Air-to-air intercooler kit for Mazda RX7 — TA Technix

The turbo compresses air, and compression heats it up: 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, meaning less power. The intercooler cools it before it enters the engine.

The benefit is therefore less about top-end power than consistency: an original intercooler that has become heat-soaked lets power collapse on the second lap of a circuit or during the third acceleration. Beware of the instinct to go for the biggest one: excessive volume takes longer to fill and dulls response. The right intercooler maintains temperature throughout actual use.