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What is Petrol?

Petrol is a volatile liquid primarily used as a fuel in internal combustion engines (ICE).
How is Petrol Made?
Petrol is extracted from the Earth’s crust as crude oil. This is heated in a distillation process. Different hydrocarbons are separated based on their boiling points. Then large hydrocarbon molecules are broken down into smaller, more useful ones. This molecular structure of hydrocarbons is altered to improve performance. Then various hydrocarbons are blended to create petrol for use in cars.
After refinement additives are mixed into the petrol. Some to keep engines clean by preventing deposit build-up. The additives protect the fuel system components from rust and corrosion. Oxygenates are added to improve combustion efficiency, which reduce emissions. Octane Enhancers are added to prevent engine knocking by increasing the fuel’s octane rating.
Octane Rating
The octane rating is a measure of the performance or anti-knock properties of petrol. It indicates the fuel’s ability to resist knocking or pre-ignition in an internal combustion engine. The octane rating is typically expressed as numbers such as 91, 95, or 98, with higher numbers indicating greater resistance to knocking. High-performance engines require higher octane ratings to operate efficiently and prevent engine damage.
Engine Knocking
Engine knocking, also known as detonation, is an undesirable combustion phenomenon in an internal combustion engine. It is characterised by a knocking or pinging sound that occurs when the air-fuel mixture in the engine’s cylinders ignites spontaneously or prematurely. Uncontrolled combustion can occur as early as 2 nanoseconds, well out of the manufacturer’s specification, potentially resulting in catastrophic damage to the pistons. Controlled combustion ensures a smooth-running, efficient engine.
Uncontrolled combustion can be as early as 2 nano seconds, well out of the manufacturer’s specification which can result in catastrophic damage to the pistons
Controlled combustion ensures a smooth running efficient engine.

Some petrol brands burn cleaner than others, depending on the manufacturer’s formulation. High-quality petrol often contains superior detergents and other additives that reduce carbon build-up and deposits in the engine.
These cleaner-burning fuels leave fewer carbon deposits in the combustion chamber. These carbon deposits buildup in the combustion chamber and can create hot spots and lead to uncontrolled ignition, causing knocking. High engine temperatures can cause the air-fuel mixture to ignite prematurely, resulting in knocking.
Engine knocking can reduce engine efficiency, power output, and even cause engine damage if not addressed promptly. It is essential to use the correct fuel, maintain proper engine temperatures, and ensure the ignition system is functioning correctly to prevent engine knocking.
Using higher octane petrol in an internal combustion engine (ICE) car depends largely on the engine’s design and manufacturer’s recommendations. High-performance or turbocharged engines are designed to run on high-octane fuel to prevent knocking and to optimize performance One should always refer to your car’s manual.
Engines designed for higher octane fuel, you will notice better acceleration and overall performance. High-octane petrol is beneficial and necessary for specific vehicles.
The timing of when you fill up your petrol tank is important. Running your tank too low can cause the fuel pump to overheat as it relies on fuel for cooling and lubrication. Over time, sediments can settle at the bottom of the tank. Running low might increase the chance of these particles being sucked into the fuel pump and engine.
The octane level of petrol, which indicates its resistance to knocking or pinging during combustion, is tested using specific standardized methods:
Research Octane Number (RON)
The RON is determined by comparing the fuel’s performance in a test engine under standardized conditions to a mixture of iso-octane (which resists knocking) and n-heptane (which knocks easily).
The Cooperative Fuels Research (CFR) engine is used.
The fuel is burned in the CFR engine, and its performance is measured against various reference fuels. Adjustments are made to the engine to find the point at which knocking occurs, and the percentage of iso-octane in the fuel mixture at this point gives the RON.
The Motor Octane Number (MON)
This method also uses the CFR engine but under more severe conditions (higher temperatures and engine speeds) than the RON test.
The MON test runs the engine at a higher RPM and intake air temperature. The process of adjusting and measuring is similar to the RON test, but the harsher conditions typically result in a lower number.
For truly accurate and standardized testing, the RON and MON methods are used, particularly with the CFR engine under controlled conditions. These methods are recognized by international standards and provide reliable measurements for determining the octane level of petrol.
The electrical signal produced by the knock sensor is sent to the vehicle’s ECU.
The ECU analyzes the signal to determine if knocking is occurring. The frequency and amplitude of the signal help identify the severity and nature of the knocking.
When knocking is detected, the ECU adjusts the ignition timing to prevent premature combustion. This typically involves retarding the timing (delaying the spark) to reduce knocking.
The ECU may also adjust the fuel mixture by altering the air-fuel ratio to prevent knocking.
The ECU continuously monitors the knock sensor signal to optimize engine performance and prevent knocking in real-time.Importance of the Knock Sensor
By detecting and correcting knocking, the knock sensor helps protect the engine from damage caused by high pressure and temperature spikes. This Continuous monitoring and adjustments ensure the engine operates efficiently, maintaining power output and fuel economy.
A knock sensor is a critical and essential component in modern engines designed to detect engine knocking (detonation) and help the engine control unit (ECU) make adjustments to prevent it. Here’s a detailed explanation of what a knock sensor is and how it works:

What is a Knock Sensor?
A knock sensor is a piezoelectric device that converts the vibrations and noise caused by engine knocking into an electrical signal, which is then interpreted by the engine control unit (ECU). It is typically mounted on the engine block, cylinder head, or intake manifold. The knock sensor detects specific vibrations and noise frequencies that are characteristic of engine knocking. These vibrations occur when the air-fuel mixture in the cylinder ignites unevenly, causing shock waves. The electrical signal produced by the knock sensor is sent to the vehicle’s ECU. The ECU analyzes the signal to determine if knocking is occurring. The frequency and amplitude of the signal help identify the severity and nature of the knocking. If knocking is detected, the ECU adjusts the ignition timing to prevent premature combustion. This typically involves retarding the timing (delaying the spark) to reduce knocking. The ECU may also adjust the fuel mixture by altering the air-fuel ratio to prevent knocking.
Scan for Error Codes use an OBD-II scanner to check for any diagnostic trouble codes (DTCs) that might indicate issues related to engine knocking.
Engine knocking can manifest in several symptoms such as unusual noises, decreased performance, and poor fuel economy. Diagnosing the issue involves a combination of auditory checks, fuel quality inspections, sensor testing, timing verification, fuel system examination, compression testing, visual inspections, and scanning for error codes. Prompt diagnostics and repairs can prevent long-term engine damage and ensure efficient performance.
Engine codes, also known as Diagnostic Trouble Codes (DTCs), can help identify issues related to engine knocking. While there isn’t a specific code uniquely dedicated to engine knocking, several codes can indicate conditions that may contribute to, or be the result of, knocking. Here are some common ones:
Common DTCs Indicating Knocking Issues
P0324 – Knock Control System Error. General trouble with the knock control system.
P0325 to P0334 – Knock Sensor Circuit Malfunctions
P0325 : Knock Sensor 1 Circuit Malfunction (Bank 1 or Single Sensor)
P0326 : Knock Sensor 1 Circuit Range/Performance
P0327 : Knock Sensor 1 Circuit Low Input
P0328 : Knock Sensor 1 Circuit High Input
P0329 : Knock Sensor 1 Circuit Intermittent
P0330 : Knock Sensor 2 Circuit Malfunction (Bank 2)
P0331 : Knock Sensor 2 Circuit Range/Performance
P0332 : Knock Sensor 2 Circuit Low Input
P0333 : Knock Sensor 2 Circuit High Input
P0334 : Knock Sensor 2 Circuit Intermittent
P0171 and P0174 – System Too Lean
P0171 : System Too Lean (Bank 1)
P0174 : System Too Lean (Bank 2)
These codes indicate that the air-fuel mixture is too lean, which can lead to knocking.
P0300 to P0308 – Cylinder Misfire Detected
P0300 : Random/Multiple Cylinder Misfire Detected
P0301 : Cylinder 1 Misfire Detected
P0302 : Cylinder 2 Misfire Detected
P0303 : Cylinder 3 Misfire Detected
P0304 : Cylinder 4 Misfire Detected
P0305 : Cylinder 5 Misfire Detected
P0306 : Cylinder 6 Misfire Detected
P0307 : Cylinder 7 Misfire Detected
P0308 : Cylinder 8 Misfire Detected
Misfires can cause or be caused by knocking and combustion inefficiencies.
P0420 and P0430 – Catalyst System Efficiency Below Threshold
P0420 : Catalyst System Efficiency Below Threshold (Bank 1)
P0430 : Catalyst System Efficiency Below Threshold (Bank 2)
Indicate issues with the catalytic converter, often stemming from or contributing to improper combustion, which may cause knocking.
P0101 to P0107 – Mass Air Flow (MAF) Sensor Issues
P0101 : MAF Sensor Circuit Range/Performance
P0102 : MAF Sensor Circuit Low Input
P0103 : MAF Sensor Circuit High Input
P0104 : MAF Sensor Circuit Intermittent
Issues with the MAF sensor can lead to incorrect air-fuel mixtures, contributing to knocking.
Professional Help:
Due to the complexity and various reasons that knocking can occur individually or in concert with other faults this remedial work should only by a qualified experienced technician who is proficient in this type of work.
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