Almost every people used to drive a vehicle for their necessities as well as for neediness. Also, frequently you go off to the gas station plenty of times to fill out the fuels. Many of us noticed a different grade of petrol in the same pump with some cost variation. (same gasoline, but the expense gets varied)
Have you been thinking about it?
What is the difference, and why does the rate get varied?
First of all, to burn the fuel inside the combustion chamber (cylinder) in a spark-ignition engine, the air-fuel mixture has compressed. At the end of the compression, a spark has initiated via a spark plug to generate power by burning the compressed mixture. The same trait occurs for every single cycle for power generation.
After hours of continuous running, an engine becomes hot. So while combusting the fuel, sometimes not all the injected fuels are burned. There are several parameters involved, like, if the spark intensity is not enough for complete combustion, then the flame travel is said to be poor, so some unburned fuels are stuck. Similar to that, fuel quality, ignition timing, and mixture proportion are also inducing this occurrence. Sometimes the unburned fuels come out in exhaust, but mostly they have fused to the cylinder walls inside. Due to an increase in temperature, these impinged fuels get auto-ignited before or at the time of spark initiation. Soon after, flames from spark plug and explosion of residue fuels strike each other and extract more pressure inside the cylinder. So that an unusual vibration has generated in the cylinder. This occurrence is known as knocking or detonation or pinging sound that you heard from your engine. This pinging sound intimates that the abnormal combustion is undergoing inside the chamber.
Have you been thinking about it?
What is the difference, and why does the rate get varied?
First of all, to burn the fuel inside the combustion chamber (cylinder) in a spark-ignition engine, the air-fuel mixture has compressed. At the end of the compression, a spark has initiated via a spark plug to generate power by burning the compressed mixture. The same trait occurs for every single cycle for power generation.
After hours of continuous running, an engine becomes hot. So while combusting the fuel, sometimes not all the injected fuels are burned. There are several parameters involved, like, if the spark intensity is not enough for complete combustion, then the flame travel is said to be poor, so some unburned fuels are stuck. Similar to that, fuel quality, ignition timing, and mixture proportion are also inducing this occurrence. Sometimes the unburned fuels come out in exhaust, but mostly they have fused to the cylinder walls inside. Due to an increase in temperature, these impinged fuels get auto-ignited before or at the time of spark initiation. Soon after, flames from spark plug and explosion of residue fuels strike each other and extract more pressure inside the cylinder. So that an unusual vibration has generated in the cylinder. This occurrence is known as knocking or detonation or pinging sound that you heard from your engine. This pinging sound intimates that the abnormal combustion is undergoing inside the chamber.
As long as it gets continued, the combustion chamber has weakened, which reduces the engine's span. With that, it also minimizes efficiency and performance.
How does knocking be prevented?
Modern internal combustion engines have controlled by Electronic Control Unit (ECU) for optimizing better performance. Here, they prevent the knocking with the assistance of a knocking detection sensor located outside the cylinder block or under the intake manifold.
How does knocking be prevented?
Modern internal combustion engines have controlled by Electronic Control Unit (ECU) for optimizing better performance. Here, they prevent the knocking with the assistance of a knocking detection sensor located outside the cylinder block or under the intake manifold.
This sensor has materialized using a piezoelectric measuring element that collects data about the frequency of vibrations generated at every single power stroke and transmits data to ECU via an electrical signal. ECU syncs the fetched info with preset data. If the frequency gets deviated from the preset value, it finds that there is knocking inside.
So to avoid that, it also fetches data from the lambda sensor (measures O2 level in the exhaust), mass (air) flow sensor (measures volume of air entering in the intake manifold), injection pressure, speed, etc.,
If the acquired data are mismatched, the control unit optimized the engine by retarding the ignition timing. So knocking gets prevented.
Everything is fine, what about the fuel pricing and the difference??
So to avoid that, it also fetches data from the lambda sensor (measures O2 level in the exhaust), mass (air) flow sensor (measures volume of air entering in the intake manifold), injection pressure, speed, etc.,
If the acquired data are mismatched, the control unit optimized the engine by retarding the ignition timing. So knocking gets prevented.
Everything is fine, what about the fuel pricing and the difference??
Because in gasoline, there is an additive called octane. It increases the anti-knocking characteristics of the fuel by increasing the auto-ignition temperature. So that the chance of knocking, as well as pre-ignition, are reduced. In gas stations, these different grades depend on the octane rating. The lowest octane-rated fuel is 87, and the highest octane-rated is around 91 to 94. The premium graded petrol has a higher octane rating, and the regular graded has a lower octane rating. As per the manufacturer's claim, higher octane-rated petrol affords better performance and increases the engine's span too.
references: eia.gov
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