Detonation happens, and there's more than one reason why. ignition timing will do it. When spark timing is advanced too much, combustion chamber pressures can rise too high at the wrong time, resulting in minor explosions or pinging sounds we know as pre-ignition or detonation. It's like taking a hammer and whacking the tops of your pistons. Really hard. Low-octane gasoline will cause it too. Low-octane fuel burns faster than high-octane fuel, which can also result in too much chamber pressure given the right advanced spark, high-boost or high-compression circumstances. Lean air/fuel conditions, high engine temperatures and obstructions in the combustion chamber that act as hot spots will also lead to detonation. Detonation can make itself known through catastrophic engine damage, often times leaving sizeable peepholes in engine blocks or it can rear its damaging nature slowly, over time. Light detonation will gradually weaken pistons and piston rings, eventually causing them to fail. There's a fine line between the point at which an engine peaks horsepower-wise and the point at which rod bearings are smashed and pistons collapse. This dance along the ragged edge of detonation is what we call tuning. But while things like advanced ignition timing and leaner air/fuel conditions can cause detonation, they're also necessary when tuning for big horsepower.

Turbocharged engines typically exhibit much hotter intake temperatures in comparison to their naturally aspirated counterparts since the incoming air goes through a squishing process. Turbocharged combustion temperatures can also be much hotter. As boost levels increase, this only gets worse. Most turbocharged engines ward off the heat, which leads to detonation, by using an intercooler. Intercoolers, whether the air-to-air type or liquid-to-air type, drop the temperatures of the incoming air charge exiting the turbo's compressor before it enters the intake manifold. But intercoolers can only do so much and also have their negative side effects. As air travels through this heat exchanging process, it experiences a pressure drop; this is typically between 1 to 4 psi. And depending on the intercooler piping's shape, diameter and route taken, further restrictions are often placed on the intake charge. Besides, fitting an intercooler large enough for some particularly high-boost applications can often be impossible based on space constraints and weight factors.

Another way to ward off detonation is to increase the fuel supply through larger injectors or a higher volume pump. This works, and needs to be done, to the extent that air/fuel ratios are corrected. But a diminishing point is often reached, where fuel ends up being used to cool things off in the chamber rather than for combustion. At this point the risk of piston ring wear is fairly high and an alternative cooling method is in order. Too much fuel can also slow down the burn process, making for a relatively safe, but not so powerful engine.