What is detonation, and how can it be controlled?

Detonation is often referred to as engine knock. This condition occurs when fuel ignites early i.e. before the piston reaches the position where the spark ignition is scheduled. This means that the ignition explosion is trying to expand a cylinder chamber that is shrinking in size. When this firing pattern occurs it attempts to reverse the direction of the piston and the engine. When detonation occurs, the internal pneumatic forces of the piston can actually exceed 10x the normal forces acting upon a properly timed high performance engine. Early detonation is generally caused by excessive heat, extreme cylinder pressure, improper timing of the ignition system, inadequate fuel octane rating or a combination of these factors.

The most common factor that causes engine knock is excessive heat. Additional heat is produced in an engine as it generates an increased quantity of power. Today's pump gas only tolerates a finite amount of heat before it ignites. If this measure of heat is reached too early in the engine cycle it causes detonation. Although adding a supercharger to an engine rarely causes detonation it does create additional heat. A forced induction engine actually produces far less heat than a comparable normally aspirated high compression engine. To address the issue of increased heat an intercooler may be added to the supercharger system. An intercooler is a natural solution for forced induction and is included in many supercharger kits on the market today.

For engines currently experiencing detonation problems, the addition of an ignition/timing retard system, the use of higher octane fuel, or the addition of an intercooling solution may be used to address the issue. Ignition retard systems can be helpful in certain situations, but can greatly reduce the horsepower output of an engine. Any reduction in timing reduces horsepower. Reduction in timing can save a motor from detonation, but the excessive heat which was causing the detonation is still present. Intercooling is a more desirable option in most cases because it actually removes the heat which causes detonation, and allows higher boost levels to be safely run with full timing on pump gas. This setup produces the maximum benefit in terms of horsepower gains and engine protection, many times without additional maintenance or hassles.

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