Hey guys,
I am 16 years old, I know a good deal about cars, but I am wondering, what is this ping and knock stuff that people talk about when they hear their engines run? What does it sound like? Sorry I don't mean to sound like a dumbA$$

 

Put a marble or bolt in a tin can, and shake it kinda slowly/unevenly. 'bout the best way I've heard it described.

 

Detonation is uncontrolled rapid spontanious combustion
(explosion) if the air fuel charge. [rapid pressure and temp rise]
Normal combustion is a burning at a set rate of the air/fuel
starting at the spark plug and progressing across the combustion chamber.
All fuels have an auto ignition point {temp} at which they will light off by them selves.
A fuels ability to resist autoignition (knock) is refered as its
octane rating.

 

but not as smooth... if that is possible.

and it only does it when the motor is under a load..

 

oh, it can do it when the motor's not under load.. i hear it all the time at stop lights sittin next to some ghetto rides.

that is, unless the latest fad is to stick a diesel motor in...

 

2 ways to stop it .Better fuel or change the timimng. It is not rare to hear it at a stop light.

 

detonation happens under load.. if you hear it at idle, its preignition and the car is a POS.

 

Exactly. During the summer when I am driving up some long grades (we have lots of hills here) I occasionally will hear the car in the other lane beside me "pinging" while going up the hill. This is the most common time you are apt to hear detonation besides WOT.

If it is happening during idle or part-throttle cruise on a flat road, there is something wrong.

And the description "sounds like a bunch of marbles rattling around in a tin-can" is probably the closest sound.