Team-BHP - Intercool and Turbos

what does intercool do to improve the performance...
well i know some stuff about turbos...but not intercool...
what will be the boost i will be getting...
will it affect the millage to a big extend or will it increase as i heard when you install Turbo it Increases the millaga a Bit...

*****How much will it cost to install turbo and intercool on my Nissan bluebird 1.8 Petrol...
nothing too fancy / expensive...

First of all you should know that a TURBO is used to push in more air into an engine, when more air is sucked and pushed into a small area like in the tube connected turbo to the throttle body, air is heated up due to friction between air molecules and because of heat there is less % of oxygen in the compressed air and mind you oxygen is necessary for combustion. another effect of compressed air is pre ignition of fuel when fuel and air is mixed because the air is hot. so charge (air + fuel mixture ) burns inside the cylinder even before the piston comes up and before the spark plug fires this is known as pinging and this damages the ports on the cylinder and also there is loss of power. to reduce the heat of the pressurised air from the turbo, an intercooler is placed between the turbo and the engine. inter cooler is like a radiator which radiates heat by flowing through small fins. This is placed below the front bumper where there is cool air blowing.
see this link on how turbo and inter cooler works : http://www.mazdarotary.net/turbo.htm
-shaz