Engine Stuff

Every vehicle is equipped with an engine, it makes the car run. There are a multitude of different engines being used in the automotive industry today. They are classified by the number of cylinders (4,5,6,8,10 or 12) the way in which the cylinders are arranged, the type of valve train, and ignition type. An engine could be In-Line (cylinders arranged in a row) V type (cylinders in two rows resembling a V) slant (the entire engine block is slanted) or opposed (the cylinders are in two rows but instead of making a V shape they are opposite the crankshaft.) An engines valve train can be configured a few different ways, overhead camshaft, overhead valve or dual overhead cam. There are only two types of ignition systems, spark and compression. Gasoline engines have spark ignitions, in contrast a diesel engine uses compression, both are considered internal combustion engines because the combustion occurs inside the engine.



Four stroke engines are the most common, the strokes are intake, compression, power or combustion and exhaust. They need four basic things to run air, spark, fuel and compression. Each element combined creates an explosion inside the combustion chamber, the space in between the top of the cylinder and piston. During the intake stroke the piston is moving downward and the intake valve is opened creating a vacuum for the air/fuel mixture. When the intake valve closes and the piston begins to move up compressing the two substances, the engines compression stroke is taking place. The combustion stroke is when the compressed mixture is ignited by the engines spark plug, and the exhaust stroke is when the piston moves down a second time from the pressure of the explosion and the exhaust valve is opened. As the piston is forced downward it rotates another component called the crankshaft. The piston is connected to a rod, which attaches to the crankshaft. One end of the crankshaft is attached to the flywheel, sending the power of the engine to the wheels of the vehicle. The camshaft (smaller then the crankshaft) controls the vales mentioned above with lobes. It is driven by the crankshaft.


The engine components can not rub against one another, as that would create friction, and metal shavings to be distributed throughout the engine. If an engine is dry it will sieze up, and the vehcile will be unable to run. This is why oil is used as a lubricant, and why it has to be changed regularly, without it an engine wouldn't last. The oil can be 5w-30, 10w-20, 10w-3o and many other viscosity levels.


There are various tests preformed to check an engines condition. A compression gauge will check compression in any given cylinder. Poor compression will result in a loss of power, and a poorly running engine. A cylinder power balance test is used to make sure all the cylinders are producing the same output. To preform this test a cylinders spark plug is shorted, and the engine speed drop is recorded. A technician can also test the vacuum produced with a vacuum gauge. Scan tools have also proven helpful when identifying engine problems. They can read and clear trouble codes which set MIL (malfunction Indicator Light) lights or check engine lights. Engines are a very complex and essential component of any automobile.

I was bored...

Brake Overview, for those interested

A brake system is arguably one of the most important systems in a vehicle. It is a hydraulic system that transfers the pressure of the drivers foot against the pedal to the wheels of the vehicle. Cars originally only had one system, meaning if there was a problem with the brakes the driver would be unable to stop. In the late sixties (1967) a federal law was passed requiring all automobiles to be equipped with two brake systems. If one system had a problem the driver would still have some braking power. There are two types of dual systems, one is a front/rear split and the other is diagonal. The front/rear split is not as effective as the diagonal split. It's lines are divided between the front two wheels and the back two. The problem with that is the front brakes do approximately seventy percent of the breaking on a vehicle, so if a vehicles front brakes went, the driver would only have about thirty percent of his or her breaking power. A diagonal system includes one front and one rear wheel, so if a system has a problem the driver will have half the breaking power.
The system utilizes hydraulics and leverage. It takes a large amount of force to stop a vehicle, therefore the pressure applied by the driver has to be multiplied. The master cylinder converts the motion of the pedal being pressed into hydraulic pressure. It contains two pistons, each for one half of the system. As the brake pedal is depressed the master cylinder's piston assembly shifts, applying pressure to fluid, which travels out through ports. The fluid then enters the brake lines, usually made of steel and copper. When the fluid reaches the wheel cylinder, pistons are pushed outward forcing the brake shoes or pads to contact the drum or rotor. Most vehciles have discs in the front and drums in the rear, however four wheel discs do exist. I was bored, and couldn't sleep :-P

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