Motor Knock

[highvan]

I think i have an idea, but what is motor knock? And how can you tell when it's happening?

 

[JayRolla]

I think you mean detonation(knock)

Detonation is the spontaneous combustion of the end-gas (remaining fuel/air mixture) in the chamber. It always occurs after normal combustion is initiated by the spark plug. The initial combustion at the spark plug is followed by a normal combustion burn. For some reason, likely heat and pressure, the end gas in the chamber spontaneously combusts.

You need a logger, dsmlink or some type of eprom chip to see it.

 

[Ultimatedsm]

The actual knocking noise in the motor? Or the knock count your ECU detects. If its the actual motor, it could be a ton of things, rod bearing being one of them. The ECU knock is sensed by the knock sensor in the back of the engine and it detects any kind of pinging or detenation due to abnormal conditions in the engine. For example, if your engine runs too lean, it will start to ping. The pinging will be detected by the knock sensor and than your ECU retards the timing which should get rid of the pinging. If your knock count is too high, you will really notice a huge performance loss and your engine at that point is at risk.

I got beat to write this thing and yes you need a logger of some sort to see your knock count.

 

[Quasimondo]

Here's a good article that explains detonation, pre-ignition, and the effects it has on an engine:
http://www.streetrodstuff.com/Articles/Engine/Detonation/