whats pinking? ive asked before but cant remember.
Pinking is spontaneous combustion caused by pre-ignition, which itself is caused by excessive heat. The maximum pressure in the combustion chamber should be reached after TDC at the start of the power stroke. Causes for the excessive heat source could be a number of things.
Hot spots in the combustion chamber, ie spark plug electrodes, carbon deposits etc.
The wrong grade of fuel being used, ie 95 instead of 98. In old money, the higher the octane rating, the more TEL (tetra ethyle lead) was added to the fuel. Lead helps delay the onset of detonation, allowing higher compression ratios to be used, thus higher combustion temperatures. High altitude piston engined bombers of WWII used to use 130octane fuel with water injection. Lead has now been replaced by another substance which has escaped my memory.
Ignition timing being too far advanced, (pre-ignition effectively) causing the max pressure in the cylinders occuring before TDC rather than after.
Too lean a mixture. This is important as fuel is a volatile liquid, ie it gives itself up as a gas very readily. This is because it is cold, and it is the coldness of the fuel, and how much of it there is that detrmins how hot the combustion is. As said before, excessive heat leads to detonation. If you go the other way, and have a rich mixture, not all of the charge will be burned as there is not sufficient heat to burn it all. (Indicated by sooty black smoke from the exhaust. This is unburned fuel) Bear one thing in mind. The fuel is supplied to burn the oxygen to expand the nitrogen in the charge.
Master class over. I hope you understood it.
