Air-to-air intercooler kit for Hyundai i30 III N-Performance — TA Technix

The turbo compresses air, and compression generates heat: at the compressor outlet, air can exceed 150°C. It is then less dense, meaning it contains less oxygen, and it causes knocking — which the ECU corrects by retarding the ignition, that is, reducing power. The intercooler cools it before it enters the engine.

The benefit is therefore not so much at peak power as in consistency: a saturated stock intercooler lets power collapse on the second lap of a circuit or during the third acceleration run. Beware of automatically choosing the biggest one: excessive volume takes longer to fill and dulls response. The right intercooler maintains temperature throughout real-world use.