What do you think knock/pre-ignition is?

[Turbogixxer]

Just a honest question. What do you think it is and what is it is cause by. No research on the subject, just what you think/know it is.

This not a trick question (I swear)

[float_6969]

They are separate events. But pre-ignition is the most common cause of knock. Pre-ignition is when the mixture combusts before the firing of the spark plug (generally caused by a hot spot(s) in the combustion chamber). Knock is what happens when the mixture auto-ignites. When that happens, the burn process in the cylnder doesn't transpire as normal. Normally the spark plug ignites the mixture and then you have a single flame front that travels outwards from that location. When the mixture auto-ignites there can be multiple flame fronts, and when the collide the cylnder pressure skyrockets and can cause the "metallic" sound commonly assocated with knock.

[fanta]

Preignition is combustion before the spark event; knock is combustion caused after ignition, something about the two flame fronts colliding causing the pressure spike. Hot spots, sharp edges, low octane ratings, lean mixtures?That's how I remember it.

[float_6969]

not nessicarly, you can have knock before during or after the spark plug fires.

[Turbogixxer]

Both are on the right track.

Remember, Pre-ignition is also called surface igniton. The compression before the flame front increases its temperature, pressure and density.

If there is only one flame, how can it create knock?

OT: Fanta, you like the class?

[fanta]

OT: Fanta, you like the class?

Very much so! It ramped up from the basics to fresh ideas that I can take advantage of. The charts in the manual will definitely prove useful, much like the notes I took there.Solid information, no BS schemes, honest guy. I plan on attending the advanced course when possible.