# Detonation or pinging



## 142BHP (Jul 21, 2004)

Hi Guys

I have been working on my sr20 cylinder head and after much cursing I got her to run . We skimmed the head for a compression ratio of 11.5 to 1 but after I got the valves to seal properly there is a loud rattle when I advance the timing even slightly... I have the distributor turned all the way to the front of the car ( exhaust side of motor) just to get most of the noise away but still get the noise at very low rpm's at part throttle.

Should I install bigger injectors with the nissan management in the meantime to supply more fuel. At the moment I have to use 102.6 octane fuel to also help with the noise. I am installing a Mr Turbo management system that would take care of fueling and timing in the near future but I am afraid I might break something before the budget allows the management.

My compression tester gives a reading of about 185 psi on all cylinders and the guys around here reckon that is on the high side for 97 octane fuel.

I can best describe the noise as a rattle inside the engine , what is this detonation or pinging and also could someone please give the definition of both..

Thanks

Rudie


----------



## ddude2uc (Sep 7, 2005)

*Definitions*

*Detonation*
Detonation results when part of the unburned air-fuel mixture explodes violently. This is the most severe & engine damaging type of abnormal combustion.
Commonly referred to as spark knock or ping. Uncontrolled second explosion (after the spark occurs at the spark plug).
*Engine knock* is a syptom of detonation. The combustion chamber pressure rises so quickly that parts of the engine vibrate. Detonation sounds like a hammer hitting the side of the engine. Detonation can greatly increase the pressure & heat in the combustion chamber. Detonation damage includes cracked cylinder heads, blown head gaskets, burned pistons, & shattered spark plugs. 

*Preignition*
Preignition results when an overheated surface in the combustion chamber ignites the air/fuel mixture. Termed surface ignition, a "hot spot" (overheated bit of carbon, sharp metal edgde, hot exhaust vavle} causes the mixture to burn premeturely.

A *ping*, or mild knock, is a light tapping noise that can be heard during preignition. It is not as loud as or harmful as detonation knock.
Preigition is similar to detonation, but the action are reversed. Detonation begins _after_ the start of normal combustion. Preignition begins _before_ the start of normal combustion.


----------

