will talk about are the MAP or MAF sensor and the 02 Sensor.
The job of the MAP/MAF sensor is the same but they go about it in two different ways. Their job is
Basically to tell the computer how much air is flowing into the engine. This information is used to calculate how much
Fuel is required for that amount of air. The MAP/MAF sensor is the “starting point” for the air
Fuel mixture. If the MAP/MAF sensor tells the computer that “X” amount of air is coming into the engine,
Then it needs to add “Y” amount of fuel to achieve “about” a 14.7:1 air fuel mixture. The 02 Sensor then fine tunes
Soon we will look into the adding of a hydrogen suplement and how it effects the performance of your vehicle.