Auto questions: how brakes work

This brief summary will help you understan dyour braking system.
The braking system on a car is easily the most important safety feature. Over the years, these systems have been developed and refined by manufacturers to make them more dependable and effective in everyday driving. But how does the brake system work and enable a driver to press a pedal and retard a vehicle's speed?
The most common brake system used on modern passenger cars employs disk brakes on the front wheels and either drum or disk brakes on the rear. The disk or drum brakes are connected to the master cylinder through a closed network of hoses and lines usually constructed of reinforced rubber.
This closed network of lines forms a hydraulic system and is filled with brake fluid. When the brake pedal is depressed by the driver, a plunger or piston in the master cylinder is pushed down on, causing an increase in pressure throughout the entire hydraulic system as brake fluid (or any fluid for that matter) is not easily compressed. This is also the reason why the brake fluids in cars should be pure, as air bubbles and other impurities can be more easily compressed reducing the effectiveness and efficiency of the system.
As this hydraulic pressure created by the depressed brake pedal is transferred through the entire system of brake lines, it culminates at the braking unit located at each wheel. These braking units work by causing the brake pads/shoes to squeeze against the disc or drum when pressure is applied by a piston(s) at the end of the brake lines at each wheel. As the brake pads/shoes are constructed out of a very hard and rough material, the car’s speed is retarded as the pads/shoes create friction when dragged against the disk/drum. The result of this friction between the pad/shoe and disk/drum is the generation of heat which is the form of energy that the speed of the car is converted into.
This friction produced between the pads/shoes and the disk/drum is what causes these braking components to wear down over time and eventually need replacement. Excessive heat under continuous and prolonged braking (e.g. driving down a steep mountain road) is what causes 'brake fade' or the overheating of the braking system resulting in its efficiency being diminished. As brake fluid is a liquid, it has a boiling point (in most brake fluids it is around 350 Fahrenheit) at which point the liquid expands and turns into a gas. As the brake fluid approaches this boiling point, it starts to expand rapidly, and as the braking system is mostly connected through a series a rubber hoses, these lines start to expand as well. In the end, pressure applied to the braking system by the pedal/master cylinder only causes the lines to expand or 'balloon' even more, rather than transferring that pressure to the braking unit at each wheel.
During panic stops, when the driver depresses the brake pedal as far as it will go and pressure in the hydraulic system is at its highest, the brake pads/shoes can actually lock up against the disk/drum. When lock up occurs, the tires skid over the road as they can no longer roll. This skidding causes a loss of steering input (i.e. control) and increases the braking distance of the car significantly. One system employed on modern cars is called ABS (anti lock brakes) and this lock up is prevented as the pressure applied throughout the system is quickly pulsated when lock up is detected, causing the pads/shoes to release the disk/drums momentarily. This rapid release allows the wheels to continue to roll, thus maintaining control and keeping braking distances as short as possible.
This is in essence the braking system that you will find on any modern car, but some manufacturers of high performance cars have made improvements such as using stainless steel braking lines instead of the common rubber hoses as this material better resists expansion at high temperature.
http://www.essortment.com/hobbies/howbrakeswork_sbof.htm

Auto questions: how four-wheel drive works

Four wheel drive systems have enhanced and helped our abilty to drive in adverse driving conditions. This article will help you to understand how these systems work.
Four-wheel drive (4WD) vehicles have gained mainstream acceptance over the last two decades due to the popularity of the Sport Utility Vehicle in the United States. Car manufacturers also market four-wheel drive vehicles heavily due to their added traction on slippery roads, and during the wintry months dealership sales are normally very strong. So how does the four-wheel drive system work?
The term four-wheel drive is used interchangeably with all-wheel drive and describes the ability of a vehicle to transfer the engine's power to all four wheels. The majority of vehicles on the road do not offer this feature as either the front or rear wheels are driven by the engine's power. However, a four-wheel drive system offers a distinct advantage when traction is limited in slippery conditions - such as on snow, mud, loose gravel or sand - due to four driven wheels offering more traction than two.
There are many different four-wheel drive systems offered on the automotive market today and this can be confusing to the average consumer. Each manufacturer will use a unique term for their specific four-wheel drive system - whether it is Audi's quattro all-wheel drive, Honda's real-time four-wheel drive, Volkswagen's 4Motion or
Mercedes-Benz's 4Matic! However, most of the four-wheel drive systems offered today can be broken down into two main categories:
1) Part-time four-wheel drive
2) All-wheel drive
Part-time four wheel drive: Like its name implies, this form of four-wheel drive powers all four wheels only when the 4WD mechanism is engaged. Typically, these systems power the rear wheels during ideal weather conditions to reduce the wear on the drive train and improve fuel economy, however, when four-wheel drive is engaged, power is transferred to the front wheels as well.
In a part-time four-wheel drive vehicle, the engine's power is transferred to a transfer case inside the transmission that then splits the torque evenly between a front and rear driveshaft (50% to the front, 50% to the rear). The driveshafts are connected to two axle differentials (front and rear), which split power to the wheels at each corner.
During ideal driving conditions, the part-time four-wheel drive system can be disengaged from powering the front axle by unlocking the front hubs (hubs are used on vehicles to attach the driven wheels to the axle). The front hubs are either disengaged manually by the driver, or hydraulically when the driver presses a switch on the dashboard. When the front hubs are disengaged and allowed to spin freely, power from the engine is transferred solely to the rear wheels. To return to four-wheel drive at a later time, the hubs must once again be locked onto the front wheels.
All-wheel drive: This system is gaining popularity and some manufacturers such as Subaru market their vehicles by making their entire model line all-wheel drive. In the typical all-wheel drive system all four wheels are powered at all times. However, unlike a true four-wheel drive vehicle, the power split between the front and rear axles is not set at fixed value (typically 50% front, 50% rear) but can be varied depending on available traction.
All-wheel drive systems typically work by having an active center differential (located in the transmission) that under normal driving conditions splits power evenly between the front and rear axles. However, when driving conditions change and wheel slip is detected at one axle, the center differential responds by transferring more torque to the axle with the most traction. This change in torque split maximizes the traction available at each axle and in extreme conditions it is possible for 100% of power to be transferred to just one axle. However, the normal torque split returns when the vehicle is on a grippy surface again.
One other kind of all-wheel drive system that's becoming relatively common can be best described as part-time all-wheel drive. In this system, either the front or rear axle receives all of the engine's power during normal driving, but when slip is detected, power is transferred to the other axle in just a fraction of a second. Some part-time all-wheel drive systems are so advanced and lightning quick, that the wheels which normally receive 100% of the engine's power only need to slip a sixth of a revolution before power is transferred to the other axle! However, once traction is regained, the vehicle returns to being two-wheel drive once more.
http://www.essortment.com/hobbies/fourwheeldrive_serk.htm

Are honda cars really better than other manufacturers?

Hondas have a reputation for being safe, reliable, and attractive cars. Pros and cons of these automobiles.
Honda is a well-known company that is a leader in the automobile industry. They have a reputation for being the best of the best when it comes to safety, reliability, and value. People who buy Hondas often say that they are confident with their purchase because they are not worried that their new car will be made without care and attention; they believe that they will not have to spend much money on repairs since the cars are known for being so well made. Buyers also have reported that they are happy with their decision to buy a Honda because the re-sale values are so good for Hondas since their durability over time is strong. Not only does Honda have the reputation for making high-quality machinery, but their vehicles are also cited as some of the most attractive mid-priced automobiles on the market. Their vehicles have sleek and stylish lines and curves. From coupe to sedan, from hatch-back to C-RV, Honda truly has been able to make their presence and excellence known amongst consumers. However, when something seems too good to be true, it usually is – so are Honda cars really better than vehicles made by other manufacturer’s, or is it all just hype?
Crash-test ratings are one of the most tangible determinates of a car’s quality, strength, and durability. The Honda Accord, models from 2003 to 2005, ranked good (the highest possible rating) in all areas of the 40 mph frontal crash test. In contrast, the Hyundai Elantra received an overall score of poor on the same crash test, the lowest of four possible scores (good, acceptable, marginal, and poor). The Chevrolet Lumina, however, ranked good in all categories of this crash test – the same score as the Honda Accord. So what does that tell us so far? Hondas may be better than some cars in the crash test department, but they are not trumping the competition in this arena.
Auto mechanics attest that Hondas generally do not require as much unexpected service and maintenance as many other vehicles. The prices for a Honda are usually not much higher than comparable vehicles, but the real savings comes when you analyze how much money you are saving due to the repair ratios. There is no way to determine whether that assertion is statistically true because in order to prove that fact, every auto mechanic, private and commercial, or just people who are qualified to make their own vehicle repairs and just need to buy the parts – they would all have to have kept a diligent records of the stats between makes and models of cars and the total number of repairs that had to be made over the life of each repaired vehicle. However, the overwhelming hypothesis is that Hondas are reliable, and will not deteriorate rapidly after you drive them off the dealership lot. However, that does not prove that Hondas are “better,” and so the debate rages on.
Maybe all that really matters is how the drivers who buy Hondas feel compared to the drivers who buy other cars. Which consumer, on average, was happier with their purchase? Customer satisfaction ratings do not imply that the non-Honda customer is feeling any better, statistically. In conclusion, the question of whether Hondas are better than other cars is impossible to answer because that is a matter of personal opinion, and even if many people can concur that they personally feel Honda is better, that does not make their repeatedly-stated opinions a fact.
http://www.essortment.com/hobbies/hondacarreview_sfak.htm

Auto questions: how horsepower works

Here is the story of horsepower, how it came to be and how it can be calculated in an automobile.
Horsepower is one of those terms which has become so commonplace that our fascination with the origin has all but vanished. In the context of evolution the term horsepower became popularized about five minutes ago. As you may have guessed, the obvious correlation to the horse is indeed the nexus of the equation which horsepower relates to.
We begin our story 268 years ago, far, far away in Glasgow, Scotland. It was a cold and damp morning with a fog that felt like sheets of wet paper. Our character, Mr. James Watt finds himself working with a team of ponies lifting coal in a coal mine. Like so many great thinkers Mr. Watt not only performed a task but he analyzed the layers of even the most mundane of tasks. Watt, being an engineer, began to calculate the amount of coal one horse could move a specified amount of feet every minute. He determined that an average pony can move 22,000 foot pounds of work in one minute. Watt then increases that figure by 50% and 1 horsepower is born, weighing in at 33,000 foot-pounds of work per minute. Simply stated; a horse can raise 330 pounds, 100 feet in the air, in one minute.
Race forward 268 years in five minutes and now lets apply this thinking to my 66' Shelby Cobra in the garage. This car has an engine that produces 425hp and the car weighs in at 2200 lbs. The power to weight ratio for my Cobra is an unbelievable .193. Compare this to a $135,000 Ferrari 355, which has 375hp, and weighs in at 2975lbs., yielding a power to weight ratio of .126, and you tell me who sees who in the rear view.
What you really want to know is, how do I know the Cobra actually has 425hp. The way horsepower is measured today is by measuring torque on a dynamometer, or "dyno", then multiplying by rpm divided by the constant 5252, (torque X rpm/5252). Torque is used as the guide to horsepower because it is easily quantified. Torque is most simply explained as the measure of force in foot pounds applied to an object. For example a one foot wrench that applies 50 foot pounds of force can be made to apply 100 foot pounds of force, with the same amount of energy, by adding a one foot long cheater bar. In the case of a piston driven motor, the pistons and the crank shaft are the equivalent to the wrench in the example above. They are responsible for providing the torque to the drive shaft, which we can now convert to our beloved horsepower.
The dynamometer measures torque by putting a load on, or trying to slow, the engine. The best way to measure this in an automobile is at the drive wheels. This is accomplished by putting the vehicles drive wheels atop a cylinder that has a brake. Imagine a man standing on a floating log and trying to spin it with his feet while you try to stop it, (of course you are laughing sinisterly). The amount of brake pressure on the cylinder is compared against the engines ability to produce rpm's and then you can quantify torque. From torque it is just a stones throw to horsepower: Remember, (torque X rpm/5252). Of course this all adds up to 425hp in my case. Wanna race? (This is the part that I laugh sinisterly.)
P.S. Take a look at any light-bulb. You see the word watt anywhere? That is our guy, James Watt: the father of sacred horsepower, and wattage.
http://www.essortment.com/hobbies/howdoyoumeasu_sdfi.htm

Auto questions: how the bugatti veyron works

Following in its past glories, the soon to be introduced 1001 bhp, $1 million Bugatti Veyron will likely represent the ultimate "supercar".
Mercedes Benz arguably created the first "supercar" when it marketed the 300 SL Gullwing to an awed public in 1954. Since then, most major auto manufacturers have at some point produced their own version of a supercar - exotic, "show car" looks combined with racing car performance and design principles. In the last few years, there have been numerous new entries into this market. The best producers - Porsche, Ferrari, Mercedes Benz (AMG), and Aston Martin - have given the public a group of sensational road cars with performance comparable to all-out racing cars of just a decade ago.
In 2005, the Bugatti EB16-4 Veyron will be introduced to this thriving, but highly competitive market, and will likely establish itself as the ultimate supercar. If maximum speed is an arbiter of success, the Bugatti will have no competition: the company is claming a top speed of 252 mph (though this may be electronically limited to 230 mph or even less, because of concerns over high speed aerodynamic instability). Equally incredible is the claimed acceleration: 0-186 mph (0-300 kph) in less than 14 seconds.
The Bugatti name is not widely known in the U.S. But between 1910 and 1963 this French auto manufacturer produced some of the most highly regarded cars the world has ever known. Certainly the company's glory days were ages ago, before the Great Depression, when the huge, magnificent and extremely rare Royale was produced, and when the light yet powerful Bugatti racing cars were essentially unbeatable in their class. These cars, and others, such as the Type 57 sedan, were both technically brilliant and aesthetically gorgeous.
During the 90's a group of European investors resurrected the Bugatti name and produced a striking, if ill fated, supercar. This car, the first of the modern Bugatti's, the EB110, has no direct ties to its ancestors - save its name and token "horseshoe" air inlet that mimicked the old radiator grill shape. None of these cars were ever certified for sale in the U.S.
Now with the Volkswagen Group as new owners, the Bugatti name is likely to have a much better chance at producing a viable 'world' product. The all-new Veyron is slated for initial production to begin in 2005, the price quoted is an even $1 million per copy. Compliance with U.S. certification requirements is all but guaranteed. So far, only a single prototype has been produced, and it was publicly demonstrated this year at the Pebble Beach Concours d'Elegance in California, where Bugatti was a featured marque. The car made a rather infamous first impression on the audience - and the automotive press - when it took a corner too fast, spun and almost crashed into a barrier; a near disaster that would have surely dealt a horrible blow to the model's development.
In certain respects, the Veyron is very much like most of its top-dollar competition. The handsome styling is born of intensive wind tunnel testing, with carefully planned air inlets and surfaces designed to both minimize drag and high-speed lift. Front and rear overhangs are minimal, and the impressive wheels give an enormous sense of power. Again, the horseshoe grill is used, but much more prominently than in the EB110. Indeed, the oval shape is nicely integrated within the entire design. Photographs released to the public show the Veyron with a handsome two-tone paint scheme, which subtly recalls the pre-WWII multicolored Bugatti sedans. Certainly much of the styling is reflective of "machine age" principles popularized during the 1920's, but which also clearly influences modern cars. Audi's TT coupe and Nissan's Z car are two contemporary examples.
As befits its heritage, probably the most impressive aspect of the new Veyron is its engine. Bugatti's of the past made their names primarily with inline eight-cylinder engines, oftentimes employing a supercharger - a relative rarity even today. Today's Bugatti utilizes an 8-liter W16 engine, which is formed by combining elements of Volkswagen's new and highly compact W8 engine. (To understand the "W" formation, think of two V-engines, sharing a common crankshaft, but with the V's oriented at different angels.)
The new Veyron is reported to produce an astounding 1001 bhp at 6000 rpm. Cars that might be considered competition to the Veyron are currently producing around 500-600 bhp. (For perspective, consider that Charles Lindbergh needed roughly 1/3 that amount to cross the Atlantic). A criticism of the earlier Bugatti EB110 was that its engine did not produce enough low-end torque. This was due to its relatively small displacement of 3.5-liters (which was asked to move almost 4,000 lbs. of car), and to the particular installation of its four turbochargers. These gathered boost in parallel, rather than in sequence (such as on Toyota's Supra). Although this allowed huge top-end performance, it did not provide much power at low rpm. The new engine should have no such complaints: the company quotes 922 lb.-ft. of torque available at 5500 rpm.
The gearbox is equally superlative: a 7-speed paddle activated manual, which allows lightning quick gearshifts - less than 0.2 seconds per shift, which compares very favorably to the usual best of 0.5 seconds available through a conventional manual gearbox. Power is transmitted to a permanent all-wheel-drive system, and finds its way to the road surface via twelve-spoke alloy wheels, measuring 20 in. in diameter that are fitted with Michelin's PAX run-flat tires with P245 fronts and P335s in the rear.
As with any new car, revisions are constantly being made before production. And whether or not Bugatti will be able to actually produce a 252 mph, 1001 bhp, $1 million car is a major question. So far, the announced changes have been limited to the car's dimensions. The wheelbase has grown 2.0 in. from the first show car - it is now 106.0 in. Still, overall length is a tidy 175.8 in, the height is a low 47.5 in., and width is a wide 78.7 in. The name, however is expected to stay the same: EB stands for Ettore Bugatti (the companies founder), 16 for the number of cylinders, 4 for the all-wheel drive, and Veyron for the famous Bugatti driver Pierre Veyron. Like Bugatti's of the past, this will be a very rare car: the Veyron will only contribute to between 50-100 of the approximately 7,950 Bugatti's ever built.
http://www.essortment.com/hobbies/autoquestionsh_sdww.htm