BASIC SUPERCHARGER

A basic engine with the addition of a supercharger.

An ordinary four-stroke engine dedicates one stroke to the process of air intake. There are three steps in this process:

11.     The piston moves down.

22.     This creates a vacuum.

33.     Air at atmospheric pressure is sucked into the combustion chamber.

Once air is drawn into the engine, it must be combined with fuel to form the charge -- a packet of potential energy that can be turned into useful kinetic energy through a chemical reaction known as combustion. The spark plug initiates this chemical reaction by igniting the charge. As the fuel undergoes oxidation, a great deal of energy is released. The force of this explosion, concentrated above the cylinder head, drives the piston down and creates a reciprocating motion that is eventually transferred to the wheels.

How Superchargers Work

Since the invention of the internal combustion engine, automotive engineers, speed junkies and race car designers have been searching for ways to boost its power. ­One way to add power is to build a bigger engine. But bigger engines, which weigh more and cost more to build and maintain, are not always better.

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USING TWO TURBOCHARGERS

Using Two Turbochargers & More Turbo Parts

Some engines use two turbochargers of different sizes. The smaller one spins up to speed very quickly, reducing lag, while the bigger one takes over at higher engine speeds to provide more boost.

When air is compressed, it heats up; and when air heats up, it expands. So some of the pressure increase from a turbocharger is the result of heating the air before it goes into the engine. In order to increase the power of the engine, the goal is to get more air molecules into the cylinder, not necessarily more air pressure.

TURBOCHARGER PARTS

Turbocharger Parts

One of the main problems with turbochargers is that they do not provide an immediate power boost when you step on the gas. It takes a second for the turbine to get up to speed before boost is produced. This results in a feeling of lag when you step on the gas, and then the car lunges ahead when the turbo gets moving.

Turbochargers provide boost to engines at high speeds

TURBOCHARGER DESIGN

Turbocharger Design

The turbocharger is bolted to the exhaust manifold of the engine. The exhaust from the cylinders spins the turbine, which works like a gas turbine engine. The turbine is connected by a shaft to the compressor, which is located between the air filter and the intake manifold. The compressor pressurizes the air going into the pistons.

How a turbocharger is plumbed in a car

TURBOCHARGERS AND ENGINES

Turbochargers and Engines

One of the surest ways to get more power out of an engine is to increase the amount of air and fuel that it can burn. One way to do this is to add cylinders or make the current cylinders bigger. Sometimes these changes may not be feasible -- a turbo can be a simpler, more compact way to add power, especially for an aftermarket accessory.

Turbochargers allow an engine to burn more fuel and air by packing more into the existing cylinders. The typical boost provided by a turbocharger is 6 to 8 pounds per square inch (psi). Since normal atmospheric pressure is 14.7 psi at sea level, you can see that you are getting about 50 percent more air into the engine. Therefore, you would expect to get 50 percent more power. It's not perfectly efficient, so you might get a 30- to 40-percent improvement instead.

One cause of the inefficiency comes from the fact that the power to spin the turbine is not free. Having a turbine in the exhaust flow increases the restriction in the exhaust. This means that on the exhaust stroke, the engine has to push against a higher back-pressure. This subtracts a little bit of power from the cylinders that are firing at the same time.­

How Turbochargers Work

When people talk about cars or high-performance sports cars, the topic of turbochargers usually comes up. Turbochargers also appear on large diesel engines. A turbo can significantly boost an engine's horsepower without significantly increasing its weight, which is the huge benefit that makes turbos so popular!

In this article, we'll learn how a turbocharger increases the power output of an engine while surviving extreme operating conditions. We'll also learn how waste gates, ceramic turbine blades and ball bearing help turbochargers do their job even better. Turbochargers are a type of forced induction system. They compress the air flowing into the engine. The advantage of compressing the air is that it lets the engine squeeze more air into a cylinder, and more air means that more fuel can be added. Therefore, you get more power from each explosion in each cylinder. A turbocharged engine produces more power overall than the same engine without the charging. This can significantly improve the power-to-weight ratio for the engine

In order to achieve this boost, the turbocharger uses the exhaust flow from the engine to spin a turbine, which in turn spins an air pump. The turbine in the turbocharger spins at speeds of up to 150,000 rotations per minute (rpm) -- that's about 30 times faster than most car engines can go. And since it is hooked up to the exhaust, the temperatures in the turbine are also very high.

THE FUTURE OF POWER STEERING

The Future of Power Steering

Since the power-steering pump on most cars today runs constantly, pumping fluid all the time, it wastes horsepower. This wasted power translates into wasted fuel.

You can expect to see several innovations that will improve fuel economy. One of the coolest ideas on the drawing board is the "steer-by-wire" or "drive-by-wire" system. These systems would completely eliminate the mechanical connection between the steering wheel and the steering, replacing it with a purely electronic control system. Essentially, the steering wheel would work like the one you can buy for your home computer to play games. It would contain sensors that tell the car what the driver is doing with the wheel, and have some motors in it to provide the driver with feedback on what the car is doing. The output of these sensors would be used to control a motorized steering system. This would free up space in the engine compartment by eliminating the steering shaft. It would also reduce vibration inside the car.

General Motors has introduced a concept car, the Hy-wire that features this type of driving system. One of the most exciting things about the drive-by-wire system in the GM Hy-wire is that you can fine-tune vehicle handling without changing anything in the car's mechanical components -- all it takes to adjust the steering is some new computer software. In future drive-by-wire vehicles, you will most likely be able to configure the controls exactly to your liking by pressing a few buttons, just like you might adjust the seat position in a car today. It would also be possible in this sort of system to store distinct control preferences for each driver in the family.

In the past fifty years, car steering systems haven't changed much. But in the next decade, we'll see advances in car steering that will result in more efficient cars and a more comfortable ride.

POWER STEERING.

Power Steering

There are a couple of key components in power steering in addition to the rack-and-pinion or recirculating-ball mechanism.

RECIRCULATING BALL STEERING

Recirculating-ball Steering

Recirculating-ball steering is used on many trucks and SUVs today. The linkage that turns the wheels is slightly different than on a rack-and-pinion system.

STEERING RACK AND PINION

Rack-and-pinion Steering

Rack-and-pinion steering is quickly becoming the most common type of steering on cars, small trucks and SUVs. It is actually a pretty simple mechanism. A rack-and-pinion gear set is enclosed in a metal tube, with each end of the rack protruding from the tube. A rod, called a tie rod, connects to each end of the rack.

The pinion gear is attached to the steering shaft. When you turn the steering wheel, the gear spins, moving the rack. The tie rod at each end of the rack connects to the steering arm on the spindle (see diagram above).

The rack-and-pinion gear set does two things:

·         It converts the rotational motion of the steering wheel into the linear motion needed to turn the wheels.

·         It provides a gear reduction, making it easier to turn the wheels.

On most cars, it takes three to four complete revolutions of the steering wheel to make the wheels turn from lock to lock (from far left to far right).

How Car Steering Works

You know that when you turn the steering wheel in your car, the wheels turn. Cause and effect, right? But a lot of interesting stuff goes on between the steering wheel and the tires to make this happen.

In this article, we'll see how the two most common types of c­ar steering systems work: rack-and-pinion and recirculating-ball steering. Then we'll examine power steering and find out about some interesting future developments in steering systems, driven mostly by the need to increase the fuel efficiency of cars. But first, let's see what you have to do turn a car. It's not quite as simple as you might think!

Turning the Car

You might be surprised to learn that when you turn your car, your front wheels are not pointing in the same direction.

For a car to turn smoothly, each wheel must follow a different circle. Since the inside wheel is following a circle with a smaller radius, it is actually making a tighter turn than the outside wheel. If you draw a line perpendicular to each wheel, the lines will intersect at the center point of the turn. The geometry of the steering linkage makes the inside wheel turn more than the outside wheel.

FOUR WHEEL DRIVE DIFFERENTIAL

Four-wheel Drive Differential

The type of part-time system typically found on four-wheel-drive pickups and older SUVs works like this: The vehicle is usually rear-wheel drive. The transmission hooks up directly to a transfer case. From there, one drive shaft turns the front axle, and another turns the rear axle.

When four-wheel drive is engaged, the transfer case locks the front drive shaft to the rear drive shaft, so each axle receives half of the torque coming from the engine. At the same time, the front hubs lock.

COMPONENTS OF A FOUR WHEEL DRIVE SYSTEM.

Components of a Four-wheel-drive System

The main parts of any four-wheel-drive system are the two differentials (front and rear) and the transfer case. In addition, part-time systems have locking hubs, and both types of systems may have advanced electronics that help them make even better use of the available traction.

TORQUE, TRACTION AND WHEEL SLIP

Torque, Traction and Wheel Slip

Torque is the twisting force that the engine produces. The torque from the engine is what moves your car. The various gears in the transmission and differential multiply the torque and split it up between the wheels. More torque can be sent to the wheels in first gear than in fifth gear because first gear has a larger gear-ratio by which to multiply the torque.

The bar graph below indicates the amount of torque that the engine is producing. The mark on the graph indicates the amount of torque that will cause wheel slip. The car that makes a good start never exceeds this torque, so the tires don't slip; the car that makes a bad start exceeds this torque, so the tires slip. As soon as they start to slip, the torque drops down to almost zero.

The interesting thing about torque is that in low-traction situations, the maximum amount of torque that can be created is determined by the amount of traction, not by the engine. Even if you have a NASCAR engine in your car, if the tires won't stick to the ground there is simply no way to harness that power.

For the sake of this article, we'll define traction as the maximum amount of force the tire can apply against the ground (or that the ground can apply against the tire -- they're the same thing). These are the factors that affect traction:

The weight on the tire -- The more weight on a tire, the more traction it has. Weight can shift as a car drives. For instance, when a car makes a turn, weight shifts to the outside wheels. When it accelerates, weight shifts to the rear wheels. 

The coefficient of friction -- This factor relates the amount of friction force between two surfaces to the force holding the two surfaces together. In our case, it relates the amount of traction between the tires and the road to the weight resting on each tire. The coefficient of friction is mostly a function of the kind of tires on the vehicle and the type of surface the vehicle is driving on. For instance, a NASCAR tire has a very high coefficient of friction when it is driving on a dry, concrete track. That is one of the reasons why NASCAR race cars can corner at such high speeds. The coefficient of friction for that same tire in mud would be almost zero. By contrast, huge, knobby, off-road tires wouldn't have as high a coefficient of friction on a dry track, but in the mud, their coefficient of friction is extremely high.

HOW FOUR WHEEL DRIVE WORKS.

How Four-Wheel Drive Works

There are almost as many different types of four-wheel-drive systems as there are four-wheel-drive vehicles. It seems that every manufacturer has several different schemes for providing power to all of the wheels. The language used by the different car makers can sometimes be a little confusing, so before we get started explaining how they work, let's clear up some terminology:

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