Engine Basics And More!!

[cyberdoc95]

[SIZE=3]IGNITION SYSTEM [/SIZE]con't

The Coil
The coil is the device that generates the high voltages required to create a spark. It is a simple device -- essentially a high-voltage transformer made up of two coils of wire. One coil of wire is called the primary coil. Wrapped around it is the secondary coil. The secondary coil normally has hundreds of times more turns of wire than the primary coil.

Current flows from the battery through the primary winding of the coil.

The primary coil's current can be suddenly disrupted by the breaker points, or by a solid-state device in an electronic ignition.

If you think the coil looks like an electromagnet, you're right -- but it is also an inductor. The key to the coil's operation is what happens when the circuit is suddenly broken by the points. The magnetic field of the primary coil collapses rapidly. The secondary coil is engulfed by a powerful and changing magnetic field. This field induces a current in the coils -- a very high-voltage current (up to 100,000 volts) because of the number of coils in the secondary winding. The secondary coil feeds this voltage to the distributor via a very well insulated, high-voltage wire.

[cyberdoc95]

[SIZE=3]HOW CAMSHAFT WORKS[/SIZE]

The camshaft uses lobes (called cams) that push against the valves to open them as the camshaft rotates; springs on the valves return them to their closed position. This is a critical job, and can have a great impact on an engine's performance at different speeds. On the next page of this article you can see the animation we built to really show you the difference between a performance camshaft and a standard one.



Lobes are Key
The key parts of any camshaft are the lobes. As the camshaft spins, the lobes open and close the intake and exhaust valves in time with the motion of the piston. It turns out that there is a direct relationship between the shape of the cam lobes and the way the engine performs in different speed ranges.

To understand why this is the case, imagine that we are running an engine extremely slowly -- at just 10 or 20 revolutions per minute (RPM) -- so that it takes the piston a couple of seconds to complete a cycle. It would be impossible to actually run a normal engine this slowly, but let's imagine that we could. At this slow speed, we would want cam lobes shaped so that:

* Just as the piston starts moving downward in the intake stroke (called top dead center, or TDC), the intake valve would open. The intake valve would close right as the piston bottoms out.

* The exhaust valve would open right as the piston bottoms out (called bottom dead center, or BDC) at the end of the combustion stroke, and would close as the piston completes the exhaust stroke.

[cyberdoc95]

[SIZE=3]HOW CAMSHAFT WORKS[/SIZE] cont

Camshaft Arrangements
There are several different arrangements of camshafts on engines. We'll talk about some of the most common ones. You've probably heard the terminology:

* Single overhead cam (SOHC)
* Double overhead cam (DOHC)
* Pushrod

Single Overhead Cams
This arrangement denotes an engine with one cam per head. So if it is an inline 4-cylinder or inline 6-cylinder engine, it will have one cam; if it is a V-6 or V-8, it will have two cams (one for each head).

The cam actuates rocker arms that press down on the valves, opening them. Springs return the valves to their closed position. These springs have to be very strong because at high engine speeds, the valves are pushed down very quickly, and it is the springs that keep the valves in contact with the rocker arms. If the springs were not strong enough, the valves might come away from the rocker arms and snap back. This is an undesirable situation that would result in extra wear on the cams and rocker arms.

On single and double overhead cam engines, the cams are driven by the crankshaft, via either a belt or chain called the timing belt or timing chain. These belts and chains need to be replaced or adjusted at regular intervals. If a timing belt breaks, the cam will stop spinning and the piston could hit the open valves.


Double Overhead Cam
A double overhead cam engine has two cams per head. So inline engines have two cams, and V engines have four. Usually, double overhead cams are used on engines with four or more valves per cylinder -- a single camshaft simply cannot fit enough cam lobes to actuate all of those valves.

The main reason to use double overhead cams is to allow for more intake and exhaust valves. More valves means that intake and exhaust gases can flow more freely because there are more openings for them to flow through. This increases the power of the engine.

Pushrod Engines
Like SOHC and DOHC engines, the valves in a pushrod engine are located in the head, above the cylinder. The key difference is that the camshaft on a pushrod engine is inside the engine block, rather than in the head.

The cam actuates long rods that go up through the block and into the head to move the rockers. These long rods add mass to the system, which increases the load on the valve springs. This can limit the speed of pushrod engines; the overhead camshaft, which eliminates the pushrod from the system, is one of the engine technologies that made higher engine speeds possible.

The camshaft in a pushrod engine is often driven by gears or a short chain. Gear-drives are generally less prone to breakage than belt drives, which are often found in overhead cam engines.

[cyberdoc95]

[SIZE=3]HOW CAMSHAFT WORKS[/SIZE] cont

[SIZE=3]Variable Valve Timing[/SIZE]
There are a couple of novel ways by which carmakers vary the valve timing. One system used on some Honda engines is called VTEC.

VTEC (Variable Valve Timing and Lift Electronic Control) is an electronic and mechanical system in some Honda engines that allows the engine to have multiple camshafts. VTEC engines have an extra intake cam with its own rocker, which follows this cam. The profile on this cam keeps the intake valve open longer than the other cam profile. At low engine speeds, this rocker is not connected to any valves. At high engine speeds, a piston locks the extra rocker to the two rockers that control the two intake valves.

Some cars use a device that can advance the valve timing. This does not keep the valves open longer; instead, it opens them later and closes them later. This is done by rotating the camshaft ahead a few degrees. If the intake valves normally open at 10 degrees before top dead center (TDC) and close at 190 degrees after TDC, the total duration is 200 degrees. The opening and closing times can be shifted using a mechanism that rotates the cam ahead a little as it spins. So the valve might open at 10 degrees after TDC and close at 210 degrees after TDC. Closing the valve 20 degrees later is good, but it would be better to be able to increase the duration that the intake valve is open.



Ferrari has a really neat way of doing this. The camshafts on some Ferrari engines are cut with a three-dimensional profile that varies along the length of the cam lobe. At one end of the cam lobe is the least aggressive cam profile, and at the other end is the most aggressive. The shape of the cam smoothly blends these two profiles together. A mechanism can slide the whole camshaft laterally so that the valve engages different parts of the cam. The shaft still spins just like a regular camshaft -- but by gradually sliding the camshaft laterally as the engine speed and load increase, the valve timing can be optimized.

[ssaloon]

damn ang haba! you could've left the searching to us in the site ehehehe

for more, you can download the link found on the sticky thread "car hacks, mods for dummies" there's a link to a 380++ page PDF file on all sorts of stuff for your car ;)

[silhouette]

So informative!

[OTEP]

Pwede natin ilagay ito sa Tech Specs and Quick Reference section. :D

[yan_168]

di ba sa www.howstuffworks.com ito?

[cyberdoc95]

damn ang haba! you could've left the searching to us in the site ehehehe

for more, you can download the link found on the sticky thread "car hacks, mods for dummies" there's a link to a 380++ page PDF file on all sorts of stuff for your car

Hey Ssaloon,

Napagkatuwaan ko lang to put all these stuff together. That's self-teaching and learning, then, nababasa rin ng iba, right?!he he he..Yes, I could have left the searching to you and maybe, I'll just stop posting then.

Lately kasi, no new automotive-related topics have been posted. So I just took the initiative to put something that I could re-learn. Although not entirely new but at least something that you can learn from. Then, parang cumulative na knowledge lang na I could add something basic once a week or something until this will accumulate.

If you look at some of the topics posted on the Forum, its all about power, torque, problems about noisy engine sounds, engine designs,etc. With the basic knowledge about engine, you'll see that you can initially diagnose the problem yourself when you have the basic knowledge about the engine. This was what I was aiming to do..I bet, iilan lang siguro sa atin ang talagang alam ang lahat ng parte ng isang sasakyan by heart kundi siguro ang pagpa-load lang ng accessories. Not na there's anything wrong with that but at least hindi man lang maloko ng mga mekaniko na kung ano-ano na ang sinasabi kung nasisira ang sasakyan.

But I think nobody seems to appreciate the effort. Sayang lang din pala time ko nito. Why did I even bother in the first place... he he he...

Ssaloon, Thanks though for pointing that out to me...

Yes Yan168, If you have read from the beginning of this thread, I stated that my source is HOWSTUFFWORKS.COM and as a researcher in the medical field, I always state my source in any claim I have to make them all credible..Thanks for that comment...Really appreciate it.

To THE MODS: KINDLY CLOSE THIS THREAD. THANKS PO!

[gearspeed]

Sa totoo lang kaunti lang alam ko dyan mabasa nga yan mamaya..

[BlueBimmer]

andami hehe :puyat:

[ILuvDetailing]

Wow... I'l read this later.

[cyberdoc95]

[SIZE=3]CAR ENGINE COOLING SYSTEM BASICS[/SIZE]

Although gasoline engines have improved a lot, they are still not very efficient at turning chemical energy into mechanical power. Most of the energy in the gasoline (perhaps 70%) is converted into heat, and it is the job of the cooling system to take care of that heat. In fact, the cooling system on a car driving down the freeway dissipates enough heat to heat two average-sized houses! The primary job of the cooling system is to keep the engine from overheating by transferring this heat to the air, but the cooling system also has several other important jobs.

The engine in your car runs best at a fairly high temperature. When the engine is cold, components wear out faster, and the engine is less efficient and emits more pollution. So another important job of the cooling system is to allow the engine to heat up as quickly as possible, and then to keep the engine at a constant temperature.


[SIZE=3]The Basics[/SIZE]
Inside your car's engine, fuel is constantly burning. A lot of the heat from this combustion goes right out the exhaust system, but some of it soaks into the engine, heating it up. The engine runs best when its coolant is about 200 degrees Fahrenheit (93 degrees Celsius). At this temperature:

* The combustion chamber is hot enough to completely vaporize the fuel, providing better combustion and reducing emissions.
* The oil used to lubricate the engine has a lower viscosity (it is thinner), so the engine parts move more freely and the engine wastes less power moving its own components around.
* Metal parts wear less.

There are two types of cooling systems found on cars: liquid-cooled and air-cooled.

Liquid Cooling
The cooling system on liquid-cooled cars circulates a fluid through pipes and passageways in the engine. As this liquid passes through the hot engine it absorbs heat, cooling the engine. After the fluid leaves the engine, it passes through a heat exchanger, or radiator, which transfers the heat from the fluid to the air blowing through the exchanger.

Air Cooling
Some older cars, and very few modern cars, are air-cooled. Instead of circulating fluid through the engine, the engine block is covered in aluminum fins that conduct the heat away from the cylinder. A powerful fan forces air over these fins, which cools the engine by transferring the heat to the air.

[cyberdoc95]

[SIZE=3]CAR COOLING SYSTEM Cont[/SIZE]

Plumbing
The cooling system in your car has a lot of plumbing. We'll start at the pump and work our way through the system, and in the next sections we'll talk about each part of the system in more detail.

The pump sends the fluid into the engine block, where it makes its way through passages in the engine around the cylinders. Then it returns through the cylinder head of the engine. The thermostat is located where the fluid leaves the engine. The plumbing around the thermostat sends the fluid back to the pump directly if the thermostat is closed. If it is open, the fluid goes through the radiator first and then back to the pump.

There is also a separate circuit for the heating system. This circuit takes fluid from the cylinder head and passes it through a heater core and then back to the pump.

On cars with automatic transmissions, there is normally also a separate circuit for cooling the transmission fluid built into the radiator. The oil from the transmission is pumped by the transmission through a second heat exchanger inside the radiator.

Fluid
Cars operate in a wide variety of temperatures, from well below freezing to well over 100 F (38 C). So whatever fluid is used to cool the engine has to have a very low freezing point, a high boiling point, and it has to have the capacity to hold a lot of heat.

Water is one of the most effective fluids for holding heat, but water freezes at too high a temperature to be used in car engines. The fluid that most cars use is a mixture of water and ethylene glycol (C2H6O2), also known as antifreeze. By adding ethylene glycol to water, the boiling and freezing points are improved significantly.

[cyberdoc95]

[SIZE=3]CAR COOLING SYSTEM [/SIZE]cont

Water Pump
The water pump is a simple centrifugal pump driven by a belt connected to the crankshaft of the engine. The pump circulates fluid whenever the engine is running.

The water pump uses centrifugal force to send fluid to the outside while it spins, causing fluid to be drawn from the center continuously. The inlet to the pump is located near the center so that fluid returning from the radiator hits the pump vanes. The pump vanes fling the fluid to the outside of the pump, where it can enter the engine.

The fluid leaving the pump flows first through the engine block and cylinder head, then into the radiator and finally back to the pump.

[SIZE=3]CLICK ME TO VIEW A VIDEO ABOUT CAR COOLING SYSTEM!!![/SIZE]

Engine
The engine block and cylinder head have many passageways cast or machined in them to allow for fluid flow. These passageways direct the coolant to the most critical areas of the engine.

Note that the walls of the cylinder are quite thin, and that the engine block is mostly hollow.

Temperatures in the combustion chamber of the engine can reach 4,500 F (2,500 C), so cooling the area around the cylinders is critical. Areas around the exhaust valves are especially crucial, and almost all of the space inside the cylinder head around the valves that is not needed for structure is filled with coolant. If the engine goes without cooling for very long, it can seize. When this happens, the metal has actually gotten hot enough for the piston to weld itself to the cylinder. This usually means the complete destruction of the engine.

One interesting way to reduce the demands on the cooling system is to reduce the amount of heat that is transferred from the combustion chamber to the metal parts of the engine. Some engines do this by coating the inside of the top of the cylinder head with a thin layer of ceramic. Ceramic is a poor conductor of heat, so less heat is conducted through to the metal and more passes out of the exhaust.

[ILuvDetailing]

Mods paki sticky naman to...

[cyberdoc95]

[SIZE=3]CAR COOLING SYSTEM[/SIZE] cont

Radiator
A radiator is a type of heat exchanger. It is designed to transfer heat from the hot coolant that flows through it to the air blown through it by the fan.

Most modern cars use aluminum radiators. These radiators are made by brazing thin aluminum fins to flattened aluminum tubes. The coolant flows from the inlet to the outlet through many tubes mounted in a parallel arrangement. The fins conduct the heat from the tubes and transfer it to the air flowing through the radiator.

The tubes sometimes have a type of fin inserted into them called a turbulator, which increases the turbulence of the fluid flowing through the tubes. If the fluid flowed very smoothly through the tubes, only the fluid actually touching the tubes would be cooled directly. The amount of heat transferred to the tubes from the fluid running through them depends on the difference in temperature between the tube and the fluid touching it. So if the fluid that is in contact with the tube cools down quickly, less heat will be transferred. By creating turbulence inside the tube, all of the fluid mixes together, keeping the temperature of the fluid touching the tubes up so that more heat can be extracted, and all of the fluid inside the tube is used effectively.


Radiators usually have a tank on each side, and inside the tank is a transmission cooler. In the picture above, you can see the inlet and outlet where the oil from the transmission enters the cooler. The transmission cooler is like a radiator within a radiator, except instead of exchanging heat with the air, the oil exchanges heat with the coolant in the radiator.


Pressure Cap
The radiator cap actually increases the boiling point of your coolant by about 45 F (25 C). How does this simple cap do this? The same way a pressure cooker increases the boiling temperature of water. The cap is actually a pressure release valve, and on cars it is usually set to 15 psi. The boiling point of water increases when the water is placed under pressure.



When the fluid in the cooling system heats up, it expands, causing the pressure to build up. The cap is the only place where this pressure can escape, so the setting of the spring on the cap determines the maximum pressure in the cooling system. When the pressure reaches 15 psi, the pressure pushes the valve open, allowing coolant to escape from the cooling system. This coolant flows through the overflow tube into the bottom of the overflow tank. This arrangement keeps air out of the system. When the radiator cools back down, a vacuum is created in the cooling system that pulls open another spring loaded valve, sucking water back in from the bottom of the overflow tank to replace the water that was expelled.

[cyberdoc95]

[SIZE=3]CAR COOLING SYSTEM[/SIZE] con't

Fan
Like the thermostat, the cooling fan has to be controlled so that it allows the engine to maintain a constant temperature.

Front-wheel drive cars have electric fans because the engine is usually mounted transversely, meaning the output of the engine points toward the side of the car. The fans are controlled either with a thermostatic switch or by the engine computer, and they turn on when the temperature of the coolant goes above a set point. They turn back off when the temperature drops below that point.

Rear-wheel drive cars with longitudinal engines usually have engine-driven cooling fans. These fans have a thermostatically controlled viscous clutch. This clutch is positioned at the hub of the fan, in the airflow coming through the radiator. This special viscous clutch is much like the viscous coupling sometimes found in all-wheel drive cars.

[the_wildthing]

Suggestion ko lang is always go to www.howstuffworks.com, kasi minsan may updates...

[Marc MD]

ok ito!! dadami na naman ang knowledge ko para makagawa ng sariling DIY's!!