On older engines knock can also be caused by carbon buildup. If little soot particles start to glow, they can ignite the mixture before the spark does and cause detonation and unwanted pressure waves that can kill the engine.
I don't know if it is mentioned ( I guess it is) but anyway, if you have a too hot grade sprak plug it can't dispose the heat of the combustion enough and it is going to glow / melt. This couse detonation also and burn holes in your piston..
The engine's resistance against knock depends of:
- Copression ratio:
lower compression ratio = less knock
- Combustion chamber design:
At the rb26 the squish area can be removed for more controled combustion.
On places where the flame front can't reach eaysily the unburn't mixture has a higher risc for detonation, that's why a smooth camber design is prefered above a chamber with a lot of angles > places that are harder to reach by the flame front.
- Pollishing of the combustion chamber / valves:
can give less carbon builup and thus some kind of extra knock resistance, it also reflects a bit of heat( But this is probably as long as the pollished chamber stay's clean,)
-Spark plug grade:
as mentioned above ( should always be right)
-Intake temperature:
lower intake temps give a more controled burn, water injection can reduce intake temps and detonation down.
- Boost:
Higher boost:
will give a higher end compression pressure and so the risc for detonation is bigger.
- Head gasket:
The head gasket is a weak point in the combustion chamber and is often the part that dies fisrt when the car detonates. A thin head gasket is prefered above a thick one cause you'll have a bigger weak spot and a little less ideal
combustion chamber shape.
- Fuel:
The thing that gives the fuel more resistance against knocking is the RON or MON number, the higher the number, the higher the resistance against knocking.
- Igniton timing:
The ignition advance depends of the engine's resistance against knock, the more resistance against it, the more advance you can cun, and ignition advance results in more power (roughly said)