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Readers who envisage to carry out similar works inspired by the below method shall do this at their own risks and liability.
What is engine knocking (super knock)?
You might not notice that your engine is knocking or pinging since not all cars will let you notice the metallic noise resulting from this combustion phenomenon. A normal explosion within a petrol ICE (Internal Combustion Engine) is supposed to occur in a controlled manner when the spark plug ignites the mixture and to spread from the spark plug electrodes towards the edges of the combustion chamber.
The engine knocking is a unwanted explosion of the fuel/air mixture resulting in multiple flames igniting simultaneously and the fuel mixture exploding in more than one place with these explosions generating mechanical shock waves which will hit each other and the combustion chamber walls as well.
This generates a metallic noise known as "pinging" or "knocking" as if you were hitting a metal part with a small and light hammer.
The engine knocking is a unwanted explosion of the fuel/air mixture resulting in multiple flames igniting simultaneously and the fuel mixture exploding in more than one place with these explosions generating mechanical shock waves which will hit each other and the combustion chamber walls as well.
This generates a metallic noise known as "pinging" or "knocking" as if you were hitting a metal part with a small and light hammer.
First symptoms of repeated engine knocking (super knock)
The first visible symptom of the knocking effect is unusual damage to the spark plugs electrodes especially the central electrode. The below deposits on the spark plugs are due to excessive oil consumption but the central electrode has almost vanished (see the one in the middle or to the left) despite these iridium spark plugs did not age for more than 20,000 km which denotes another engine problem: super knock (knocking).
Other petrol engine repeated knocking symptoms include:
- Pinging noise from time to time upon accelerating or re-accelerating
- Loss of power
- Excessive fuel consumption
- Generation of super knock codes by the OBDII system with tenths or hundreds of occurrences detected by the knock sensor
- Pre-ignition problems resulting in uneven idle, excessive engine noise and a loud explosion noise heard from time to time
- The engine does not stop precisely when turning it off
- Early and abnormal destruction of the spark plugs electrodes
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Super knock (knocking) effects on engine pistons
The below engine, a Peugeot EB2 1.2 VTi PureTech 3-cylinder engine, is showing signs of super-knock damage on the pistons. The engine is one of the latest generation high efficiency ICEs accommodating badly petrol of poor quality especially:
Fortunately, this damage does not require replacing the pistons but the presence of holes on the piston surface will unfortunately increase the chances of super knock occurrence and unevenly distribute the heat over the pistons surface.
- Low Octane rating
- High contents of sulfur
Fortunately, this damage does not require replacing the pistons but the presence of holes on the piston surface will unfortunately increase the chances of super knock occurrence and unevenly distribute the heat over the pistons surface.
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Super knock (knocking) effects on engine cylinder head
The same craters can be seen on the opposite side of the combustion chamber to the pistons, i.e. on the cylinder head. The valves being made of extremely hard material and the valves seats being inclined, it's the remaining area of the cylinder head's combustion chamber that suffers from the knocking phenomenon as shown in the below pictures:
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How to fix engine super knock (knocking)
There's not much you can do except:
- Try identifying the source of the bad gasoline and change your supply to the one that generates less knocking
- Use the highest available octane rating in your area
- Regularly add octane booster fuel additive to your fuel tank, every 10,000 Km and prior to a tank fill
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