Monthly Archives: July 2010

How A Car Engine Works – Part 2

While the cylinders are the core of the car engine (see How A Car Engine Works – Part 1) , there are a number of peripheral systems that are necessary for them to continue functioning.

Let’s start by looking at a few parts of the cylinder in greater detail.

Intake and exhaust camshafts

In order for the cylinder to operate correctly, the valves need to open and close at the right moments. Timing is everything; all of the parts of the cylinder (valves, piston, spark plug, etc.) need to be in sync with one another.

The camshafts regulate the opening and closing of the valves. Each camshaft is a circular rod that turns as the crankshaft does. The two shafts are connected by a timing belt that ensures their movements are coordinated.  As you can see in the diagram, the camshaft has lobes on it; as the camshaft turns, each lobe will briefly push the valve open. After the lobe has passed over the valve, the valve closes again. Linking this process to the motion of the crankshaft ensures that the valves open when the piston is at the correct point in the cycle.

Spark plug

First, the spark plug requires electrical input in order to generate the spark that ignites the compressed gas in the cylinder. This energy comes from the car’s twelve volt battery. This battery powers all of the other electrical systems in the car as well, such as the radio, the lights, power windows, and the starting system, which I’ll discuss below. The battery is connected to an alternator. A belt connects the alternator to the engine, so that as the engine spins, the belt also spins, generating energy to recharge the battery. This is why car batteries don’t run out, the way a normal battery would, unless the battery is old or defective, or electrical systems (like the headlights) are left on when the engine isn’t running.

Next, the spark plug needs to ignite at the right moment in the four-stroke cycle in order for combustion to occur. This timing is regulated by the distributor. A distributor receives power from the ignition system coil; this is basically a high-voltage transformer. The distributor consists of two parts: the rotor and the cap. The cap is attached to the ignition wires, which lead to the spark plugs. If a car has six cylinders, a distributor will have six ignition wires, one connected to each spark plug. The rotor is connected to the ignition system coil and sits in the center of the cap. As the camshaft turns, the rotor also turns so that each ignition wire is briefly connected to the power source. As a result, the spark plugs fire one at a time; this results in smoother motion. If cylinders fired in groups, the car’s forward movement would be uneven.

 What else needs to happen in order for the engine to function?

First, air needs to flow into the cylinders. In normally aspirated engines, the air flows through an air filter and directly into the cylinder. In high-performance turbo-charged or super-charged engines, however, the air is pressurized first. This means that more of the air and fuel mixture can be crammed into each cylinder, creating more energy during the combustion process.

The fuel for the air and fuel mixture is provided by the fuel system. First, a pump draws the gasoline up from the tank. Next, this fuel is either mixed with air by a carburetor, or, in a fuel-injected engine, is injected directly into the cylinder itself.

As you’d expected, this process produces a lot of heat. In order to keep the engine from overheating and melting, a cooling system needs to be in place. Most modern cars are water cooled, although some older models (such as the VW Beetle) are air cooled. In a water-cooled car, a water pump circulates water through a “jacket” of pipes around the cylinder. This water then passes through the radiator, where it is cooled off before being re-circulated. Without enough water, the system won’t function. This is why it’s important to check water and oil levels regularly!

The car engine also contains a lot of moving parts. For these to move smoothly, they need to be lubricated with oil. Otherwise, moving parts would grind one another down or stick altogether. This results in a less efficient, damaged, or totally non-functioning engine. The lubrication system ensures that oil gets to all parts that need it. The oil pump draws oil out of the sump. It moves through the oil filter, to remove any dirt that could clog the engine. Next, it is squirted onto the parts that need it, in particular the walls of the cylinder and the bearings on the shafts. The oil eventually trickles back down into the sump, and is taken up into the pump again.

Once exhaust leaves the cylinder, it passes into the exhaust system. In this system, the exhaust exits the car through the tail pipe. If this were all there were to an exhaust system, however, most cars would create far too much noise and air pollution.

For this reason, most cars have mufflers, which dampen the sound of all the small explosions occurring in the engine. Modern cars also have an emissions control system. Before leaving the car, exhaust will pass through a catalytic converter. Most catalytic converters have three stages; in the first two stages, the exhaust passes over different kinds of metal which act as catalysts to either reduce or oxidize one of the poisonous components of the exhaust. The third stage contains a sensor, which monitors the level of oxygen in the exhaust. This sensor communicates with a computer, which can then adjust the fuel-air ratio reaching the engine, in order to ensure that the engine is operating as efficiently as possible.

Last, but definitely not least, is the car’s starting system. As I mentioned in part one, the four-stroke process is self-sustaining once you’ve gotten it going. However, in order to get this process going, you need to start turning the crankshaft. This means overcoming all of the internal friction and pressure in the cylinders, providing enough energy to open and close the valves, and powering the various pumps and other equipment necessary for engine function.

The power for all of this is provided by the starting motor, a separate, electrically powered motor that turns the crankshaft a few times to get the four-stroke cycle started. This system is activated by a starting solenoid.

With all of these intricate moving parts and inter-dependent systems, it’s amazing that car engines can last as long as they do—and don’t break down more often! However, in my next entry, I’ll explore some of the most common problems that can occur in engines, how to diagnose these problems, and what basic maintenance you should do to prevent problems from happening in the first place.

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How A Car Engine Works- Part 1

The car engine is the heart—or perhaps rather the stomach—of the car. In the engine, gasoline is burned to produce energy; this energy is then converted into motion. An engine has a number of components that work together to ensure this intricate piece of machinery continues to function smoothly.

First, there are the cylinders, in which gasoline is converted into energy, which is then harnessed to move the car.

Next, there are the valve train, which regulates the intake of fuel and the output of exhaust, and the ignition system, which insures that the spark plugs ignite the fuel in the cylinders at the correct time.

Engines also have a starting system, which consists of a separate, electric powered motor that is used to get the car going.

The cooling, exhaust, lubrication, and fuel systems respectively make sure that the engine doesn’t overheat; exhaust is filtered and released; all parts receive necessary oil; and the proper fuel mixture is injected into the engine.

Let’s start with the cylinders.

Basically, a car engine is a kind of internal combustion engine. This essentially means that a fuel-air mixture is burnt inside a closed chamber in order to produce mechanical motion. In a car, this process occurs inside a cylinder.

You may have heard of “V6” engines. This refers to the number of cylinders contained in the car engine; in a “V6” engine, there are six cylinders that are arranged in a “V” configuration, with three on each side. Historically, American automakers have tended to prefer V6 engines. However, Japanese makers began using highly efficient 4-cylinder engines in the 80s and 90s; these engines are often more fuel-efficient and produce lower Carbon emissions. V6 and four-cylinder engines both have pros and cons, which are worth considering when buying a car.

Now, let’s take a look within an individual cylinder. A cylinder is a sealed system that has a number of moving parts that are kept well lubricated with oil. Before we look at the actual combustion process, let’s take a moment to identify some of the key components of the cylinder. Here is a diagram of an engine cylinder, pictured at each of the four points in the combustion cycle (more on this later):

 

The exhaust and intake camshafts are the two ovaloid shapes at the top of the cylinder. They regulate the opening of the valves.

The valves are the two plugs below the camshafts. They open to allow fuel in or exhaust out; they close to seal the chamber during combustion.

The spark plug is the coil located between the two valves. The spark plug ignites the fuel-air mixture.

The piston, the square, olive-colored part in the middle of the cylinder, moves up and down in the cylinder to compress the fuel-air mixture and move the crankshaft.

The piston rings (not pictured) create a seal between the piston and the cylinder. This prevents fuel from leaking out of the chamber and oil from seeping in.

The crankshaft, pictured in cross section at the bottom of the image, is a rotating shaft that converts the piston’s vertical motion into the circular motion the car needs to move forward.

The sump (not pictured) contains the oil that lubricates the system. It surrounds the crankshaft.

To power the car, these parts work together in a four-stroke combustion process. This is also known as the Otto cycle, after the German engineer Nicolaus Otto, who built the first car with this kind of engine in the 19th century (an interesting story for another day!)

This process occurs in four steps, or strokes: the intake stroke, compression stroke, combustion stroke, and exhaust stroke. First, remember that the crankshaft is turning throughout this cycle in order to move the piston up and down. Each of these four points in the cycle is illustrated in the image of the cylinder above.

INTAKE STROKE (I) —the intake valve opens. The piston moves down to allow the air and fuel mixture to fill the cylinder. The intake valve then closes, sealing the system.

COMPRESSION STROKE (II) —the piston moves back up to compress the fuel and air mixture in the sealed chamber. This increases the power of the combustion.

COMBUSTION STROKE (III) —a spark from the spark plug ignites the fuel and air mixture. Rather than “exploding” outright, the mixture burns. This causes the mixture to expand rapidly as gases are produced and heated. Since the chamber is sealed, the expansion of the mixture forces the piston down.

EXHAUST STROKE (IV) —once the piston reaches the bottom of the cylinder, the exhaust valve opens to release the exhaust, i.e. the “leftover” gases that remain in the cylinder after combustion is finished.

In a car engine, the cylinders work on staggered cycles. Basically, while half of the pistons are moving on a downward stroke, the other half are moving upwards. Since all cylinders are connected to the same crankshaft, the downward stroke of half the cylinders powers the upward stroke of the other half, and vice versa. Therefore, once the system gets going, it becomes self-sustaining.

So just how does the system get started? That depends on the starter system, which I’ll explain, along with the other components of the engine, in part two.

To learn more about this topic, or a broad range of subjects from “How To Change A Tire” to “How To Jumpstart Your Car”, visit DefensiveDriving.com’s Safe Driver Resources website!

 Check out these sites for more information about online defensive driving in Texas, online defensive driving in Florida, and business driver safety.

Car Basics For Dummies

This entry marks the start of a new series on the basics of how cars work. Now, I drove for a long time before I learned how an engine works. Phrases like “blew a gasket” and “torque converter” might as well have been old Icelandic sayings. Looking under the hood of my car felt a bit like looking at a bird’s nest or a Rorschach blot: oh, that’s interesting …I wonder what that could be?

Why did I never bother learning about cars? First, no one in my family is really a “car person,” so I didn’t have a parent or older sibling who could teach me. Second, the mechanical complexity of a car seemed both boring and intimidating. Finally, it just didn’t seem important.

Now that I am a more enlightened driver, however, I realize that knowing about how a car works is worth the bit of effort and time it may take to understand some of the mechanics. Even those of us with only the haziest recollections of high school physics can still grasp the fundamentals of how a car functions. Knowing this not only gives you a greater appreciation for the mechanical marvels contained in your car, but also equips you with basic vocabulary and diagnostic tools that will come in handy should something go wrong with your car. Having a greater awareness of how my car works also helps me to take better care of my car and to be a better driver. I feel more secure behind the wheel now that my car seems more like a mechanical marvel and less like a complete mystery.

In the following series of posts, I’ll explore, in very basic terms, the rudimentary functions of an average car. These entries are designed for those with little or no mechanical expertise and knowledge of cars. I’ll follow up each explanatory post with one about basic maintenance and common problems associated with that car part. As it stands now, this series will cover the following areas:

Engine – Part 1 and Part 2

Transmission—manual and automatic

Drive train—brakes,( Part 1 – Braking Basics;  Part 2 –  Disc and Drum; Part 3 – Power and Antilock),  differentials, tires, steering (Part 1 and Part 2)

Accessories—heating and AC, fuel gauge and odometer, cruise control

If there’s a topic you’d particularly like to see featured that isn’t on this list, post a comment and I’ll see what I can do.

Hypermiling Basics

Hypermiling. The first time I heard the word, I imagined some strange engine malfunction, or perhaps a kind of car-induced anxiety attack, the automotive equivalent of hyperventilating. Of course, neither of these vague impressions was remotely correct. In reality, hypermiling is many things: extreme cost-cutting strategy, environmentally friendly practice, competitive sport, and 2008 Word of the Year (according to the New Oxford American Dictionary.)

Hypermiling is, in short, the pursuit of the maximum number of miles per gallon. Hypermilers aim to exceed the EPA miles-per-gallon rating of any given car. Hypermilers regularly practice many of the basic gas-conservation measures I described in my previous post on the subject; however, they also implement an array of advanced techniques that can result in amazing gas savings. Experienced hypermilers regularly achieve over 100 MPG (when driving Hybrids.) For example, at the 2006 Hybridfest MPG Challenge in Madison, Wisconsin, the winning driver (Wayne Gerdes) averaged 183 MPG over the assigned route.

Some critics, including the American Automobile Association, have argued that hypermiling practices can be dangerous and, in some cases, illegal (overinflating tires and coasting with the engine off are two examples often cited in this debate.) In response, hypermiling associations have argued that true hypermilers would never endorse an illegal practice and that, in fact, hypermilers are more conscientious about practicing safe driving measures often ignored by others, such as paying detailed attention to their surroundings, anticipating traffic hazards, and driving at or below posted speed limits.

Like many things, hypermiling practices are tools, which can be used to good and bad effect. In this post, I’ll describe a few of the most common hypermiling measures, although dozens, if not hundreds, more exist. Bear in mind that a journey of a thousand miles begins with a single step. You won’t be able to achieve 100 MPG (or more) overnight; many of these techniques take some time and practice to adjust to. Experienced hypermilers recommend adding techniques to your toolbox one at a time, and testing them out first in an empty parking lot or other safe practice area. When sharing a road with others, don’t ever attempt maneuvers that you don’t feel 100% comfortable executing.

EQUIPMENT

Obviously, the kind of car you drive will have a huge impact on the MPG you can achieve. Hybrids, such as the Honda Insight or Toyota Prius, are far more fuel-efficient than the average car. Watch out for an upcoming entry on purchasing, owning, and driving a hybrid, and entries on other types of fuel-efficient technologies (such as bio-diesel.) However, many of these hypermiling techniques will also produce noticeable increases in fuel efficiency in “normal” cars.

Driving a manual transmission, rather than automatic transmission, can also aid hypermiling. The greater control over the car that manual transmission gives you makes many hypermiling maneuvers, such as coasting, easier.

Finally, consider investing in an Instantaneous Fuel Consumption Display (unless you drive a car, like the Toyota Prius, that comes equipped with such a device.) There are a number of different kinds of devices that can be used to monitor fuel consumption; you may want to speak to your mechanic about which would best suit your budget and model of car. Having such a device is perhaps one of the best ways to train yourself to be a more efficient driver, as you can easily see the results of different techniques as you apply them.

EIGHT KEY STRATEGIES

First and foremost, hypermiling begins with basic fuel economy strategies: avoid sudden braking and acceleration, avoid unnecessary idling, try not to drive in heavy traffic, use air condition sparingly, combine several short trips into one longer one, and don’t drive too fast.

However, hypermilers go above and beyond these basic common sense tenets with a number of advanced maneuvers:

1.      Ridge Riding

This is a way of avoiding the “drag” caused when water or snow accumulates in the troughs worn into the lanes on the road. Basically, most drivers drive in the center of the lane, which produces uneven wear on the pavement, creating ridges and troughs. (These depressions are slight but can have a noticeable impact.) Instead of driving in these slight depressions, drive on the “ridges” on either side, so that the car has one wheel on the center ridge and the other on the ridge on the right or left side of lane. According to some hypermiling proponents, this technique has the added safety benefit of causing other drivers to take notice of your unusual positioning in the lane, and hence they will drive with greater awareness.

2.      Anticipate Potential Obstacles

Driving at a steady speed, without stopping or accelerating, is a great way to increase gas mileage, as acceleration burns excess gas. For this reason, hypermilers maintain an awareness of road conditions in the distance, so that they can anticipate and avoid potential obstacles in order to maintain a constant speed.

3.      Driving With Load (DWL)

Essentially, driving with load means maintaining a constant fuel consumption rate as you pass over hilly terrain. Say you have cruise control set. Cruise control keeps your car at a constant speed; however, this means that your engine has to exert more power to maintain this speed when you are going up a hill. In  DWL, you maintain a constant fuel consumption instead of a constant speed. If you have an instantaneous fuel consumption display, you can use this device to make sure that you maintain constant fuel consumption. If you don’t have an IFCD, however, you can approximate constant fuel consumption by keeping the accelerator “locked” at a fixed angle as you move up and over the hill.

4.      Driving Without Brakes (DWB)

Basically, when driving in heavy traffic, pretend you don’t have brakes. Create a large buffer zone around your car, so that you have time to react to changes in traffic speed without actually having to stop. This can take some patience, especially as other cars will likely cut into your buffer space. However, this can ultimately be a safer and more relaxing way to drive in traffic. The goal is to achieve a constant slow speed despite the “stop and go” of cars around you.

5.      Smart Braking

When you brake, your brakes convert the kinetic energy of your moving car into heat, so that your car slows down. Essentially, braking is like “burning” up gasoline without making any forward progress. For this reason, hypermilers practice smart braking. First, anticipate lights; start slowing down way before the red light so that, ideally, you will still be moving when the light changes and the traffic moves forward again. The goal is to continue rolling without actually coming to a dead stop. (Remember, however, that rolling through stop signs is illegal. Safety and legality are still more important than fuel economy.)

If you are stopping on a downhill plane, try to stop some ways before the end of the hill so that you can use the slope to get your car rolling again without having to accelerate. If stopping near or on an uphill, try to roll as far up the hill as possible before coming to a complete stop, to avoid having to accelerate uphill.

6.      Rabbit Timing

This is related to smart braking and is a technique for maximizing fuel economy when driving near lights with motion sensors. If you see a red, yellow, or stale green light ahead, slow down and allow another car to pass you and “trip” the motion sensor, so that the light is green by the time you get there, and you can continue through without stopping.

7.      Smart Parking

Remember that your car is least fuel-efficient when the engine is cold. This means that you want to execute most of your parking maneuvers when the engine is warm. For this reason, reverse into parking spaces, so that you can easily pull away. If possible, seek out parking spaces on an incline, so that you will be able to roll out of the space, aiding your acceleration with a “cold” engine. Parking in the sun can also help to keep your engine warm and increase efficiency.

8.      Engine Off Coasting

This is the limit of my personal hypermiling comfort zone. When slowing down or moving downhill, some hypermilers recommend engine-off coasting as a means to boost efficiency. This involves shifting to neutral, turning off the engine by setting the ignition key to IG-I, then turning it back to IG-II to activate the electronics so that the steering wheel doesn’t lock. However, power steering and power braking functions are likely to be lost. This most easily practiced in a manual transmission car without power steering.

However, this is one of the “borderline” hypermiling techniques that can potentially be dangerous and even illegal in some places. If you drive a manual transmission car, coasting in neutral with the engine still running is a safer, albeit less fuel efficient, alternative.

These are a few basic strategies. However, there are dozens more. If you do catch the hypermiling bug, you may want to check out www.cleanMPG.com, which offers both introductions to hypermiling basics and forums for sharing more advanced tips, and www.ecomodder.com, which offers a comprehensive list of 100+ hypermiling tips.

Even if you don’t become a committed hypermiler, incorporating one or more of these techniques into your daily commute could still help you to conserve gas and save money.

To learn more about this topic, or a broad range of subjects from “How To Change A Tire” to “How To Jumpstart Your Car”, visit DefensiveDriving.com’s Safe Driver Resources website!

Check out these sites for more information about online defensive driving in Texas, online defensive driving in Florida, and business driver safety.