The turbocharger compresses the air, and compression heats it up: at the compressor outlet, the air can exceed 150 °C. It is then less dense and therefore contains less oxygen, causing knock - which the ECU corrects by retarding the ignition, meaning less power. The intercooler cools the air before it enters the engine.

The benefit is therefore less about peak power than consistency: a saturated stock intercooler lets power drop sharply on the second lap of a track session or during the third acceleration run. Beware of automatically choosing the largest option: excessive volume takes longer to fill and blunts throttle response. The right intercooler keeps temperatures under control throughout your actual usage.