Blitz Type SE Front Mount Intercooler RX-7 '93-'95
A side effect of turbocharging is an increase in air temperature going into the engine. When the turbo creates boost and compresses the intake air, it's far too hot for maximum power. To overcome this problem, an intercooler (which utilizes a design similar to a radiator) is typically used. The intercooler is positioned between the turbo and engine and all the hot intake air that comes out of the turbo is cooled by the intercooler before it goes into the engine. This makes the intake charge more dense which equates to more power and helps to prevent detonation.
Picture is of a smaller Silvia intercooler. Actual RX-7 intercooler is bigger.