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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Pimped Out Cars

Welcome to the Custom-car.us guide to pimping out your car, pimped out cars and car styling in general. This section is for the more modern pimped out car fanatic and is not so much about car performance. In fact it has almost nothing to do with engine performance and engine tuning but it has a lot to do with car customizing to make your car look as hot as it goes. Pimping out your car has a lot to do with car modification, car customization and of course, pimped out cars, even if it has nothing to do with engine power! In this section we'll discuss ways in which you can personalize and customize your car to make it stand out from the crowd. However, despite our age, we're more into customizing cars to look good with style and class rather than what we consider the vulgarity of the "pimped out cars" on M-TV's "Pimp My Ride" series.

A Pimped Out Mitsubishi Eclipse with style!

With this in mind, there are a number of simple things you can do to customize your car on the outside. These range from the simple fitting of aftermarket alloy wheels, fitting HID lights, tinting your car windows and applying stick on decals, that you can do yourself, to the more complicated fitting of front bumper kits, side skirts and rear wings. This will require a visit to the spray painter to match the color of your car. For the more adventurous, we also have the more complex fitting of scissor doors or lambo doors as some people call it, and designing of your own aero kit. This will again require a visit to the spray painter when it comes to fitting and matching your car's color; and while you're at it you might want to get a customized paint job.

But it does not stop there; you can also customize the inside by fitting sports seats or bucket seats, an aftermarket steering wheel and gear lever, as well as aftermarket instrument gages and aluminum pedals. Then of course is the ICE, a cool sound system with a pop-up DVD display or two!

However, there are two crucial things to keep in mind when customizing and pimping your car. Firstly, it's no good pimping your car in bits and pieces by slapping on piece here and another there because you will end up with a car that looks like a monstrosity. You need to have a vision of what you want to achieve with your car. You need a style or a theme that says something about yourself; it is called car styling after all. You could model your car on a muscle car theme for example or a JDM theme or even a motorsport racing team but be consistent with your theme all the way down to the detail on your dashboard, gear lever and other interior parts.

Secondly, where ever possible try to be original. Aftermarket wide body kits are great but are even better if modified with a little style to create a completely unique look. If you want to be even more original, you could fabricate your own body kit as long as it's done with style.

In the following pages we'll discuss various aspects of car customization, from fitting aftermarket alloy wheels to the more complex design, creation and installation of aero body kits. We'll also be discussing car detailing and auto detailing to keep it looking at its best.

Perhaps one day we may even discuss the fitting of those silly undercarriage neon lights and those gross looking wheel "spinners" that detract from rather than enhances the beauty of your car, but it is not on the agenda for now and we make no promises. Let's get on with our car styling and car customizing by fitting lambo doors to our ride ...

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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 2¼ inch exhaust pipe is ideal for an exhaust system for a 4-cylinder street car, but a 2½ 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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The Ignition System

A distributorless ignition system.

The ignition system is one of the most overlooked elements when it comes to engine and car tuning. Most people think that once their car modifications are done, all they need to do is get the ignition timing right and turn the ignition. But it's much more complicated than that. For one, the spark must be strong enough to ignite the air/fuel mixture. That might sound obvious, but what's not so obvious is that air molecules act as an insulator, and when you modify your car to get more air into the engine, the spark from the stock ignition system might be too weak to effectively ignite the air/fuel mixture, particularly if you're using a forced induction system. In fact poor spark quality can have as negative an effect on engine power as poor ignition timing. In addition, an air/fuel ratio of 11 parts air to 1 part fuel, which is a fuel rich mixture, is most conducive to spark ignition. However, the air/fuel ratio for the proper burning of the fuel is 14,7 parts air to 1 part fuel. Thus, the air/fuel mixture is not ideal for a spark ignition system, particularly during cold start conditions where fuel vaporization is not as effective.

Once the air/fuel mixture is ignited, the rate at which the flame passes through the combustion chamber becomes important if you want to unleash the maximum power from your engine. If the flame travels too fast, it would place too much load on the pistons, conrods and bearings; if the flame travels too slowly, not enough force would be generated to create maximum power at the wheels. There are three things that influence the rate at which the air/fuel mixture burns and the flame passes through the combustion chamber:

• The quality of the air/fuel mixture mixture
• The movement or turbulence of the air/fuel mixture in the combustion chamber
• The design of the combustion chamber

Langer discussed the air/fuel ratio when he discussed the four strokes of the internal combustion engine; we discuss the movement of the fuel mixture in the combustion chamber and the design of the combustion chamber in our section on gas flowing and cylinder heads; but in this section we'll discuss the carignition system, effective ignition timing, spark strength and quality, and techniques for modifying the ignition system to improve engine performance. As always, we'll begin with some ignition system basics ...

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Electronic Fuel Injection (EFI)

If there's one thing that's critical in a high performance engine, then it's fuel control. Think about it: the whole objective of adding a turbocharger, of installing NOS, even of installing a free flow exhaust system, is to improve fuel delivery into the combustion chamber. It is also events in the combustion chamber that can and will destroy a high performance race engine if it's not controlled properly. Here we're talking about controlling the combustion process. Now I've heard many arguments as to why sidedraft carburetors provide better performance than fuel injection and engine management, and vice versa but I always say: it's not about performance, it's about reliability and there's no better system for fuel control than electronic fuel injection. Any endurance race car from INDY Car Racing, to Formula 1, to the World Rally Championship, to the Le Mans Series uses electronic fuel injection (EFI) systems, not just for reliability but because ensuring that the correct amount of fuel is delivered under every condition, will provide the best performance.

EFI is central to engine management. It relies on an engine control unit (ECU) which processes a number of inputs from various sensors on the engine to deliver the correct amount of fuel at a particular RPM and air-flow rate/air density combination. The fuel is delivered through an injector, which is an electronically actuated solenoid valve. The amount of fuel that is delivered is dependent on the fuel pressure, which is usually a constant 30 psi above intake manifold pressure, and the pulse duration of the injector, i.e., the length of time the injector is held open.

Most EFI systems have a standard set of sensors. These include:

• The Barometric Pressure (BARO) Sensor, which provides the ECU with the atmospheric air pressure reading.
• The Engine Coolant Temperature (ECT) Sensor, which provides the ECU with the engine's current operating temperature. This is important because fuel vaporization varies for different engine temperatures. A cold engine requires more fuel while a hot engine requires less.
• The Intake Air Temperature (IAT) Sensor, which the ECU needs to take into account when determining pulse duration.
• The Mass Air Flow (MAF) Sensor, which is a tube positioned after the air filter in the air intake duct. The MAF sensor has a fine platinum wire that spans across the tube. The wire is heated by electrical current to maintain a constant temperature above ambient. The air flow past the wire cools the wire and more current is required to maintain the constant temperature. Thus, the amount of current required to maintain the constant temperature indicates the air flow rate. The air flow rate is divided by RPM to determine the pulse duration.
• The Manifold Absolute Pressure (MAP) Sensor, which uses manifold vacuum to measure engine load. An EFI system that uses a MAP sensor does not require a MAF sensor as it can use the input from the MAP sensor to determine the required pulse duration.
• The Oxygen Sensor (O₂S), which is used to measure the amount of oxygen that is not consumed during combustion. This is important for the correct operation of the catalyst converter and is used for emissions control rather than performance or economy. The O₂S is located in the exhaust system and is an after-the-fact measure of the air/fuel ratio. Too much unburnt fuel in the exhaust indicates a lean mixture while too little oxygen indicates a rich mixture.
• The Crankshaft Position (CKP) Sensor, which is important for timing purposes as it tells the ECU which spark plug to fire and which injector to open at any given point in the Otto cycle.
• The Throttle Position (TP) Sensor, which is another important sensor as the throttle position and the rate of change in the throttle position indicates the what the diver wants the car to do.

The modifications you can perform on an OEM EFI are somewhat limited because the OEM ECU is not reprogrammable. However, there are a number of things you can do to modify the EFI system without having to reprogram the ECU. You can increase the fuel pressure as this is one reading that the ECU does not take into account – it assumes the fuel pressure is a constant 30 psi above intake manifold pressure; you can intercept the pulse signal form the ECU, alter it using input from the manifold pressure and send it to the injector; you can increase the injector nozzle size; or you can increase the number of injectors. However, your best option, performance wise, is to install an aftermarket ECU. In the next few pages we'll discuss each of these options.

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Superchargers and Blowers

The centrifugal type supercharger

In general terms, a supercharger, which is also commonly known as a blower, is nothing more than a large air pump that is driven by a belt that runs off the crankshaft of an engine. Superchargers have been used on car engines for more than a century already, with the German car manufacturer, Gottlieb Daimler, being credited as the first person to patent a supercharger system for an internal combustion engine. His design was based on the twin-rotor air pump designed by the Americans, Philander and Francis Roots in 1859 and patented in 1860. The first production vehicles to use superchargers were built by Mercedes and Bentley in the 1920's.

Superchargers have become quite common in the car performance industry in recent years, and are even installed as original equipment on some new high performance cars. They have become popular because of their cost efficiency and reliability, but mainly because of their performance. Indeed, supercharging a car engine results in huge power increases between 50% and 100%, making them great for racing and car customizing. In fact, back in the 1980's, there was probably nothing that shouted 'hot rod' louder than a Chevy V8 with a large Roots supercharger sticking out through the hood. But supercharging has come a long way since the 1980's when superchargers were rather inefficient and struggled to make 3 pounds of boost. Today you can walk into any performance parts shop and order any number of efficient Roots supercharger and centrifugal supercharger kits designed specifically for your engine. And with supercharging technology being so advanced, those superchargers could easily double the horsepower of a stock car engine! That's more horsepower than you would ever need!

When people start thinking about fitting a supercharger there are usually two things that they are concerned about. First, they think that the added boost will put strain on the engine parts and will lead to engine damage; but this is not necessarily true. Engine damage is usually caused by excessive RPM but a supercharged engine will make the same amount of horsepower substantially lower RPMs than a stock engine, making high RPMs less of a necessity. The second concern is that some people think that by increasing the engine's compression, a supercharger will cause detonation in the combustion chamber. However, unlike turbochargers, most superchargers do not cause 'overboost' conditions. Superchargers are also designed to operate a boost pressures will not cause detonation, while most superchargers kits also include an intercooler to further detonation while other supercharger kits include a boost timing retard chip that retards the engine's ignition timing under high boost conditions.

A more pertinent consideration should be what supercharger to use, especially with all the different types of superchargers available these days. Choosing the best supercharger for your particular engine can be a bit of a challenge as no single supercharger can be described as "the best". All superchargers work well, and they all have their strengths and weaknesses. What you need is an idea of what you want from the supercharger and an idea of what to expect from each type of supercharger. Especially as different vehicles and different engines may benefit from one type or another; so it's important that you know what you're looking for.

There are two types of superchargers that are commonly used on an internal combustion car engine:

• Centrifugal superchargers, which are very similar to turbochargers; and
• Positive-displacement superchargers, such as the Roots supercharger and the twin-screw supercharger.

Furthermore, there are two different types of positive-displacement superchargers: the twin-screw supercharger and the Roots supercharger, but both are based on the same design principles but they use different types of lobes. Then there is also the sliding vane supercharger, which is not widely used on car engines and won't be discussed here. Of the three superchargers, the centrifugal supercharger is becoming more popular because of its compactness.

In this section we'll discuss the different types of superchargers, and what to expect from each one of them, as well as intercoolers. But we'll start as always with supercharger basics where we'll discuss how the different types of superchargers work.

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