Air-to-air intercooler kit for Subaru Impreza WRX 1994-2000 — TA Technix

The turbo compresses air, and compression generates heat: at the compressor outlet, the 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, reducing power. The intercooler cools it before it enters the engine.

The benefit is therefore less about top-end power than consistency: an overheated stock intercooler lets power drop off on the second lap of a circuit 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 maintains stable temperatures throughout real-world use.