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The Basics of Electronics
In order to understand and use electronic fuel injection systems effectively, it is necessary to have at least a basic understanding of some of the general principles of electricity and electronic devices. This will allow you to easily set up your system and will greatly aid you in troubleshooting the little gremlins that will inevitably show up somewhere in your projects. It is not necessary for you to be an engineer or have a degree in computer programming or electronics to be able to successfully navigate your way through a modern EFI system. Most are very user friendly and can be easily manipulated to get the desired results. However, it certainly helps if you know how to use the basic testing equipment and diagnostic methods to ensure your electronic components are working properly.
While most aftermarket EFI systems are fairly user friendly, it is a good idea to brush up on your “basic electronics 101” in case anything goes wrong and you need to diagnose small problems. Most fuel-injection problems can easily be solved with even just a rudimentary understanding of electricity.
This chapter will briefly cover the general principles of electricity and electronic devices, but if you wish to really dig in and grasp some of the more technical subjects, a trip to the local bookstore will provide access to any number of books covering topics from the basic principles all the way through to the most complex circuits and their functions. The subject of electricity is so broad itself that covering everything involved is well beyond the scope of this book. For now, we’ll just address the aspects that will directly relate to building and troubleshooting an EFI project.
When working with aftermarket fuel injection systems, it is helpful to have a basic knowledge of electricity and its principals. However, it isn’t required that you have a degree in electrical engineering to be able to install and use one.
Voltage
The volt is probably the most recognizable term in any discussion about electronics, though it is often misunderstood and misused. Basically, the voltage of any electrical circuit is a measurement of the electromotive force, or EMF, within that circuit. It is this force, or electrical pressure, that we are talking about. The potential amount of work that can be done in any situation depends on the amount of available force you have to get the job done with. The more work there is to accomplish during a given amount of time, the more force is required to do it. In electricity, voltage is our force. The more voltage we have, the more muscle we can flex when trying to get our mission accomplished. Technically, a volt is defined as the electromotive force that causes a current of one ampere through a resistance of one ohm.
Batteries can be used to store and create their own voltage. Technically, a volt is defined as the force that causes a current of one ampere through a resistance of one ohm.
In real life it might be easier to imagine a garden hose spraying water. The water pressure in the hose is similar to our volt. If the size of our hose stays the same and we require a higher volume of water from the hose, then we must increase the pressure. In much the same way if we increase the voltage in a circuit of constant resistance, the size of our hose in this case, we will see a corresponding increase in the current flow through the circuit. Voltage is to water pressure, what amperage is to water flow, and the resistance in ohms is comparable to the size of our garden hose. So as you can see, if you want an increase in amperage (or water flow), you either have to decrease resistance (increase hose size), or add voltage (increase water pressure). Also, amperage can and will be decreased by a drop in voltage or an increase in resistance.
Voltage, amperage, and resistance are interrelated, as we will see shortly, through a law of physics called Ohm’s law.
Amperes
Amperage, or amps, as it is most commonly called, is the measurement of the flow of electrons through a circuit; the flow of water though our garden hose, if you will. When we induce voltage into a circuit of some resistance, we cause electricity to move through the circuit. How much electricity, or how many electrons flow through the circuit, is our amperage.
The ignition coils are used to store energy and send current, or amperage, to the spark plugs. One amp is the amount of electrical flow that happens in a circuit with a resistance of one ohm when a pressure of one volt is applied to it.
One amp is measured as the amount of electrical flow that happens in a circuit with one ohm of resistance when a pressure of one volt is applied to it.
For example,
1 volt = 1 ohm x 1 amp, or V = O x A
Sometimes, the term amperage is referred to as inductance. The letter “I” is used to represent inductance or current. Likewise, at times resistance is used to refer to ohms, and is represented by the letter “R”. Using these terms, our formula would look like this: V = R x I
I find it easy to remember this formula by associating the letters with other things. So, when I need to recall how to calculate a circuit’s parameters using this particular formula, I just speak the phrase “Vermont equals Rhode Island” (V = R x I). However, I do realize that I am not the world’s most entertaining author of unique acronyms, so I would encourage you to come up with whatever phrase you find that helps you remember the formula best!
If you look back again to our garden hose, you will see that if we can fill a one gallon bucket in one minute with a one inch diameter hose at a given pressure, then in order to fill the bucket faster, we need more flow of water from the hose. To achieve this, we can either keep the pressure the same and use a bigger diameter hose, or keep the hose diameter the same and increase the pressure to push more water out. Think of amps as the gallons-per-minute rating of our hose circuit.
Voltage is similar to the water pressure inside a garden hose. Imagine a garden hose spraying water. If we increase the pressure, more water will flow through the hose. Similarly, if we increase the voltage in a circuit, we will see a corresponding increase in the current flow through the circuit.
Resistance
The technical term for the resistance of an electrical circuit is the ohm. It is defined as the amount of resistance a circuit has when a force of one volt through it produces a flow of one amp of current. In other words, if we wish to keep referring to our lowly garden hose, ohms would be the size of our hose. A smaller hose has more resistance to water flow than a larger one, so if the water pressure in the hose always remains the same, then a larger hose will have less resistance and therefore will pass more water. In the same manner, a circuit of constant voltage will pass more current as the resistance goes down and less current as the resistance (or ohms) goes up.
Ohm’s law relates all the functions of volts, amps, and ohms to each other. In an electrical circuit there is a mathematical balance between the three. They must all coexist within certain boundaries and a change in any one of these three values will always have an equal effect on at least one of the remaining two. Basically, Ohm’s law states that when resistance in a circuit changes, but the source voltage remains the same, then current flow will also change in an inverse proportion. This means if we increase the circuit’s resistance, then we will decrease the current flow by the proportional amount. Conversely, if we lower the resistance in the circuit, then we will raise the current flow by proportional amount.
A resistor like this one is capable of adding more resistance to a circuit. The technical term for the resistance of an electrical circuit is the ohm. An ohm is defined as the amount of resistance a circuit has when a force of one volt passes through it and produces a current flow of one amp.
Voltage plays a role here too, in that if we keep the resistance in a circuit the same and increase the voltage on the circuit, then the current flow will also increase. Anyone who has ever melted a wire while installing a car stereo or theft alarm can relate to this. If we have a small wire and too much voltage, then the amount of current that tries to pass over the wire will usually result in copper and plastic goo that has a wafting odor of burned popcorn!
Current passing though a circuit produces heat energy that needs to be expended. This usually occurs naturally though convection to the atmosphere, but sometimes an ECU will use a heat sink to draw heat away from it and into the atmosphere or sometimes even a fan to blow cool air on its components.
This heat that is generated is why a short to ground usually causes some kind of damage to the components in the circuit. A short circuit happens when a part of a circuit becomes damaged and results in a path of electron flow that leads directly to a ground source. Electricity always follows the path of least resistance, so if you provide a means to bypass any resistance in the circuit and go directly to ground, the electricity will gladly take it. Do you remember what happens if we lower the resistance of a circuit? That’s right, the current goes up — a lot in this case. When a short to ground occurs, the current flow gets so high that it usually produces enough heat to destroy the circuit it is traveling on. At best, it will cause the circuit to cease operation. At worst, it can potentially cause a fire if left undiscovered.
Now that we have discussed a few of the basic terms and principles of electricity, lets take a look at how these factors and the changing of them affects our fuel-injection strategy.
Many modern ECUs like this one from F.A.S.T. have built-in aluminum fins called heat sinks, which allow them to dissipate the heat generated from the internal circuitry.
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Table of Contents |
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Chap. 1 - Carburetors vs. Fuel Injection |
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Chap. 2 - The Basics of Electronics |
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Chap. 3 - Tools and Equipment |
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Chap. 4 - ECU Inputs |
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Chap. 5 - ECU Outputs |
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Chap. 6 - Tuning Maps and Basic Engine Calibration |
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Chap. 7 - ACCEL/DFI |
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Chap. 8 - AEM Plug & Play |
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Chap 9 - Autronic |
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Chap. 10 - Edelbrock Pro-Flo and Advanced Programmable Fuel-Injection Systems |
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Chap. 11 - EFI Technology |
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Chap. 12 - Eelectromotive |
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Chap. 13 - F.A.S.T |
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Chap. 14 - Haltech |
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Chap. 15 - Holley Commander 950 |
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Chap. 16 - MoTeC |
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Chap. 17 - Simple Digital Systems (SDS) |
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