It's easy to take automobiles for granted - keep some gas in the car, turn your key to start and you're all set, right? But the modern convenience of planes, trains and automobiles relies on a complex system of parts set in motion by the ignition system. How much do you know about the principles and engineering that make your ride get up and go?
What do you call the mechanism you insert your key into to start a car?
Turning your key in the ignition initiates a chain reaction to get your car started. Typically, your key turns a lock which then allows power to flow from the battery to other ignition components and accessory features like air conditioning and radio.
What material is ignited by a vehicle's ignition system?
Ignition occurs in the combustion chamber, where there is significant concentration of evaporated gasoline (and/or ethanol). The liquid itself does not serve as the burning medium.
What is the purpose of the ignition system?
The job of a car's ignition system is to provide the spark that ignites the mix of air and fuel in a car's engine. Once ignition is successfully accomplished, the engine can burn fuel and provide the energy needed to drive.
What is the minumum voltage that an ignition system needs to create to start your car?
The spark has to have enough energy to jump through the air (called arcing) from one end of the spark plug to the other. Some cars produce 50,000 volts and up to accomplish a clean ignition, but 20,000 volts will do the job in most cases.
What is the most common car battery size (voltage)?
Even though it takes at least 20,000 V to start a car's engine, that's way too much voltage to store in a car battery! Most cars use a standard 12.6 V and the current is transformed to meet the needs of ignition.
Which of the following ignition systems was popular before the 1970s?
MIS was the first type of ignition system used in vehicles, but fell out of popularity with the rise of the EIS and DIS, which are considerably more reliable and efficient alternatives.
When does the spark need to arc for the engine to start and run successfully?
Engine pistons rotate through four phases - intake, compression, combustion, and exhaust. The spark needs to occur during the compression phase to maximize energy release during the combustion phase.
What is the primary purpose of the ignition coil?
The ignition coil is a small transformer that steps up voltage from the 12 V battery so that it can ignite a combustion reaction in the engine. Electricity from the car battery travels through the coil's many wire loops to increase in voltage.
What type of current is used for automobiles?
All cars use direct current in the ignition system and other electrically powered features, such as the radio and lights. The metal frame of the car acts as ground and returns the current to the car's negative battery terminal.
How is a DIS (distributorless ignition system) controlled?
A DIS is so efficient in part because the computer is able to control ignition spark timing much more accurately than previous methods. It's also easier to maintain.
Which component of a mechanical ignition system controlled spark timing?
Turning the key in the ignition switch allows electricity to flow from the battery through a resistor to the distributor, which is responsible for timing the ignition spark. It sends the spark to the correct cylinder at the correct moment, using the magnetic field created by moving current.
Why does the key need to be turned to the "run" position after successful ignition?
During ignition, full battery power is needed for "cranking" the engine and igniting a spark. After ignition, all of the battery's power is passed through a resistor that steps down voltage for the car's other systems.
What is the benefit of having a car in which the primary resistor is housed in the firewall?
Many manufacturers choose to position the primary resistor on a car's firewall because it's a simple fix if the resistor fails. Other manufacturers use a wiring harness that makes it more difficult to replace, but also improves the longevity of the part.
During the life of a vehicle, only one type of part in a DIS (distributionless ignition system) usually needs to be replaced. Which part?
Only the spark plugs need to be routinely replaced, and even those frequently last for the first 100,000 miles or more. The computerized system has fewer components and usually they won't need to be replaced.
The faster the engine speed...
If the engine is running at a faster speed, then the spark needs to happen earlier so that there is enough time for ignition to take place before the combustion stroke!
Which of the following was used to adjust spark timing in mechanical ignition systems?
The centrifugal advance adjusted timing using weights exposed to centrifugal force from the spinning shaft. Vacuum advance relied on the near-vacuum conditions created in the combustion chamber. Both were used to increase fuel efficiency.
What happens when the thick layer of insulation around spark plug wires begins to crack and thin out?
Spark plug wires are more insulation than not, but over time the insulation will wear down. When this happens, the voltage traveling through the wire can degrade and cause the affected cylinder to misfire.
How many spark plugs are there in a V8 engine?
There are eight spark plugs - hence the name, V8. Interestingly, they don't always fire in order, and may rotate either clockwise or counterclockwise, depending on the make and model.
When a rotor spins, how many contacts does it touch?
The rotor briefly touches the contact for each of the engine's cylinders, allowing electricity to move from the coil to the cylinder's contact point.
Where are the spark plugs located?
Spark plugs are embedded in the distributor cap, allowing them to rotate either clockwise or counterclockwise to service the engine's cylinders.
What metal is used for the wiring in an ignition system?
While silver and copper are both excellent conductors, copper is less expensive and highly durable. So, automobiles, along with many other common electronics, use copper wires. Carbon is also often used.
In an mechanical ignition system (MIS), what allows electricity to get through from the ignition coil to create a spark?
A contact point in the distributor is open or closed, depending on whether the magnetic field from the coil is large or small. It's timed by the rotating distributor shaft and cam.
Where does electricity go when a point is closed?
Current won't reverse its path or stop in place, so an alternate path must be provided when the route to a spark plug through the point is closed. Distributors are constructed so that the current can flow to ground until the point is open.
What improvements did the use of an EIS introduce?
EIS allowed the ignition voltage to increase from 20,000 volts to numbers around 50,000 volts, making ignition more consistent. The new components also required less maintenance.
What mechanical component is eliminated in distributorless ignition systems?
A DIS does not require a distributor and the many mechanical parts (like points, etc.) that come with it. Everything is automated and computer controlled.
How are coils typically arranged in distributorless ignition systems?
Most distributorless ignition systems have coils arranged in packs of three, although some also have them mounted to each individual spark plug. It will cause multiple plugs to fire at the same time.
What separates the center electrode and the ground electrode of a spark plug?
In order to get a spark, it's necessary for the electricity traveling through the plug to jump from the center electrode to the ground electrode, igniting the surrounding atmosphere in the process. It's only possible because the electricity is attracted to the ground electrode, and the open air is the shortest path to get there.
By what alternate name is a distributorless ignition system (DIS) known?
A distributorless ignition system is also known as a "direct ignition system" because of its construction. Higher voltages are in direct contact with the coils, which in turn are in direct contact with the spark plugs.
What remains as the primary signalling method for timing in DIS?
Magnetism is what allows the components of a DIS to function in a timely manner, but an electronic sensor instead of a mechanical contraption responds to the magnetic fields created inside the vehicle .
Which of the following adjustments to the ignition system results in lower emissions?
Operating at a lower temperature reduces nitrogen oxide emissions, and keeping the ignition spark as close to combustion stroke as possible reduces the overall car emissions.
What component of the spark plug keeps the spark from arcing before it reaches the tip of the plug?
The ceramic insulator prevents the electric current from diverting to the metal parts of the plug, thereby ensuring that it reaches the end of the plug and arcs as needed.
What do we call the computer that controls distributorless ignition systems?
The Engine Control Unit, or ECU, controls the spark plug timing. Typically, it organizes the transistors which then control the sparks. It's also known as an EMS, or Engine Management System.
While a failed ignition is not dangerous for a car, it can be extremely dangerous for...
Rockets have very little tolerance for failed ignition because the gas build-up created can cause an explosion. Most rockets have several countermeasures to prevent explosions if a failed ignition occurs.
In mechanical systems, can all cylinders start at once?
Mechanical systems must stagger ignition for each cylinder. The timing and order is determined by the distributor and how the car was manufactured.
Why won't a car start if its battery is dead?
The battery is the car's only source of power until ignition is complete. If the battery's power is completely drained, there is no way to start a car without charging or replacing the battery.
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