Naturally Aspirated Modifications

Naturally Aspirated Modifications

This page is designed to help you with the modifications that are not considered basic. These modifications will usually cost a lot more, and will be harder to install but will offer more gains. Some of these modifications will be a waste of money if you do not have the supporting modifications.

Exhaust In the basic modifications page we discussed the cat back exhaust system, so that leaves headers, and a choice between a test pipe and the catalytic converter.

Headers-Headers are the pipes that flow directly out of the block to the catalytic converter. Many vehicles have small, ill-designed headers that restrict the passage of air. Replacing this will free up some power, but sometimes if the OEM headers on the car were well designed, replaced them with larger piping will reduce the velocity, taking away some torque. This modification is not for cars with turbochargers, due to the turbocharger turbine piping cutting into the primaries of the headers.

Hi Flow Catalytic Converter-This modification will replace the OEM catalytic converter with a unit that allows a more free passage of exhaust, with less platinum to collect the exhaust. Remember to keep this within perspective of your velocity and mass exhaust flow.

The Test Pipe-The test pipe is actually a replacement for the catalytic converter in your exhaust. The test pipe, in most cases, just a straight pipe with two flanges on it. Many people consider these to offer higher gains of power, but they are often louder and raspier than a hi flow catalytic converter.

Fuel In Vehicle's that fail to receive enough fuel become very prone to detonation and engine damage . If you are heavily modified, it might be a wise idea to purchase and install a air/fuel ratio gauge to insure the correct ratio. In the basic modifications page we discussed the Fuel pressure regulator, the fuel management unit, and the banjo bolt modification. In this page we will discuss the fuel pump, injectors, and the fuel rail.

Fuel Pump-There comes a certain point where the OEM fuel pump cannot deliver fuel at the desired rate, so to solve this problem you need to install an aftermarket fuel pump. Most people would suggest using an in line fuel pump. For force induction applications you will need a very strong fuel pump, that can deliver mass amounts of lph (liters per hour)

Injectors-Injectors become necessary usually in force induction vehicles and in heavily modified vehicles. Injectors allow a much larger mass of fuel to be delivered at a higher rate.

Fuel Rail-After a certain point, the OEM fuel rails fail to hold the mass amounts of fuel that are being delivered to the injectors. To do this, you will need to purchase a fuel rail that flows at a higher rate. Few people modify their cars enough to really need this modification.

Electronics and Electrical
We discussed the more basic modifications of electrical and electronic modifications, so now we are going to go through ignition upgrades, coils, alternators, and standalone systems.

Ignition Control Upgrades-Ignition control upgrades help the timing and electrical system keep up with the rest of the engine. There are quite a few different Packages you can buy, each doing something different, or doing more than one thing. Usually you will have to use a laptop or a programmer to adjust the control unit until it runs properly.

Ignition Coils-These assist the Ignition Control Packs by providing a more efficient method of transferring energy. The core automatically regulates spark intensity, delivering a hotter spark under heavy engine demand, and lower levels during low engine demand.

Stand Alone Engine Management-A stand alone management system is really only for those people who have done some extreme modifications. This would be one of the most extreme modifications that can be done to a car. This essentially replaces the car's ECU (Engine Control

Unit). This takes over full command of the way the vehicle runs, from the timing, to pretty much every sensor in the vehicle. These systems allow many aftermarket performance upgrades, and allows characteristics of the engine may be altered very easily. This modification allows you to tune your car to it's greatest potential if you know how. But the Stand Alone systems are very expensive, and require a great deal to install. They usually require a lap top computer, but some come with a programming unit.

Throttle Body There are three things that can be done with the throttle body that will significantly increase the performance of the car. Each one has different aspects, advantages and disadvantages.

Replacement-Often you can buy a larger throttle body in a complete assembly, which will allow a greater volume of air to pass through into the intake manifold. Of the three, this offers the most potential power. If you purchase a complete throttle body that is the size that you can bore the stock throttle body. If the stock throttle body has been bored to the size of the replacement, they will perform the same unless something is done to enhance the replacement. The advantage of modifying your throttle body this way is that you can bore it out since there is still material left on the edge of the throttle body, which likewise give you the choice of coning it to improve the velocity as well as the mass air flow. The bad side is, this is by far the most

expensive choice of the three. For a force induction application, the larger the mass air flow, the better.

Boring-Boring out the essentially is increasing the size of the diameter of the throttle body wall from the inlet to exit. A bored throttle body allows more air to pass through into the intake manifold just as purchasing a larger throttle body does. This will offer the largest gains unless the replacement would be larger than you can bore the stock throttle body. The problem with this is that the edge of the throttle body becomes more narrow. So unless you only mildly bore the throttle body coning it is impossible. This is less expensive than purchasing a complete throttle body, but more expensive than coning. The other down side is you will either have to purchase or create a throttle body plate since the walls of the unit are now farther away.

Coning-Coning the throttle body involves creating a taper, the inlet is larger and tapers to a smaller exit towards the butterfly. This allows air to enter the intake manifold at a higher velocity. This enhances the cars performance because the pistons no longer have to suck as hard to pull the air through the intake of the car. The air is already at a higher velocity, so slightly more air can be pulled into the pistons at each stroke. This is the cheapest of the three, but also offers the least amount of possible gains. With some practice you could also do this with a dremel and proper bits.

Intake Manifold The Intake Manifold is connected directly to the throttle body, and serves as passage way for air to travel to each cylinder. This works by creating a vacuum when the piston goes down, and the valves on the intake side of cam open to allow the air to pass. Many vehicles have aftermarket manifolds being made, that flow very efficiently. Although they are

very expensive, they leave you with a choice to port them still for more efficiency. Another modification you can do is to port the manifold. This works the same way as the throttle body. The inlets and runners are both opened up, and smoothed down to allow more air in with less obstruction. Remember, this is one of the largest factors of torque. The smaller the runner is without choking the motor, the more torque you will have. But, because they are smaller you are limiting your horsepower. You can opt to have higher torque, or higher horsepower. Velocity or mass. If you do enough research, you can find a nice medium between the two. Remember, the

intake manifold must be port matched to the heads, or they are just restricting the air passage and no gains will be made either way for the most part.

Heads

The heads usually are directly under the Intake Manifold, and above the pistons. They contain the cams. The heads have the same factors as the Intake Manifold. It can either be replaced by anaftermarket unit, or ported. Remember, the heads must be port matched to the intake manifold, or they are just restricting the air passage and no gains will be made either way for the most part.

Cams

Cams can be replaced or grinded to a more aggressive specification. This is done by changing the life of the cam, sometimes including the rockers if applicable, the duration of the intake side, the duration of the exhaust side and the lobe separation. The duration, and separation are measured in degrees, since all the way around a came is 360 degrees. Each cam that is different will perform uniquely at different rpm's, so before purchasing it would be wise to consider the rpm range with that and the other modifications you have. Not all cams are suitable for force induction applications and can often cause a rough idle.

Under drive Pulleys

Every engine uses pulleys to drive most of it's accessories. Every belt driven accessory takes away some power from the engine because it creates drag. You can counter this slightly by putting on smaller, lighter pulleys. This will slow the accessories down a considerable amount, which in turn will free up power, increase the longevity of the accessories since they do not work as hard, and increase gas mileage. The down side is, this means your accessories will be weaker. If you have even a moderately large stereo system, it might be a wise idea not to replace the alternator pulley. This modification usually requires the changing of the belt to a smaller one. Keep in mind which accessories you would prefer not to under drive by putting a smaller pulley on there. Most of the gains from this modification are purely weight loss.