29 Aug Understanding The Inside of Your Car Engine
It’s helpful to have a good understanding of the parts making up a car engine.
Understanding the basics about your car engine will lessen any confusion the next time you talk with your mechanic.
Engine (or Cylinder) Block
If you’re wondering what an engine block is, well it actually forms the foundation of your vehicle’s engine. Most are made of an aluminum alloy, but some manufacturers still use iron. An engine block is sometimes called a “cylinder block” because there are cylinder tubes cast into the basic structure. This is where the pistons are situated and move up and down. When you increase the number of cylinders in a car engine, you make it more powerful. Aside from cylinders, there are a number of ducts and passages built into an engine block that allow coolant and oil to flow to specific parts throughout the engine.
The differences between a four cylinder, V6 and V8 Engines
Four cylinder engines typically mount the cylinders above the crankshaft in a straight line. This type of engine layout is referred to as an “inline engine.”
Another type of layout for four-cylinder engines is “the flat four” in which the cylinders are laid out horizontally in two different banks. The crankshaft is then placed down the center.
For engines with over four cylinders, there are two separate cylinder banks with three or more cylinders on each side. With the cylinders being divided into two separate banks, the engine itself is in the shape of a “V.” Therefore, a V-shaped engine that has six cylinders is called a “V6 engine.” So it stands to reason that an eight-cylinder car engine with four cylinders in each bank, would be called a “V8 engine.”
An engine’s combustion chamber is where all the action is. This is where the fuel combines with an electrical spark and air pressure to create an explosion. This is what causes the pistons to go up and down, which essentially creates the power needed to get the car moving. A combustion chamber consists of the cylinder itself, which acts as the wall, the piston, acting as the floor, and the cylinder head, which serves as the ceiling.
A cylinder head is basically just a piece of metal placed over the cylinders. To make sure there’s room enough for the combustion to take place at the top, there are little round indentations cast into the metal plate. To seal the joint along the cylinder block and cylinder head, a head gasket is used. Fuel injectors, spark plugs and valves (intake and outtake) are mounted onto the cylinder head.
Pistons look like soup cans placed upside down as they go up and down inside the cylinder. When fuel is ignited inside the combustion chamber, the piston is forced downward, which causes the crankshaft to move. A connecting rod (con rod) attaches the piston to the crankshaft by way of a piston pin, with the con rod connecting to the crankshaft by way of a con rod bearing.
At the very top of a piston, there are a few little grooves, three or four, cast right into the metal. The piston rings are placed inside these grooves. These rings are what actually touches the wall of the cylinder. Piston rings are made of iron and there are two different types: compression and oil rings. Compression rings are at the top and these press outward onto the cylinder walls to create a strong seal. Oil rings are at the bottom of the piston to prevent oil seeping out from the crankcase into the engine’s combustion chamber. The oil ring also swabs down the excess oil from the cylinder walls, sending it back to the crankcase.
The crankshaft can typically be found near the bottom of the engine block, fitting lengthwise. This is the mechanism that converts the pistons’ motions up and down into a rotational type of motion, which enables the vehicle to move. The crankshaft extends the length of the engine block. At the front end, it’s attached to rubber belts, which are connected to the camshaft and powers up other parts of the vehicle. At the back, the camshaft is attached to the drive train, which powers up the wheels. At both ends of the crankshaft there are oil seals (O-rings) preventing oil from seeping out.
You will find the crankshaft inside the engine’s crankcase, which is underneath the cylinder block and acts to protect and shield the crankshaft and its connecting rods from objects coming in from the outside. The oil pan is located at the base of the crankcase to store the engine’s oil. Within the oil pan is an oil pump used for pumping the oil through a filter, which then squirts onto the crankshaft, the con rod bearings, and the cylinder walls in an effort to lubricate the motion of the piston as it strikes. The oil will ultimately drip back down to collect in the oil pan, just to start the process all over again.
There are what’s called “balancing lobes” along the crankshaft, there to counterbalance the crankshaft and keep the engine safe from damage that could be caused by the wobbling that happens from the spinning of the crankshaft.
There are also main bearings along the crankshaft, which create a smooth surface in between the crankshaft itself, and the engine block, so the crankshaft can spin.
The camshaft is considered to be the engine’s brain. It works together with the crankshaft by way of a timing belt to ensure that the intake and outtake valves work properly, opening and closing at the right times for the engine to perform at its best. The timing of all this valve opening and closing is controlled by egg-shaped lobes extending across the camshaft.
In most cars, the camshaft extends through the top of the engine block, right above the crankshaft. On cars with inline engines, one camshaft controls the intake and outake valves. But on cars with V-shaped engines, there are two camshafts. One for controlling the valves situated on one side of the V with the other camshaft controlling the valves on the other side. There are certain V-shaped engines that come with two camshafts for each cylinder bank. It’s set up for one camshaft to control one side of valves, with the other camshaft controlling the other side.
The crankshaft and camshaft must move in coordination and they do this with a timing chain or belt. The timing chain or belt keeps both in the same position relative to each other, at all times when the engine is in operation. If somehow the crankshaft and camshaft got knocked out of sync then the car engine wouldn’t be able to work.
Valve Train (or Valvetrain)
This is a mechanical system mounted onto the cylinder head, responsible for controlling how the valves operate. The valve train system is made up of valves, pushrods, rocker arms, and lifters.
Valves come in two different types: intake and outtake valves. The intake valves’ job is to introduce a mixture of fuel and air into the engine’s combustion chamber, which leads to the combustion that powers the engine. The outtake valves release the exhaust resulting from the combustion so it escapes the combustion chamber.
The typical car will have just one intake and one outtake valve for each cylinder. But for most high-performing cars, there are four valves for each cylinder. These multi-valve systems enable the engine to “breath” more easily, and this improves the engine’s performance.
Rocker arms are the small levers touching the lobes on the camshaft. As a lobe lifts up one side of the rocker arm, the other side presses down onto the valve, causing it to open and let air come into the combustion chamber or to let the exhaust escape out. The rocker arms work somewhat like a playground see-saw.
Pushrods (or Lifters)
There are times when the camshaft lobes directly touch a rocker arm, which opens and closes the valve. But on a car engine with overhead valves, the lobes don’t directly contact the rocker arms, instead pushrods are used.
Three Fuel Injection Systems
To bring about the combustion necessary to get the pistons moving, there must be fuel brought into the cylinders. All cars today have one of three types of fuel injection systems:
- Direct fuel injection: has each cylinder getting its own injector. The injector squirts fuel right into the combustion chamber, timing it perfectly to create combustion.
- Ported fuel injection: works not by squirting fuel right into the cylinder, but by squirting it right into the intake manifold, which is outside near the valve. Then, as the valve opens, fuel and air enter into the combustion chamber.
- Throttle body fuel injection: operate similar to carburetors, but with no carburetor. In this system there is just one fuel injector, so each cylinder does not get its own. The injector squirts fuel into a throttle body where it mixes with air and is then distributed to the cylinders by way of the intake valves.
Each cylinder has a sparkplug above it. When a sparkplug goes off, the compressed air and fuel is ignited, which causes a tiny explosion that in turn thrusts the piston downward.
So now that we know all the basic parts of the engine, let’s take a look at the movement that actually makes our car move: the four-stroke cycle.