What is Engine Detonation? Detonation is spontaneous combustion inside the cylinder AFTER the spark plug fires. It is similar to Pre-Ignition, but it is different. During normal ignition, the spark plug fires just before the piston reaches TDC. The flame travels across the combustion chamber igniting the Air/Fuel Mixture.
It is similar to Detonation, but it is different. When pre-ignition happens, something ignites the Air/Fuel Mixture d uring the Compression Stroke. This creates too much pressure inside the cylinder, too soon. The piston is then forced to compress already heated, expanding gases. Pre-ignition will cause significant damage without warning.
Detonation is the single most destructive force in a supercharged engine. This may include lowering boost level, retarding timing, installing a boost timing master, increasing fuel flow to prevent leanout, and/or using a fuel additive to raise octane level.
Aluminum heads will dissipate heat faster. This allows for higher Compression Ratios with less risk of Detonation. The cooler head also delivers a cooler air/fuel mixture to the combustion chamber. Cooler air is denser and can make more power. Cast iron heads will help the engine warm-up faster. This is good for drivability after a cold start.
Retarding the timing can help reduce Detonation. However, if the spark happens too late, you will lose power. This is because the cylinder pressure won't reach it's max until the piston is already headed back down on the Power Stroke. Engine damage and overheating can also be a problem. How is it controlled?
It creates turbulence, which forces the air/fuel mixture toward the spark plug. This reduces the possibility of Detonation. It also leads to cleaner emissions. What should it be? Quench should be as tight as possible, without the piston contacting the head. Recommended quench depends on your max rpm and the type of connecting rods you use.