BMW M3

BMW luxury cars have not always been popular candidates for modified car projects, but with the horse power wars between the top German car manufacturers of the last few decades, they have become quite popular with aftermarket car tuning houses such as Geiger and Reiger. As a result you'd always find the latest BMW cars, such as the BMW M3 and the other BMW 3 Series models at custom car shows.
Below is our gallery of some of the hottest BMW cars from different custom car shows...

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Chevrolet

Custom Chevrolet cars have always been one of the iconic attractions a custom car shows, especially when hotrodders started slapping a Roots type supercharger on Chevrolet muscle cars such as the Chevrolet Impala SS and the Chevrolet Camaro. Then there's also the Chevrolet Corvette a popular model on the modified car scene.

Below are some of the best custom and modified Chevrolet cars from the biggest car shows...

Custom Chevrolet Bel Air at the SEMA Show in 2008

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Performance Camshafts

The two important aspects of a camshaft, in terms of engine performance, are camshaft duration, or cam duration, and valve lift. Both cam duration and valve lift are determined by the camshaft lobe. Cam duration is the time that at least one valve of a cylinder remains open, i.e., off its valve seat, measured in degrees rotation of the crankshaft, while valve lift is the maximum distance the valve head travels from the valve seat.

VALVE LIFT

Valve lift is somewhat related to intake valve head diameter. An engine with an intake valve head diameter of 1.400in to 1.500in will generally perform best with a valve lift of 0.395in to 0.475in; an engine with a larger intake valve head diameter of 1.750in to 1.875in will generally perform best with a valve lift of 0.425in to 0.550in; and an engine with a large intake valve head diameter of 2.000in to 2.250in will generally perform best with a valve lift of 0.475in to 0.650in. But these are just rough guidelines; ultimately you will need to take some gas flow readings on a flow bench to determine the best valve lift for your particular engine.

A number of factors influence valve lift. The most important being the gap between the intake and exhaust valves, the piston to valve clearance and the intake charge pressure. These factors also influence cam duration. Another factor influencing valve lift is valve spring compression. Obviously, once the valve springs are fully compressed, it cannot give any more and the valve cannot be pushed further down into the combustion chamber.

CAM DURATION

As I've mentioned earlier, cam duration is measured in degrees rotation of the crankshaft, rather than the camshaft, and the crankshaft completes two full rotations for every rotation of the camshaft. In other words, with a 310 degree camshaft, the valves are open for only 155 degrees of actual camshaft rotation.

A performance camshaft for a naturally aspirated engine will have a duration in the range of 270 degrees to 310 degrees or more, with a 270 degree camshaft described as a 'mild' camshaft and a 310 or more degree camshaft being described as a 'wild' race camshaft. A stock camshaft usually has a duration of around 270 degrees but what differentiates a 270 degree performance camshaft from a stock camshaft is increased valve lift and a much faster rate of valve lift. With a faster valve lift rate, the valve reaches full lift quicker and remains at full lift for longer. This increases Volumetric Efficiency (VE) as more air flow in and out of the engine is possible.

A determining factor, when choosing camshaft duration is the purpose of the vehicle. The longer the duration of the camshaft, the further up the rev range the power band shifts, and the rougher the idle. Obviously, as the power band moves higher up the rev range, bottom end power is lost. Also, as cam duration and valve overlap increases, torque is lost. Fuel efficiency also decreases and exhaust emissions increase as valve overlap increases.

High performance camshafts start at 280 degrees of duration. These camshafts have increased valve overlap but not too much so emissions and fuel economy are not severely affected. These are generally good camshafts for modified street cars and produce good power from 2,500 RPM up to 7,000 RPM but they do not have a smooth idle because of the increased valve overlap.

A 290 degree camshaft requires more cylinder head work in terms of cylinder head porting and gas flowing as they work better when the engine's Volumetric Efficiency (VE) is improved. As you'd expect, these camshafts produce a fairly rough idle. These camshafts are generally good for rally cars and produce power from 3,000 RPM up to 7,500 RPM. A 300 degree camshaft requires even higher levels of VE, reaching the physical gas flowing limitations of a two valve cylinder head with a single camshaft. These camshafts are good for modified race cars and produce good power from 4,000 RPM up to 8,000 RPM. However, they have a very rough idle.

A camshaft with a duration of more than 300 degrees is an out and out race camshaft with a power band in the 4,500 RPM to 9,000 RPM rev range. To make effective use of a 300 degree camshaft, you need to ensure that the engine has a very high VE. You also need to ensure that the engine can rev beyond the red line of most stock engines.

VALVE OVERLAP

The limit for opening the exhaust valve is approximately 80� before bottom dead center (BBDC). Opening the exhaust valve any sooner tends not to increase power production but will shift the power band higher up the rev range and will reduce low end torque as downward pressure on the piston during the power stroke is released. The same applies to closing the intake valve where 80� after bottom dead center (ABDC) is the limit for increased power production.

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Dodge Challenger

Dodge is renounded for its Mopar muscle cars such as the Dodge Charger and the Dodge Challenger of the 1970s. These classic cars are quite popular at custom car shows, especially in North America. Their modern counter parts, the retro styled Dodge Charger and the Dodge Challenger of the late 2000s, as well as the hot Dodge Viper of the 1990s have also become quite popular among car tuners such as Geiger and can be seen at any car show, from SEMA in Las Vegas, to the Essen Motor Show in Germany, and even at the Tokyo Auto Salon in Japan!
We've collected pictures of some of our favorite classic Mopar Dodge muscle cars, as well as some of the more modern Dodge cars from different car shows around the world...

Classic Dodge Challenger at the 2009 Detroit International Auto Show

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Bugatti Veyron 16.4 Grand Sport

Bugatti made its reappearance after a long absence in the later 1990s under the ownership of Volkswagen AG. Since then the company has struck gold in the form of the insanely fast, 1,000 bhp Bugatti Veryron supercar which has become a favorite among tuners of exclusive cars, and a favorite among car enthusiasts.
Below is our gallery of some of the best tuned Bugatti cars from various car shows...

Bugatti Veyron 16.4 Grand Sport at the 2010 Beijing Auto Show

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BMW Z4 Coupe

BMW luxury cars have not always been popular candidates for modified car projects, but with the horse power wars between the top German car manufacturers of the last few decades, they have become quite popular with aftermarket car tuning houses such as Geiger and Reiger. As a result you'd always find the latest BMW cars, such as the BMW M3 and the other BMW 3 Series models at custom car shows.
Below is our gallery of some of the hottest BMW cars from different custom car shows...

BMW Z4 Coupe by dStyle at the 2008 Essen Motor Show

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Doing The Head

A Twin Cam Cylinder Head

When it comes to getting the most power out of a naturally aspirated engine the key area that you must focus your attention on is the cylinder head. This is the one area that will potentially give you the greatest increase in engine power. Why? Well, as Langer explains in engine building and power basics, the key to increasing an engines horse power is to get the engine to ingest more air and be able to expel the resultant increase in exhaust gasses, in other words, getting the engine to pump more air by increasing the air-flow in and out of the engine.

On a motor car engine, there are three areas that can affect air-flow and where you can make improvements. These are:

• The intake system, which includes the air filter, plenum and the intake runners.
• The exhaust system, which includes the exhaust header, catalyst converter and the mufflers.
• The cylinder head, which includes the cylinder head ports, valve area and the camshafts.

We've discussed the intake system and the exhaust system elsewhere on this web site so now it's time for us to turn our attention to modifying the cylinder head. However, in this section we're going to discuss a little bit more than just the cylinder head, we're going to discuss cylinder head porting, gas flowing and power tuning the cylinder head, old school style! We'll also be discussing performance camshafts, cam timing, valve timing and valve overlap.

A word of warning though, cylinder head porting and gas flowing is a rather advanced form of car modification and is not for the novice or for the faint of heart. Cylinder head porting is a skill that must be developed and honed by hours and hours of practice. If you're intent on trying cylinder head porting, the first thing that you need to know is the porting always begins by trial and error so if you're going to do your own cylinder head porting, start on a cylinder head that you can afford to total, in fact, start with a couple that you don't mind loosing. Otherwise you should leave cylinder head porting up to a professional with a flow bench. The other thing to note, is that cylinder head porting requires some rather expensive tools. You'll need a high-speed extended pneumatic die-grinder with carbide and steel grinders, and a high-pressure air compressor (no, we're not talking about turbochargers here) to power the grinder. You could use an electric die-grinder rather than a die-grinder, but electric die-grinders don't operate at a high-speed like pneumatic die-grinders. You could also use an electic drill rather than a die-grinder but you won't get the same results as you would with a longer, more agile and thinner die-grinder. An electric drill also does not operate at the high-speeds that a pneumatic die-grinder does.

A Pneumatic Die Grinder

Right, if you've read all that, bought your air compressor and your die-grinder, and gotten hold of a few spare cylinder heads, despite our warnings, then we can move on and start modifying the cylinder head for extreme power. But remember that we did warn you. Right, we'll begin by looking at the camshaft before moving on to the equipment you'll require to port your cylinder head, the basics of gas flowing and cylinder head porting itself.

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The Diesel Engine

The diesel engine was developed by Rudolf Diesel and was patented in 1892. Diesel engines are very similar to petrol or gasoline engines in that both rely on the Otto cycle to convert the chemical energy in fuel into mechanical energy and, in so doing, produce power. The major difference is the way fuel is delivered to the combustion chamber and the way the fuel mixture is ignited. Firstly, in gasoline engines, the fuel is usually fed into the intake manifold or the intake port where it is combined and mixed with the intake air, which is also called the intake charge. In modern diesel engines, the fuel is injected directly into the combustion chamber. This means that only the intake charge is compressed during the compression stroke and the diesel is only introduced once the intake charge has been compressed. Secondly, in gasoline engines, the fuel mixture is ignited by a sparkplug, while in diesel engines the fuel is ignited by the heat from the compressed air in the combustion chamber. However, diesel requires a much higher temperature than petrol before ignition (not spontaneous ignition) can take place.

These differences has important consequences for the modification of diesel engines, especially when you consider the differences between diesel fuel and gasoline.

THE DIFFERENCES BETWEEN DIESEL AND GASOLINE

For starters, diesel is a heavier fuel than gasoline. In other words, it contains more carbon atoms in longer chains than gasoline (technically, gasoline is typically C₉H₂₀, while diesel fuel is typically C₁₄H₃₀). Because it is heavier, diesel is much more stable that gasoline and vaporizes at a much higher temperature than gasoline. It also vaporizes much slower than gasoline and burns much slower. The result is that diesel requires a much higher temperature to ignite. Gasoline, for example can burn at temperatures of -40� F while diesel requires a temperature of at least 143� F!

The main point, however, is that diesel burns slower than petrol. This means that it will produce a steady pressure on the piston for longer. Consequently, diesel can be ignited at a higher temperature, and indeed can be allowed to reach the point at which it will ignite spontaneously. The interesting thing is that diesel needs a temperature of 410� F to ignite spontaneously but will ignite or burn at a much lower temperature of 143� F. Consequently, diesel cannot be introduced into the combustion chamber until the correct temperature is reached, or else it will pre-ignite. Now, to reach the required temperature, air in the combustion chamber must be compressed much more than in a gasoline engine, and because there is not fuel in the combustion chamber, the intake charge can be safely compressed without the danger of pre-ignition. Thus a gasoline engine will typically have the compressions ratio would of somewhere between 1:9 and 1:12 while a diesel engine will typically a compression ratio of around 1:25! And it is this higher compression ratio, as well as its higher vaporization point and slower burning rate and the fact that diesel has about 17% more energy density than gasoline, that makes diesel much more efficient than gasoline.

Now you're thinking why not use direct injection in a gasoline engine so we can increase the compress without pre-ignition? Indeed some manufacturers to employ direct injection on gasoline engines, but without the higher compression ratio because gasoline will burn too quickly at higher temperatures, hence the need to keep the temperature of the intake charge down in a gasoline engine. Remember, diesel burns at a slower rate than gasoline and therefore can be ignited at higher temperatures.

DIESEL ENGINE MODIFICATIONS

When it comes to modifying a diesel engine, you can apply the same techniques that you would apply to a gasoline engine, except for ignition system obviously as diesel engine has no spark plug. All the basics apply, i.e., increasing the engine displacement, increasing the engine speed, improving and increasing the air intake, and increasing the volumetric efficiency.

Nonetheless, there are a number of things to consider before attempting to modify a diesel engine.

• Firstly, components in the diesel engine are exposed to far higher pressures and temperatures than the components in gasoline engines. Therefore, diesel engines need to be more robust with thicker cylinder walls and stronger pistons. Should you decide to increase the displacement of your diesel engine by boring out the cylinders you should ensure that you improve your cooling system.
• Secondly, diesel burns at a much slower rate than gasoline; therefore a diesel engine will operate at a much lower RPM. This is natural, and getting the diesel engine to operate at higher speed will mean increasing the temperatures in the combustion chamber, which would require thicker cylinder wall and much a better cool system, and improving the cooling system is easier said than done because of diminishing returns!
• Furthermore, increasing the temperatures in the combustion chamber will increase the heat in the intake manifold, and will result in a reduction of air density. Consequently, we're dealing with even more diminishing returns! Still, maximum power will be reached at relatively low RPMs because of the slow rate at which diesel burns and will drop off dramatically at higher RPMs.
• Thirdly, increasing the amount of air ingested by the engine will require a proportionate increase in the amount of fuel injected into the engine. Thus bigger injectors, a higher fuel pressure will be required, or a remapped engine control unit (ECU) would be required. On some turbo-diesel engines, a remapped ECU has led to impressive improvements in power and should be the starting point in your quest to squeeze more power from a diesel engine.

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Engine Building for Power and Reliability

If you're planning to do some serious modifications to a four stroke engine, you'd better do it right if you don't want to end up with an expensive pile of scrap metal. It's easy to slap on a turbo and run mild boost on a stock engine or even fitting a bigger turbo to an OEM turbo engine, but if you're looking for serious power, you have to rebuild the subassembly to ensure that it can handle the additional power without disintegrating. Obviously you need to ensure that your drive train can handle the extra engine power as well, but in this section we'll discuss engine building for maximum power, starting with the subassembly.

THE CYLINDER BLOCK

You've got to start by ensuring that your cylinder block is race grade. Even if you're just building a street race car, engine tuning would be senseless if the block is not up to the job. Start by pressure testing the block. If you have an air compressor you can do this yourself. Strip down the engine but leave the Welch plugs and oil gallery plugs in place. Fit the bare cylinder head to the cylinder block using new head gasket or one that's not too worn. Close all water opening off with steel plates. One of the plates must be fitted with an air line fitting that you can connect your air compressor to. Gradually increase the pressure in the block to 40 psi. Don't increase the pressure too quickly as a loose fitting Welch plug or a weak spot in the block could blow out can cause you serious injury. If everything is still in place, gradually increase the pressure to 50 psi. Now spray the block with a mild water/detergent mixture. Carefully check the block for air bubbles. If you see bubbles, either have it repaired or test another block. If you get no bubbles, release the air pressure and remove the cylinder head. Use a plug tap to clean the head stud and main bearing cap threads and chamfer any stud hole that is not already chamfered. This will prevent the thread from pulling up. Grind away any casting sag, especially around the main bearing webs, the sump pan deck, and the valley area of a Vee engine. This will prevent cracks from developing. Now remove all the Welch plugs and oil gallery plugs and have the block boiled and cleaned in a chemical bath. This will remove all rust and scale in the water channels, and the caked oil in the oil galleries.

THE CRANKSHAFT & CON RODS

Chrome-moly forged con rods

The stock crankshaft and con rods are usually cast iron items that can be retained if the engine is not required to handle high boost pressures, high horse power, and high revs. Forged crankshafts and con rods are much stronger and are more suitable for high load, high rev engines. In either event, you should have the crankshaft and con rods Magnafluxed to check for cracks.

If the crankshaft has no cracks, check it for straightness. A crankshaft that is even 0.002in out of straight will increase bearing load and will be the cause of bearing failure. If your crankshaft is out of straight, you have two options � either have the crankshaft straightened or machine the crankshaft's main journals so that crankshaft rotation is true. However, straightening a crankshaft that is to be used for a high boost, high horse power, and high rev engine is a waste of time and money as the combustion pressure and inertia loads will reverse the straightening process. Machining the crankshaft journals will also weaken the crankshaft. Ultimately, replacing a bent crankshaft is your best option.

It goes without saying that all the crankshaft journals should be checked for roundness and size. The same goes for the big end on the con rods. The crankshaft, con rods, and flywheel should then be balanced statically and dynamically to reduce shock loading and vibration.

THE PISTONS

High strength forged pistons

The next thing you need to consider is the pistons. Most OEM engines are fitted with cast aluminum pistons with a slotted oil groove. High performance OEM engines may be fitted with hypereutectic cast aluminum pistons that have a higher silicon content. The higher silicon content makes the cast material much harder and more wear resistant, which allows these pistons to withstand greater temperature and pressure loads. This makes these pistons ideal for street racers. However, the higher silicon content also makes the pistons more brittle and prone to breaking under detonation. Thus, these pistons are not a good choice for forced induction applications where the possibility of detonation in greatly increased.

Forged pistons, on the other hand, have much denser and even harder than hypereutectic cast aluminum pistons but are not as prone to breaking under detonation. Forged pistons also have drilled oil holes round the oil groove rather than a slot in the oil groove. This makes them the best option for high horse power, forced induction engines.

Pistons can also be either full skirt pistons or slipper type. The full skirt pistons are heavier but stronger and less prone to wobble. Needless to say, they would be the best option for any engine modification project.

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Maximizing Engine Power

The four stroke engine.

Custom-car.us is all about engine tuning and car performance; so if you want to know about car tuning, how to increase engine power and how to modify your car, then you've come to the right place. However, before we can start talking about engine tuning and increasing engine power and torque, we first need to have a basic understanding of how an internal combustion engine produces power. Therefore, over the next few pages of this section, we'll discuss the various basic concepts and principles of the internal combustion engines and the common terms used to discuss engine modifications, such as volumetric efficiency, engine displacement and air density as all of these influence engine power and performance. We also have a glossary of car modification terms that you can check for the meaning of some of the terms we use on this site. Once we have a clear understanding of how a four stroke engine produces power, we can move on and start make our P.L.A.N.s to increase engine performance.

Although there are two types of internal combustion engines, namely the two stroke engine and the four stroke engine, we're only interested in car performance and since the two-stroke engine is not used on cars, we won't be discussing that engine here. Instead we'll focus out attentions soely on the four-stroke engine because custom-car.us is all about car tuning and because cars use the four-stroke engine and not the two-stoke engine. If you're looking for information about the two-stroke engine, you could try How Stuff Works or Wikipedia.

The Wankel rotary engine.

There are also numerous derivatives of the four stroke engine � diesel engines, petrol engines, four cylinder engines, straight sixes, boxer engines, rotary or wankel engines, turbocharged engines, supercharged engines, etc. With the marked exception of the rotary engine, all four stroke engines have a common basic design � they all consist of individual cylinders with pistons that are connected to a flywheel by a crankshaft, and they all make use of what is known as the Otto Cycle. This makes it fairly easy to discuss basic engine power concepts as we don't need to concern ourselves with V's and straights, boxers and horizontally opposed engines. Instead our discussion can and will be all about the four stroke internal combustion engine. In addition, the diesel engine has had a resurgence in recent years and has become more of a performance engine, especially the turbo-diesel engine. A lot of what we discuss here can be applied to modern diesel engines but there are some aspects of engine modification that are specific to diesel engines; for this reason we'll discuss diesel engines and diesel engine modifications on their own.

So let us begin by looking at the four strokes of the four stroke internal combustion engine otherwise known as the Otto cycle. You can skip this section if you're already familiar with the Otto cycle and head on over to basic engine power or engine building, but this section does tie into most of what we discuss on Custom-car.us. If you're intereseted in modifying diesel engines, hop on over to our page on diesel engines to find out how to apply our discussions to diesel engines.

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Toyota Camry

The Toyota Camry was originally launched in Japan in January 1980 as the Toyota Celica Camry. It was in essence a second-generation Toyota Carina with updated body-styling and a front-end that resembled the Toyota Celica Supra of 1978. In 1982, the Toyota Camry became a compact mid-sized sedan and hatchback model range on its own and was marketed above the Toyota Carina and the Toyota Corona, which were also a compact mid-sized model ranges. In 1986 a Camry station wagon was added to the line up while the five-door hatchback was dropped and in 1994 a two-door Toyota Camry coup� was added. The Toyota Camry is currently in its seventh generation, which was introduced at the North American International Auto Show in 2006. The latest generation includes the Toyota Camry Hybrid which went on sale in March 2006 as a 2007 model. Below are some of our Toyota Camry Wallpaper that you can download.

2009 Toyota Camry Available resolutions: 800x600 , 1024x768 , 1152x864 , 1280x800 , 1280x960 , 1280x1024 , 1440x900 , 1600x1200 , 1680x1050 , 1920x1200 [ Image Credits: � Toyota ]

2009 Toyota Camry Available resolutions: 800x600 , 1024x768 , 1152x864 , 1280x800 , 1280x960 , 1280x1024 , 1440x900 , 1600x1200 , 1680x1050 , 1920x1200 [ Image Credits: � Toyota ]

2009 Toyota Camry Available resolutions: 800x600 , 1024x768 , 1152x864 , 1280x800 , 1280x960 , 1280x1024 , 1440x900 , 1600x1200 , 1680x1050 , 1920x1200 [ Image Credits: � Toyota ]

Toyota Camry Hybrid Available resolutions: 800x600 , 1024x768 , 1152x864 , 1280x800 , 1280x960 , 1280x1024 , 1440x900 , 1600x1200 , 1680x1050 , 1920x1200 [ Image Credits: � Toyota ]

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Toyota

Like the other big Japanese car manufacturers, Toyota has been a popular candidate for car modification and show car projects. At any show car event you wouldn't just expect to see a modified Toyota Supa but also modified Toyota Carolla and Toyota Aristo cars. These days you can even expect to see a custom Toyota Prius Hybrid or two!

Below are some of the coolest Toyota show cars from around the world...

Toyota Carolla

Toyota Carolla rally car at the 2008 Sydney Motor Show

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Porsche Boxster

The Porsche Boxster is a mid-engined sports car that was designed as a roadster. It was first introduced late in 1996 and shares various components with the Porsche 911, including the hood, front wings and the head lights. A second-generation Porsche Boxster was introduced in 2005. Below are some of our Porsche Boxster Wallpaper that you can download.

2003 Porsche Boxter Available resolutions: 800x600 , 1024x768 , 1152x864 , 1280x768 , 1280x800 , 1280x960 , 1280x1024 , 1440x900 , 1600x1200 , 1680x1050 [ Image Credits: � Porsche ]

2003 Porsche Boxter Available resolutions: 1024x768 , 1152x864 , 1280x768 , 1280x800 , 1280x960 , 1440x900 , 1600x1200 , 1680x1050 , 800x600 [ Image Credits: � Porsche ]

2003 Porsche Boxter Available resolutions: 800x600 , 1024x768 , 1152x864 , 1280x768 , 1280x800 , 1280x960 , 1440x900 , 1600x1200 , 1680x1050 [ Image Credits: � Porsche ]

2007 Porsche Boxter Available resolutions: 800x600 , 1024x768 , 1152x864 , 1280x768 , 1280x800 , 1280x960 , 1280x1024 , 1440x900 , 1600x1200 , 1680x1050 , 1920x1200 , 1920x1440 [ Image Credits: � Porsche ]

2007 Porsche Boxter Available resolutions: 800x600 , 1024x768 , 1152x864 , 1280x768 , 1280x800 , 1280x960 , 1280x1024 , 1440x900 , 1600x1200 , 1680x1050 [ Image Credits: � Porsche ]

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BMW M3

BMW luxury cars have not always been popular candidates for modified car projects, but with the horse power wars between the top German car manufacturers of the last few decades, they have become quite popular with aftermarket car tuning houses such as Geiger and Reiger. As a result you'd always find the latest BMW cars, such as the BMW M3 and the other BMW 3 Series models at custom car shows.

Below is our gallery of some of the hottest BMW cars from different custom car shows...

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BMW M3

BMW luxury cars have not always been popular candidates for modified car projects, but with the horse power wars between the top German car manufacturers of the last few decades, they have become quite popular with aftermarket car tuning houses such as Geiger and Reiger. As a result you'd always find the latest BMW cars, such as the BMW M3 and the other BMW 3 Series models at custom car shows.

Below is our gallery of some of the hottest BMW cars from different custom car shows...

Widebody BMW M3 E92 by Studie AG at the 2009 Tokyo Auto Salon

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BMW 325

BMW luxury cars have not always been popular candidates for modified car projects, but with the horse power wars between the top German car manufacturers of the last few decades, they have become quite popular with aftermarket car tuning houses such as Geiger and Reiger. As a result you'd always find the latest BMW cars, such as the BMW M3 and the other BMW 3 Series models at custom car shows.

Below is our gallery of some of the hottest BMW cars from different custom car shows...

Custom BMW 325 at the Motion Custom Car Show in 2009

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Audi

Audi and the Audi TT have long been a firm favorite for car tuners from Europe and especially Germany. Of late the Audi R8 supercar has also began to garner attention, with some of the best tuners displaying their version of the Audi R8 at various custom car shows, including Germany's own Essen Motor Show. Audi cars are also popular at the SEMA Show in Las Vegas, Nevada and at the Tokyo Auto Salon in Japan.

Below is our gallery of some of the best modified Audi cars from the different car shows...

Audi A3 Custom paint on a modified Audi A3 at the 2008 Essen Auto Show

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Toyota Corolla

The Toyota Corolla is the longest running production car in the world, having been continuously produced since its release in Japan in 1966. The first Toyota Corolla came to the U.S. in 1968 as a small two-door coupe, four-door sedan and two-door wagon with a 60 hp 1100 cc engine. Unfortunately, the original Toyota Corolla was too small and underpowered for American tastes and has consequently undergone several major redesigns in subsequent years, becoming larger and more powerful. Several models were added to the Corolla line up, including the sporty Corolla Sprinter and Corolla Liftback. A compact MPV version, named the Corolla Verso, was added to the Corolla line up in 2004. The latest generation, the tenth-generation, of Toyota Corolla was introduced in 2008 as a 2009 model range. Below are some of our Toyota Corolla Wallpaper that you can download.

Toyota Corolla S Available resolutions: 800x600 , 1024x768 , 1152x864 , 1280x800 , 1280x960 , 1280x1024 , 1440x900 , 1600x1200 , 1680x1050 , 1920x1200 [ Image Credits: � Toyota ]

Toyota Corolla S3 Available resolutions: 800x600 , 1024x768 , 1152x864 , 1280x800 , 1280x960 , 1280x1024 , 1440x900 , 1600x1200 , 1680x1050 , 1920x1200 [ Image Credits: � Toyota ]

Toyota Corolla S3 Available resolutions: 800x600 , 1024x768 , 1152x864 , 1280x800 , 1280x960 , 1280x1024 , 1440x900 , 1600x1200 , 1680x1050 , 1920x1200 [ Image Credits: � Toyota ]

Toyota Corolla S3 Available resolutions: 800x600 , 1024x768 , 1152x864 , 1280x800 , 1280x960 , 1280x1024 , 1440x900 , 1600x1200 , 1680x1050 , 1920x1200 [ Image Credits: � Toyota ]

Toyota Corolla Verso Available resolutions: 800x600 , 1024x768 , 1152x864 , 1280x800 , 1280x960 , 1280x1024 , 1440x900 , 1600x1200 , 1680x1050 , 1920x1200 [ Image Credits: � Toyota ]

Toyota Corolla XRS Available resolutions: 800x600 , 1024x768 , 1152x864 , 1280x800 , 1280x960 , 1280x1024 , 1440x900 , 1600x1200 , 1680x1050 , 1920x1200 [ Image Credits: � Toyota ]

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Modified Car Safety

A 5-point harness is much better than a stock seat belt.

One of the most important aspects of car modification is ensuring that your car can be used safely on public roads. Unfortunately, this is often one of the most overlooked aspects of modifying your car. A modified street car must be safe not only for you as the drivers, and your passengers, but it must also be safe for other road users, including pedestrians. In fact, once you decide to modify your car you need to take responsibility for the safety of other road users that you may come into contact with whether you're in the right or not. Remember a motor car can easily be used as a murder weapon and by modifying your car; you're turning it into a more lethal weapon. Therefore you need to use your car responsibly and take responsibility for the consequences of your actions, which begins with improving your car's safety.

There are four important aspects of car safety that you need to take into consideration when modifying your car:

• Car handling, which we cover in suspension tuning.
• Car grip, which is dependent on the condition of your tires and suspension.
• Car brakes.
• Car restraints, such as seat belts and roll cages.

Another important aspect of car safety is driver awareness and developing a responsible driving style, which boils down to being alert on the road and driving responsibly. You can also improve your driving by taking advanced driving classes, more so if you're intent on modifying your car, though an advanced driving class is not a license to drive recklessly on public roads.

On the car itself, the two most critical elements of car safety are undoubtedly the brake system and the tires. The car brakes can only be as effective as the car's grip allows it to be, and the tires are responsible to the car's grip. Furthermore, a large proportion of the forces responsible for accelerating and decelerating the car, as well as the forces and torques that provide the control and stability of the car act on the tires, and are dependent on the grip provided by the tires. For this reason we thought it best to discuss upgrading the tires and shock absorbers in this section on car safety, although we do discuss tires and shock absorbers in our section on suspension tuning. In this section, we will thus discuss improving car safety through upgrading your brakes and upgrading your tires.

However, there are two other areas of car safety that we need to consider: roll cages and seat belts. Roll cages are essential on race cars, for obvious reasons but they are not legal on road cars in some states. If they are legal in your state, fitting a roll cage would be a highly recommended safety mechanism for drivers and passengers but they do not protect other road users and do not absolve you from driving responsibly. If you are going to fit a roll cage, you should have it built and installed by a qualified professional.

Improving your seat belts, on the other hand, can be done yourself. A four- or five-point harness is more effective than the standard two-point harness that is used on standard cars. However, fitting a four- or five-point harness often requires fitting an aftermarket seat that makes provision for two shoulder straps, and requires secure multi-point mounting. Fitting aftermarket bucket seats is covered in our section on car styling so we won't repeat that here. Instead we'll start with upgrading your tires and shock absorbers ...

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Designing and Building an Exhaust System

A performance muffler

The main purpose of an exhaust system is undoubtedly to route the spent exhaust gas out of the car's engine. Along the way the exhaust gasses may be used to drive a turbocharger and now-a-days it will most definitely incorporate a catalyst converter to reduce carbon dioxide emissions. But on a high performance car, such as a modified street car, or a modified race car, the exhaust system is much more important as it has a direct affect on engine performance and engine power. As a result, the exhaust system, and particularly the exhaust header design, plays an important part in both engine tuning and car tuning.

In general terms, an exhaust system consists of an exhaust manifold (which is sometimes called an exhaust header), a front pipe, a catalyst converter, a main muffler or silencer, and a tail pipe with an exhaust tip. In terms of tuning the exhaust system, the muffler is the easiest to deal with it's simply a matter of replacing the stock muffler with a free-flow or high performance muffler, such as a Flowmaster muffler. The result is a free flow exhaust system. However, the performance muffler must have an inlet and an outlet pipe that is the same size (diameter) as your front pipe and your tail pipe. Your front pipe and your tail pipe should also have the same diameter. The rest of the exhaust system is much more complicated as you need consider back pressure, your engine's power band, and your engine's maximum usable RPM.

BACK PRESSURE

The amount of back pressure produced by the exhaust system is crucial as too much back pressure will have a negative effect on your engine's top-end performance as it will restrict the flow rate of the exhaust gasses at high RPM. The result would be the engine not being able to expel the spent exhaust gasses fast enough to prevent spent exhaust gasses from contaminating the fresh air/fuel mixture that is drawn into the engine on the next intake stroke. Ultimately, this will result in reduced engine power! Therefore, attaching a little 1-inch pea-shooter to your engine instead of an exhaust system is not such a good idea! But then neither is fitting a 10-inch sewage pipe. If the exhaust pipe is too large, you will get reduced flow velocity of the exhaust gasses. The flow velocity of the exhaust gasses assists with the scavenging of the spent exhaust gasses as well as the amount of air/fuel mixture that can be drawn into the combustion chamber on the next intake stroke. This is because the flow velocity of the exhaust creates a low pressure immediately behind it that sucks more gasses out of the combustion chamber. The trick is thus to get the back pressure just right.

BASIC DESIGN

Our exhaust header design page will have more specific information, but generally speaking, a 2� inch exhaust pipe is ideal for an exhaust system for a 4-cylinder street car, but a 2� inch exhaust pipe is a better fit for a 6-cylinder street car. However, a 2000cc 4-cylinder modified race car would do much better with a 3-inch exhaust pipe! The size of the exhaust header primary pipes is also important as it influences both back pressure and flow velocity; while the length of the primary pipes affect the power band of your engine. The size and length of the primary pipes of the exhaust manifold, as well as your exhaust header design depends on your engine's displacement and maximum usable RPM, as well as the power band you want from the engine.

In our next section we take a closer look at ideal primary pipe length and diameter of the exhaust manifold, at the exhaust header design and at anti-reversion techniques.

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The Air Intake System

A cold air induction system.

The whole point of performance tuning and engine modifications, whether it involves supercharging, turbocharging, NOS, or gas flowing the cylinder head is to improve the efficiency of the air flow in and out of the engine. This process is often described as improving engine breathing. The main aim in improving engine breathing, is to identify restrictions that impede the air flow in and out the engine, eliminate these restrictions and improve air flow, or use a pump to force more air into the engine. Our sections on Turbochargers, Superchargers and NOS dealt with forced induction and getting more air into the engine, while our section on Exhaust Systems dealt with getting air efficiently out of the engine through the correctly tuning and designing the exhaust system.

In this section we'll discuss the air intake side of the engine and ways in which we can improve the efficiency of the air flow into the engine. We'll look specifically at improving the efficiency of the air filter and air filter box, sizing and positioning of the mass air-flow sensor and the throttle body, improving the inlet ducting, cold air induction, how to tune the intake manifold runners and how to design the intake manifold. The information discussed here is meant for naturally aspirated engines but it may also be applied to engines that use forced induction systems. Let's begin with the air filter ...

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