Subwoofer Enclosure - Tricks Of The Trade

This month we'll finish up the subwoofer enclosure in our '07 Project Toyota Avalon. This enclosure demonstrates how a large subwoofer can be integrated cleanly into a trunk while maintaining trunk space. It's also a perfect spot to put a subwoofer, since it loads correctly with the vehicle's interior and avoids cancellation. This is by far one of my favorite enclosure building techniques and I've used it in many vehicles with success. If you're looking to take back some of your trunk or hatch space, do yourself a favor and spend a weekend or two integrating your subwoofer into your vehicle-you won't regret it. Send questions to techpanel@sourceinterlink.com with Tricks of the Trade in the subject line, and check out stevebrownuniversity.com.
Since we finished the back or base of the enclosure last month, we bolted it in the car to check the fit. Next, attach the ring that holds the speaker to the enclosure base. CA glue, or super glue, works great to temporarily tack the ring in place while the fit is checked. Be sure to allow enough depth for the subwoofer to mount properly without hitting the back of the enclosure. Using Duraglas, bond each of the braces to the enclosure.
After trimming off the excess carpet, your enclosure should look like this. Notice the green masking tape applied to all exposed edges, necessary to keep fiberglass resin out of these areas. This little trick will save tons of time later, since you won't have to grind the excess resin out from where you don't want it. Make a ring from two layers of 31/44" MDF to mount the subwoofer. Notice that the bottom ring is smaller than the top one in order to mount the subwoofer and also make it flush with the surface of the box when complete. Route a notch, or rabbet, into the outside edge to make it easy to staple on our surfacing material later.
If you plan on bolting an amplifier to the enclosure, add a 31/44" MDF plate ahead of the subwoofer ring as a place to mount it. Note the rabbeted notch added to this panel. With the frame structure complete, it's time to add our shaping material to the front of the enclosure. This makes the box very strong, seals it up and creates the final shape of the front side. Non-backed stretchy carpet works great for this, since it's thick and durable when soaked with resin. Pull the carpet tight over the box surface and attach the carpet to the edges of the fiberglass base using CA glue.

Speaker Pods - Door Pod Express

Creating a quality audio system requires more than just good speakers. In order to create a well-balanced soundstage, the speakers need proper placement-not always an easy task when dealing with the tight spaces of modern cars. Many times we have to relegate ourselves to modifying the factory placements for better imaging. One way to do this is building new door panels, which is a pretty complicated endeavor. There are, however, more simple methods of achieving this goal.
Depending on the vehicle, there are options using factory panels or grilles. For our Nissan 350Z, we used the factory door speaker grilles as a base for our pods. By modifying the factory panels, we can change the directional imaging of the speakers, creating a well-balanced soundstage.
ImagingBefore any actual mods can begin, the speakers should be imaged. This is a lengthy process that involves listening tests and aiming the speakers, but with a couple of shortcuts, the results can be pretty amazing. One of the best tricks for quick imaging is to aim the driver's-side midrange at the passenger's left ear and the passenger's-side speaker, at the driver's right ear. This will create a cross point in the center of the vehicle, equalizing the path lengths as much as possible without relocating the speakers. If you're using components, try aiming the tweeter at the rearview mirror or a centered point 3-4' in front of the passenger's head. This creates a separation that allows both waves to hit the listener's ears at nearly the same time. These tricks don't work perfectly all the time and probably won't win any SQ competitions but, for a daily driver, they offer better imaging without hours of testing.
The build process is pretty simple and requires very little tools. If you have access to an air compressor, a DA sander and a die-grinder, they'll be your best friend, and allow you to save time when shaping and sanding parts. If not, you can always do it the old-fashioned way and sand by hand. If you must hand sand, don't wait until the body filler is fully cured. Instead, let it go green-the stage in which the filler is just beyond rubber. If you start your rough shaping now, the filler will roll-off quickly and easily, letting you get the shape you want faster and with less fatigue. The entire process is detailed here with Jason Carson of Red Dirt Rodz doing the dirty work. Just remember, a little patience goes a long way in this business-rushing the job will only make it take longer.
We started the project with a pair of 31/44" MDF rings that we cut to match the outside diameter of the Kicker speaker grilles. Once we decided the best angle for the speakers, we used a die-grinder to sand and angle the topside of the ring. This can be done with a belt sander as well.
We placed the rings on the door panels and rotated them until we had the placement we wanted. The rings need to be smaller than the door grille. Ours are roughly 0.5" smaller overall.
We scuffed the door grilles (for better adhesion) and glued the rings to the grilles.

Fiberglass Quarter-Panel Fabrication - JS Designs/Sony Civic Si 3 4

Fiberglass Quarter-Panel FabricationThis month we'll look at the construction of the fiberglass trim panels for the rear quarter-panel area (sides of the back seat). In my early planning stages, one of my goals for the JS Designs Honda Civic Si was to have an extremely loud and fun system. Basically, while driving the car I wanted it to sound like a concert or a dance club. To accomplish this, I integrated six sets of Sony XS-D170SI speakers into the car as a whole, with two component sets for each third of the vehicle.
For example, my design called for two component sets in the front doors, two in the back seat panels and two in the rear hatch. This division of the component sets created a balance of sound in the car from front to back; I had already created the ported subwoofer enclosure for three 12" subs. Five 8" speakers equaled the active radiating area (or SD ROM) of the three 12" drivers, the Sony drivers are 6.75" so 12 of these drivers are more than capable of keeping up with the high excursion of the Sony subwoofers.
Two of the six sets were placed into newly fabricated rear trim panels for the back seat. These panels sit adjacent to the large, fiberglass amprack that holds the six Sony amplifiers and 12 Sony LCD monitors. I wanted the panels to fit in the same way that the factory panels fit plus I wanted them to serve as a trim panel over the enclosure for the 6.5" component set. The panels were designed in a way so that the overall shape flowed with the factory lines of the car and, in the end, enabled all of the back seat panels to flow together as one shape.
Next month, we'll take a break from the Civic Si construction and examine how to do some clean, structured wiring. In the meantime, if you would like any additional pictures or information, please feel free to contact me at info@jasonsyner.com.
Using the side of the amprack as a template, a piece of MDF was cut and flush-routed to match its shape. This piece will later become the outer framework for the side panel, which will also be used to transition the side panel into those I built for the backseat area. When I used a router/lift combo (available from www.mobilesolutions-usa.com) speaker openings were cut into the panel and flush-routed. To trim in the speaker grilles, 11/42" MDF rings were cut. Eighth-inch stainless steel brackets bolt the MDF to the supporting metal in the quarter-panels of the vehicle. This picture shows the MDF panel bolted into place inside the vehicle. This picture shows the speakers test-fitted into the enclosure.

Custom Upholstery

In this issue we are going to move on to the next phase of the interior on our project 635csi, or "Bavarian Baller." Here we cover custom upholstery for the front and rear seats. While we want to maintain that classic 635 look, we also want to give it the appearance of custom. To do this, we're going to dress up the front and rear seats with sandstone gray suede inserts, satin black genuine leather and, to give it a sporty appearance, sandstone gray piping trim.
Next Rick will remove the headrest and the left and right recliner mechanism (Note the torque cable that connects at the front lower section of each recliner mechanism). To disconnect, carefully remove the faceplate at the lower section of each recliner mechanism, detach the cable and reinstall the faceplate so that the gears inside don't fall out. Later we'll follow this same process during reassembly.
Now that the seat cover is removed, put locator markings (use chalk or a pen) on the old seat cover where you feel it might be important. These marks will be transferred onto the new material when you begin cutting out the patterns. These locator marks are very helpful when sewing together the new seat cover because they keep all parts aligned and in their proper place.
Unstitch the old seat cover into its individual parts. To do this, most trimmers use a one-sided razor blade-be very careful! Using a razor blade is fast and easy, but caution must be taken when in use and after use. Never throw razor blades in a trash can-use a small canister with a lid, ask someone or call the razor manufacturer for the proper disposal procedure. I know this sounds silly, but I've seen a guy go and search the trash can for a misplaced part only to come out with a bloody thumb and pass out on the floor.
Note: Bucket seats usually have a left and right seat. If this is the case with your project, cut out all the patterns for the front passenger seat bottom first and write "PASS" on the edge of all the new pieces to identify them as the passenger seat pattern. After cutting out the patterns, flip each one over face down and use them to trace out the patterns for the driver's side and mark those "DR" to identify them as the driver's side. This way we won't mix our passenger patterns with the driver's side patterns because if we did, we'd end up with some Quasimodo-looking seats.
This method works well for beginners because the old seat covers are actually teaching you how to make patterns and how a seat cover is constructed. Later you'll develop your own method of pattern making and how to construct a seat cover. For now though we will use this same process of unstitching, marking old seat covers and flipping patterns for the front and rear seats.
Before upholsterer Rick Mena gets started, here are some notes:Have a marker, masking tape, plastic ziplock bags and, if possible, a digital camera. Use the marker and tape to label electrical plugs, seat tracks mechanism, recliner mechanism, etc. Use the plastic bags for your different screws and small parts. Label each bag so you can quickly identify them later. With the digital camera you can take all the pictures you want and use them later for quick reference.

Installing Capacitors - How To

This month I took a break from my Civic Si build project to look at a subject that I'm frequently asked about-capacitors and how to wire them correctly. Here is a hands-on approach to install capacitors and trunk-mounted batteries.
To start, I'll explain what a car audio capacitor really is. It's a storage device for electrons (electricity) and is very similar to a battery. But the main difference between the two is that a battery uses chemical reactions to produce the electrons while a capacitor simply stores energy. A capacitor consists of two conducting plates separated by an insulating piece or dielectric. Car audio capacitors store energy for dynamic peaks, which can greatly improve your stereo system. Extra batteries produce and store energy for extended play on your stereo system. Capacitors discharge very rapidly, while batteries tend to discharge very slowly.
Capacitance, or the amount of energy stored, is measured in farads. Most car audio capacitors are one-half, or 1 farad. Capacitors should be pre-charged before installation. This enables them to reach their maximum storage limit without damaging the electrolytic. It also allows the unit to be installed without arc-welding your connection to the teminal. Use care when charging a capacitor and always do it with a resistor. I typically use a 100-watt, 8-ohm resistor, available at most electronic surplus stores. Most caps come with a 1K resistor, which will work but will take a while and the leads will get extremely hot. If you must use this resistor, hold it in place with pliers. First, ground your capacitor. Then, before connecting 12-volt power to your cap, take out the fuse under your hood and put the resistor in its place. Basically, just touch the leads where the fuse would normally go. Next, connect power to the capacitor. It's also a good idea to have your voltmeter monitoring the cap's terminals so that you can watch the charging process. Once the cap gets up to 12 volts you can take out the resistor and reinstall your fuse.
Capacitors should be placed within inches of your amp in order to maximize the performance of your system. It's also important to remember that, while a fuse should be used to protect your system, it must be placed on the charging line feeding the capacitor, NOT after. A fuse inserted between the capacitor and amplifier becomes a resistor, essentially rendering the capacitor useless.Next month we will continue on with the Civic build and take a look at the creation of some custom parts of the car. Until then, e-mail me your thoughts and questions: info@jasonsyner.com.

Body Kit Part 1 - How -To

This month we are starting a two-part article on the installation steps and custom bodywork required to install an aftermarket body kit on my project Civic, which includes several handmade additions. The methods presented in this article can be used as a guideline for most body kit installations. Keep in mind that all body kit components must be securely bolted to your car so that they cannot be dislodged during high-speed travel or in the event of a collision.
Most custom cars have some sort of extra body components and almost all tuner cars seen at car shows have some sort of aftermarket body kit. When I'm at car shows, the first thing that people usually ask me about is the body kit on my '05 Civic Si. When I purchased the body kit, I already had plans to add some custom pieces of my own to accent the factory bodylines of the Civic and this particular kit enabled me to do just that.
You can use many different techniques for installing a body kit. A cordless drill, a tap-and-die set and stainless steel SAE bolts were the tools that I used to attach the body kit to my car. Some shops use a product called Panel Bond by 3M, which is a permanent attachment to the car, and it greatly reduces your working time. My approach takes a little more execution and time, but gives me the flexibility to remove any single piece of the 11-piece body kit at any time. In the event that it gets scratched, cracked or damaged, I can simply detach the damaged piece and repair it without having to touch any of the other pieces on the car.
Body kits are usually made out of fiberglass, and the more expensive kits are usually made out of polyurethane. The kit I chose had a mixture of polyurethane and fiberglass parts. The poly parts are the lower body components on the car and have a flexible structure. In the event that they rub on the pavement or a curb, they won't crack like rigid fiberglass parts might.
I have installed numerous body kits over the years from various manufacturers and all of the kits needed a lot of custom bodywork before installation. This kit was no exception, despite its high price tag. I was determined to make it work on the car, and hopefully this article will help others with their body kit installations.
Next month, we'll continue this two-part article and look at the custom paintwork on the body kit and the custom hood. Until then e-mail your questions or comments to info@jasonsyner.com.

Continental Drift - Realm 1963 Lincoln Continental

Car audio upstart realm knows class when it sees it. The two-yearold california company needed a vehicle to effectively showcase its line of loudspeakers, amplifiers and low-frequency transducers. While most outfits would go straight to the newest thing on the block, realm instead looked backwards and found itself a '63 Lincoln continental, complete with front and back bench seats and suicide doors. "Sweet" doesn't even begin to describe it.

Before the continental could be suitable for an audio installation, it had to have a little work done. in-house experts Trevor Kaplan and Nathan Perkins, who would also tackle the audio portion of the installation, went to work on the Kennedy-era Lincoln, straightening and smoothing bodylines, adding a factory-restored Lincoln Land suspension and custom stainless steel exhaust system. The 430cid engine was rebuilt by Extreme automotive, and coats of Porsche charcoal gray and metallic silver were added by L&g autobody in San dimas, ca. Lastly, 288ft of accumat Hyperflex amT060HF sound damping material was tucked in around the entire vehicle. The car also received a box of accumat amT250 sound barrier on the floor of the passenger cabin. as Kaplan says, "a big car requires a lot of mat."

Head UnitSitting high and front and enter in the Lincoln's dash is a Pioneer dEHP790bT head unit. To make the modern component fit in this classic dash, a trim ring was customfabricated using the original radio's faceplate as a template. Thus, the classic lines were maintained without remaining slavish to tradition.

Front And Rear SpeakersThe get the proper sound upfront, the realm team decided to think outside of the box and create a 3-way component set from two different pre-existing sets. First, realm LS5c 5.25" component sets were installed in custom-molded kick panels fabricated from floating wood rings and wrapped in fiberglass. To round out the sound, a 6" woofer from the company's LS6c 6.5" component set was installed in each front door and bandpassed using a passive crossover network. The midbass woofers were molded into the door pulls by forming wood and stretching glass over the support structure to achieve the desired shape.
For the rear suicide doors, realm LS6c 6.5" components were molded into the rear door pulls to match the front. "The rear speakers are on a separate amp, which can be independently turned off for SQ front staging," Kaplan explains.

AmplificationA total of six amps make up the amplification array in the continental's trunk, placed just in front of the sub box. Three realm d500.1 class d amps power the three LFT12-d4 woofers, one per at a 2-ohm load. additionally, three realm a300.2 2-channel amps power the component sets: one to the kick panel 5.25" components, one to the 6" midbass door speakers and one to the 6" rear door components.
Rounding out the install are an EFx Edc1700 battery under the hood in the stock location and an EFx Edc1200 battery in the trunk, connected to the distribution blocks. EFx cable and speaker wire were used throughout.

SubwoofersYou'd think a vehicle like a '63 Lincoln continental would have plenty of trunk space with which to achieve loud and tight bass. However, you would be wrong. "as big as the trunk is in that car," Kaplan reveals, "the shape [of the trunk interior] and rear axle hump ate up much of the space, barely leaving us room for our box and amprack." So what did they manage to squeeze into the back of the continental? Try three realm LFT12-d4 subwoofers, two firing into the vehicle and the middle into the box itself. The subwoofer enclosure was made of mdF with an acrylic face and top. Stainless steel sheets cover the mdF. The sub enclosure ended up yielding 2.7ft altogether, or 0.9ft per woofer.

What is the difference between a turbocharger and a supercharger on a cars engine?

Let's start with the similarities. Both turbochargers and superchargers are called forced induction systems. They compress the air flowing into the engine (see How Car Engines Work for a description of airflow in a normal engine). The advantage of compressing the air is that it lets the engine stuff more air into a cylinder. More air means that more fuel can be stuffed in, too, so you get more power from each explosion in each cylinder. A turbo/supercharged engine produces more power overall than the same engine without the charging.

Turbocharger Image Gallery

The typical boost provided by either a turbocharger or a supercharger 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, though, so you might get a 30-percent to 40-percent improvement instead.

The key difference between a turbocharger and a supercharger is its power supply. Something has to supply the power to run the air compressor. In a supercharger, there is a belt that connects directly to the engine. It gets its power the same way that the water pump or alternator does. A turbocharger, on the other hand, gets its power from the exhaust stream. The exhaust runs through a turbine, which in turn spins the compressor (see How Gas Turbine Engines Work for details).

There are tradeoffs in both systems. In theory, a turbocharger is more efficient because it is using the "wasted" energy in the exhaust stream for its power source. On the other hand, a turbocharger causes some amount of back pressure in the exhaust system and tends to provide less boost until the engine is running at higher RPMs. Superchargers are easier to install but tend to be more expensive.

What if I put a one horsepower engine into my car?

A typical car in America has something around a 120-horsepower engine. A big SUV might have a 200-horsepower engine, and a tiny car might have only 70 horsepower. A moped, on the other hand has only a 1- or 2- horsepower engine, and it gets great gas mileage -- 70 or 80 miles per gallon. So why not put a little engine in a car to give its mileage a boost?

One reason is that a car needs a fair amount of power to make its way down the road. At 60 mph, a typical car needs 10 to 20 horsepower simply to maintain its speed. That energy level is needed to overcome wind resistance and the rolling resistance in the tires. If you have the headlights on, the alternator is using power to generate electricity for the lights. If the air conditioner is on, that takes power too. A 1-horsepower engine couldn't maintain more than 20 or 30 mph in a normal car, and you could never turn on the headlights or the air conditioning.

The other problem is acceleration. The bigger the engine, the faster you can accelerate from zero to 60mph. With a 1-horsepower engine, you might need a couple of minutes to accelerate up to 60mph, even if there was no such thing as wind resistance.

If you wanted to make a car that could run on a 1 horsepower engine, you would need to make it a tiny, lightweight, extremely aerodynamic one-seater. It would look more like a cold capsule than a car. By making it tiny and lightweight, you would be able to accelerate quickly even with limited power. Because it would be minuscule and aerodynamic, you would reduce its wind resistance so much that a 1-horsepower engine could keep it moving at 60 or 70 mph without any trouble. That would give you a high-mileage car.

What if I pumped pure oxygen into my car engine instead of using the air in the atmosphere?

The internal combustion engine in most cars burns gasoline. To do the burning, an engine needs oxygen, and the oxygen comes from the air all around us. But what if cars carried their own and pumped pure oxygen into the engine instead?

The air around us is about 21 percent oxygen. Almost all the rest is nitrogen, which is inert when it runs through the engine. The oxygen controls how much gasoline an engine can burn. The ratio of gas to oxygen is about 1:14 -- for each gram of gasoline that burns, the engine needs about 14 grams of oxygen. The engine can burn no more gas than the amount of oxygen allows. Any extra fuel would come out of the exhaust pipe unburned.

So if the car used pure oxygen, it would be inhaling 100 percent oxygen instead of 21 percent oxygen, or about five times more oxygen. This would mean that it could burn about five times more fuel. And that would mean about five times more horsepower. So a 100-horsepower engine would become a 500-horsepower engine!

It would take more oxygen tanks than you could fit in your car to have enough oxygen to power your engine

What does it mean when a car has dual overhead cams?

Generally, engines with dual overhead camshafts (DOHC) are higher performance engines, they produce more power, and can run at higher speeds.

The camshafts have the job of opening the valves that let air into and exhaust out of the engine. The camshaft uses rotating lobes, called cams, that push against the valves to open them. 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.

The main benefit of dual overhead cams is that they allow an engine to have four valves per cylinder. Each camshaft operates two of the valves, one camshaft handles the intake valves, and one handles the exhaust valves.

A cutaway dual overhead cam engine

Having four valves per cylinder gives an engine several advantages.

• By having four valves in a cylinder instead of two, a larger portion of the area can be used to let air in and exhaust out. The engine can make more power if more air enters the cylinder, and it wastes less power if it is easier to pump the exhaust out of the cylinder.

  At higher engine speeds, the engine pumps a lot of air though the cylinders. Having four valves per cylinder allows the engine to pump enough air to run and make useful power at these higher speeds.

• Another interesting thing that some car makers do is have a separate intake runner for each of the two intake cylinders. One of the intake runners is wide and short for maximum airflow, the other is a tuned intake runner.

  When the intake valve is open on the engine, air is being sucked into the engine, so the air in the intake runner is moving rapidly toward the cylinder. When the intake valve closes suddenly, this air slams to a stop and stacks up on itself, forming an area of high pressure. This high-pressure wave makes its way up the intake runner away from the cylinder. When it reaches the end of the intake runner, where the runner connects to the intake manifold, the pressure wave bounces back down the intake runner.

  If the intake runner is just the right length, that pressure wave will arrive back at the intake valve just as it opens for the next cycle. This extra pressure helps cram more air-fuel mix into the cylinder -- effectively acting like a turbocharger.

How Turbochargers Work

When people talk about race 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 wastegates, ceramic turbine blades and ball bearings help turbochargers do their job even better. Turbochargers are a type of forced induction system. They compress the air flowing into the engine (see How Car Engines Work for a description of airflow in a normal 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 (see How Horsepower Works for details).

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 Basics
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.

Turbocharger Image Gallery

Where the turbocharger is located in the car. See more turbocharger images.

­ 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 Superchargers Work

Since the invention of the internal combustion engine, automotive engineers, speed junkies and racecar 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.

Superchargers Image Gallery

Photo courtesy Superchargers Online Ford Ranger with a supercharger under the hood. See more supercharger pictures.

Another way to add power is to make a normal-sized engine more efficient. You can accomplish this by forcing more air into the combustion chamber. More air means more fuel can be added, and more fuel means a bigger explosion and greater horsepower. Adding a supercharger is a great way to achieve forced air induction. In this article, we'll explain what superchargers are, how they work and how they compare to turbochargers.
Superchargers and Turbochargers
A supercharger is any device that pressurizes the air intake to above atmospheric pressure. Both superchargers and turbochargers do this. In fact, the term "turbocharger" is a shortened version of "turbo-supercharger," its official name.

Photo courtesy HowStuffWorks Shopper A twin-screw supercharger

The difference between the two devices is their source of energy. Turbochargers are powered by the mass-flow of exhaust gases driving a turbine. Superchargers are powered mechanically by belt- or chain-drive from the engine's crankshaft.

In the next section, we'll look at how a supercharger does its job.

How Camshafts Work

If you have read the article How Car Engines Work, you know about the valves that let the air/fuel mixture into the engine and the exhaust out of the engine. 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.

Camshaft Image Gallery

The camshaft (click on image to see animation).
See more pictures of camshafts.

In this article, you will learn how the camshaft affects engine performance. We've got some great animations that show you how different engine layouts, like single overhead cam (SOHC) and double overhead cam (DOHC), really work. And then we'll go over a few of the neat ways that some cars adjust the camshaft so that it can handle different engine speeds more efficiently.

Let's start with the basics.

Camshaft Basics
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.

This setup would work really well for the engine as long as it ran at this very slow speed. But what happens if you increase the RPM? Let's find out.

When you increase the RPM, the 10 to 20 RPM configuration for the camshaft does not work well. If the engine is running at 4,000 RPM, the valves are opening and closing 2,000 times every minute, or 33 times every second. At these speeds, the piston is moving very quickly, so the air/fuel mixture rushing into the cylinder is moving very quickly as well.

When the intake valve opens and the piston starts its intake stroke, the air/fuel mixture in the intake runner starts to accelerate into the cylinder. By the time the piston reaches the bottom of its intake stroke, the air/fuel is moving at a pretty high speed. If we were to slam the intake valve shut, all of that air/fuel would come to a stop and not enter the cylinder. By leaving the intake valve open a little longer, the momentum of the fast-moving air/fuel continues to force air/fuel into the cylinder as the piston starts its compression stroke. So the faster the engine goes, the faster the air/fuel moves, and the longer we want the intake valve to stay open. We also want the valve to open wider at higher speeds -- this parameter, called valve lift, is governed by the cam lobe profile.

The animation below shows how a regular cam and a performance cam have different valve timing. Notice that the exhaust (red circle) and intake (blue circle) cycles overlap a lot more on the performance cam. Because of this, cars with this type of cam tend to run very roughly at idle.

Two different cam profiles: Click the button under the play button to toggle between cams. The circles show how long the valves stay open, blue for intake, red for exhaust. The valve overlap (when both the intake and exhaust valves are open at the same time) is highlighted at the beginning of each animation.

Any given camshaft will be perfect only at one engine speed. At every other engine speed, the engine won't perform to its full potential. A fixed camshaft is, therefore, always a compromise. This is why carmakers have developed schemes to vary the cam profile as the engine speed changes.

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

In the next section, we'll look at each of these configurations.

How Horsepower Works

Chances are you've heard about horsepower. Just about every car ad on TV mentions it, people talking about their cars bandy the word about and even most lawn mowers have a big sticker on them to tell you the horsepower rating.

But what is horsepower, and what does the horsepower rating mean in terms of performance? In this article, you'll learn exactly what horsepower is and how you can apply it to your everyday life.

The term horsepower was invented by the engineer James Watt. Watt lived from 1736 to 1819 and is most famous for his work on improving the performance of steam engines. We are also reminded of him every day when we talk about 60-watt light bulbs.

The story goes that Watt was working with ponies lifting coal at a coal mine, and he wanted a way to talk about the power available from one of these animals. He found that, on average, a mine pony could do 22,000 foot-pounds of work in a minute. He then increased that number by 50 percent and pegged the measurement of horsepower at 33,000 foot-pounds of work in one minute. It is that arbitrary unit of measure that has made its way down through the centuries and now appears on your car, your lawn mower, your chain saw and even in some cases your vacuum cleaner.

What horsepower means is this: In Watt's judgement, one horse can do 33,000 foot-pounds of work every minute. So, imagine a horse raising coal out of a coal mine as shown above. A horse exerting 1 horsepower can raise 330 pounds of coal 100 feet in a minute, or 33 pounds of coal 1,000 feet in one minute, or 1,000 pounds 33 feet in one minute. You can make up whatever combination of feet and pounds you like. As long as the product is 33,000 foot-pounds in one minute, you have a horsepower.

You can probably imagine that you would not want to load 33,000 pounds of coal in the bucket and ask the horse to move it 1 foot in a minute because the horse couldn't budge that big a load. You can probably also imagine that you would not want to put 1 pound of coal in the bucket and ask the horse to run 33,000 feet in one minute, since that translates into 375 miles per hour and horses can't run that fast. However, if you have read How a Block and Tackle Works, you know that with a block and tackle you can easily trade perceived weight for distance using an arrangement of pulleys. So you could create a block and tackle system that puts a comfortable amount of weight on the horse at a comfortable speed no matter how much weight is actually in the bucket.

Horsepower can be converted into other units as well. For example:

• 1 horsepower is equivalent to 746 watts. So if you took a 1-horsepower horse and put it on a treadmill, it could operate a generator producing a continuous 746 watts.
• 1 horsepower (over the course of an hour) is equivalent to 2,545 BTU (British thermal units). If you took that 746 watts and ran it through an electric heater for an hour, it would produce 2,545 BTU (where a BTU is the amount of energy needed to raise the temperature of 1 pound of water 1 degree F).
• One BTU is equal to 1,055 joules, or 252 gram-calories or 0.252 food Calories. Presumably, a horse producing 1 horsepower would burn 641 Calories in one hour if it were 100-percent efficient.

In this article, you'll learn all about horsepower and what it means in reference to machines.

How does a carburetor work?

If you have read the page entitled How Car Engines Work, you know that the idea behind an engine is to burn gasoline to create pressure, and then to turn the pressure into motion. A remarkably tiny amount of gasoline is needed during each combustion cycle. Something on the order of 10 milligrams of gasoline per combustion stroke is all it takes!

Car Engine Image Gallery

This is the side that connects to the engine.

The goal of a carburetor is to mix just the right amount of gasoline with air so that the engine runs properly. If there is not enough fuel mixed with the air, the engine "runs lean" and either will not run or potentially damages the engine. If there is too much fuel mixed with the air, the engine "runs rich" and either will not run (it floods), runs very smoky, runs poorly (bogs down, stalls easily), or at the very least wastes fuel. The carb is in charge of getting the mixture just right.

On new cars, fuel injection is becoming nearly universal because it provides better fuel efficiency and lower emissions. But nearly all older cars, and all small equipment like lawn mowers and chain saws, use carbs because they are simple and inexpensive.

The carburetor on a chain saw is a good example because it is so straightforward. The carb on a chain saw is simpler than most carbs because it really has only three situations that it has to cover:

• It has to work when you are trying to start the engine cold.
• It has to work when the engine is idling.
• It has to work when the engine is wide open.

No one operating a chain saw is really interested in any gradations between idle and full throttle, so incremental performance between these two extremes is not very important. In a car the many gradations are important, and this is why a car's carb is a lot more complex.

This short video of the carburetor (5.1 MB) takes you on a quick tour of the carb.

Here are the parts of a carb:

• A carburetor is essentially a tube.
• There is an adjustable plate across the tube called the throttle plate that controls how much air can flow through the tube. You can see this circular brass plate in photo 1.
• At some point in the tube there is a narrowing, called the venturi, and in this narrowing a vacuum is created. The venturi is visible in photo 2
• In this narrowing there is a hole, called a jet, that lets the vacuum draw in fuel. You can see the jet on the left side of the venturi in photo 2.